Make Electronics Book Learning by Discovery

Make Electronics Book Learning by Discovery
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Make Electronics Book Learning by Discovery

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    Make: Electronics

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    Make: ElectronicsLearning by DiscoveryCharles Plattwith photographs and illustrations by the authorBeijing • Cambridge • Farnham • Köln • Sebastopol • Taipei • Tokyo

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    Make: Electronicsby Charles PlattCopyright © Helpful Corporation. All rights reserved. Printed in Canada.Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472.O’Reilly Media books may be purchased for educational, business, or sales promotional use. Online e...

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    For my dearest Erico

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    vii 10, 10,Preface. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,. 10,ix 16,1. 16,ExperiencingElectric...

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    Contentsviii 162,4. 162,Chips,Ahoy!. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,. 162,147 162,Shopping List: Experim...

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    ix PrefaceHow to Have Fun with This BookEveryone uses electronic devices, but most of us don’t really know what goes on inside them. Of course, you may feel that you don’t need to know. If you can drive a car without understanding the workings of an internal combustion engine, pre-sumably you...

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    How Hard Will It Be? PrefacexLearning by discovery occurs in serious research, when scientists notice an un-usual phenomenon that cannot be explained by current theory, and they start to investigate it in an effort to explain it. This may ultimately lead to a better understanding of the world. We...

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    PrefacexiFundamentalsMoving Through This Book Basically there are two ways to present information in a book of this kind: in tutorials and in reference sections. I’m going to use both of these methods. You’ll find the tutorials in sections headed as follows: • Shopping Lists • Using Tool...

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    FundamentalsPrefacexiiactionURI(http://www.newark.com):http://www.newark.com Newark. Mouser, Digi-Key, and Newark are all good sources for components, usually requiring no minimum quantities.actionURI(http://www.allelectronics.com):http://www.allelectronics.com All Electronics Corporation. A narr...

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    PrefacexiiiSafari® Books OnlineCompanion KitsMaker Shed actionURI(http://www.makershed.com):(www.makershed.com) offers a number of MactionURI(http://www.makershed.com):ake:actionURI(http://www.makershed.com): ElectronicsactionURI(http://www.makershed.com): companion kits, both toolkitsactionURI...

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    11Experiencing ElectricityI want you to get a taste for electricity—literally!—in the first experiment. This first chapter of the book will show you: • How to understand and measure electricity and resistance• How to handle and connect components without overloading, damaging, or destroyi...

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    Shopping List: Experiments 1 Through 5 Chapter 12Wire cutters RadioShack Kronus 4.5-inch, part number 64-2951, or Stanley 7-inch model 84-108. Or similar. Use them for cutting copper wire, not harder metals (Figure 1-4). Figure 1-1. Generic long-nosed pliers are your most fundamen-tal tool for gr...

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    Experiencing Electricity3Shopping List: Experiments 1 Through 5 On a manual-ranging meter, you select the range, and if the source that you are measuring is outside of that range, the meter tells you that you made an error. I prefer this. I also get impatient with the time it takes for the autora...

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    Shopping List: Experiments 1 Through 5 Chapter 14Battery holder for four AA cells, with wires attached (Figure 1-10). Quan-tity: 1. All Electronics catalog number BH-342 or RadioShack part 270-391 or similar.Alligator clipsVinyl-insulated. Quantity: at least 6. All Electronics catalog number ALG-...

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    Experiencing Electricity5Experiment 1: Taste the Power!Experiment 1: Taste the Power!Can you taste electricity? Maybe not, but it feels as if you can.You will need:• 9-volt battery• Snap connector for battery terminals • MultimeterProcedureMoisten your tongue and touch the tip of it to the ...

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    Experiment 1: Taste the Power!Chapter 16If you make a mistake and try to measure something inappropriate, the meter will show you an error message such as “E” or “L.” Turn the dial and try again.Figure 1-18Figure 1-19Figure 1-20. To measure resistance and voltage, plug the black lead into...

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    Experiencing Electricity7Experiment 1: Taste the Power!ProcedureWe’re going to use the meter to discover the electrical resistance of your tongue. First, set your meter to measure resistance. If it has autoranging, look to see whether it is displaying a K, meaning kilohms, or M, meaning megohm...

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    Experiment 1: Taste the Power!Chapter 18BAckgroundThemanwhodiscoveredresistanceGeorg Simon Ohm, pictured in Figure 1-27, was born in Bavaria in 1787 and worked in obscurity for much of his life, studying the nature of electricity using metal wire that he had to make for himself (you couldn’t tr...

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    Experiencing Electricity9Experiment 2: Let’s Abuse a Battery!CleanupandRecyclingYour battery should not have been damaged or significantly discharged by this experiment. You’ll be able to use it again. Remember to switch off your meter before putting it away.Experiment 2: Let’s Abuse a Batt...

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    Experiment 2: Let’s Abuse a Battery!Chapter 110The heat is caused by electricity flowing through the wires and through the electrolyte (the conductive fluid) inside the battery. If you’ve ever used a hand pump to force air into a bicycle tire, you know that the pump gets warm. Elec-tricity be...

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    Experiencing Electricity11Experiment 2: Let’s Abuse a Battery!First inspect the fuse very carefully, using a magnifying glass if you have one. You should see a tiny S-shape in the transparent window at the center of the fuse. That S is a thin section of metal that melts easily. Remove the batte...

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    Experiment 2: Let’s Abuse a Battery!Chapter 112FundAmentAlsDirectandalternatingcurrentThe flow of current that you get from a battery is known as direct current, or DC. Like the flow of water from a faucet, it is a steady stream, in one direction.The flow of current that you get from the “hot...

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    Experiencing Electricity13Experiment 3: Your First CircuitCleanupandRecyclingThe first AA battery that you shorted out is probably damaged beyond repair. You should dispose of it. Putting batteries in the trash is not a great idea, be-cause they contain heavy metals that should be kept out of the...

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    Experiment 3: Your First CircuitChapter 114FundAmentAlsDecodingresistorsSome resistors have their value clearly stated on them in microscopic print that you can read with a magnifying glass. Most, however, are color-coded with stripes. The code works like this: first, ignore the color of the body...

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    Experiencing Electricity15Experiment 3: Your First CircuitFundAmentAlsDecodingresistors(continued)Note that the color-coding is consistent, so that green, for instance, means either a value of 5 (for the first two stripes) or 5 zeros (for the third stripe). Also, the sequence of colors is the sam...

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    Experiment 3: Your First CircuitChapter 116LightinganLEDNow take a look at one of your LEDs. An old-fashioned lightbulb wastes a lot of power by converting it into heat. LEDs are much smarter: they convert al-most all their power into light, and they last almost indefinitely—as long as you trea...

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    Experiencing Electricity17Experiment 3: Your First CircuitNow swap out your 2K resistor and substitute a 1K resistor, which will have brown-black-red stripes, meaning 1-0 and two more zeros. The LED should glow more brightly.Swap out the 1K resistor and substitute a 470Ω resistor, which will hav...

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    Experiment 4: Varying the VoltageChapter 118Experiment 4: Varying the VoltagePotentiometers come in various shapes and sizes, but they all do the same thing: they allow you to vary voltage and current by varying resistance. This experiment will enable you to learn more about voltage, amperage, an...

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    Experiencing Electricity19Experiment 4: Varying the Voltagepossesses some resistance (a total of 2K in this instance), and as you turn the shaft of the potentiometer, a wiper rubs against the resistance, giving you a shortcut to any point from the center terminal. You can try to put it back toget...

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    Experiment 4: Varying the VoltageChapter 120While the batteries are connected to the circuit, set your meter to measure volts DC as shown in Figures 1-52 through 1-54. Now touch the probes either side of the LED. Try to hold the probes in place while you turn the potentiometer up a little, and do...

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    Experiencing Electricity21Experiment 4: Varying the Voltage6v Battery PackVoltsFigure 1-56. The meter shows how much voltage the LED takes.6v Battery PackVoltsFigure 1-57. The meter shows how much voltage the potentiometer takes. CheckingtheFlowNow I want you to make a different measurement. I w...

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    Experiment 4: Varying the VoltageChapter 122Figure 1-58. Any meter will blow its internal fuse if you try to make it measure too high an amperage. In our circuit, this is not a risk as long as you keep the potentiometer in the middle of its range. Choose “mA” for milliamps and remember that t...

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    Experiencing Electricity23Experiment 4: Varying the VoltageIt’s time now to nail this down with some numbers. Here’s one last thing to try. Set aside the LED and substitute a 1KΩ resistor, as shown in Figure 1-64. The total resistance in the circuit is now 1KΩ plus whatever the resistance t...

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    Experiment 4: Varying the VoltageChapter 1246v Battery PackAmpsFigure 1-64. If you substitute a resistor instead of the LED, you can confirm that the cur-rent flowing through the circuit varies with the total resistance in the circuit, if the voltage stays the same.Turn the potentiometer all the ...

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    Experiencing Electricity25Experiment 4: Varying the VoltageIn fact, we could say:voltage = kilohms × milliampsBut wait a minute: 1K is 1,000 ohms, and 1mA is 1/1,000 of an amp. Therefore, our formula should really look like this:voltage = (ohms × 1,000) × (amps/1,000)The two factors of 1,000 c...

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    Experiment 4: Varying the VoltageChapter 126UsingOhm’sLawOhm’s Law is extremely useful. For example, it helps us to figure out whether a component can be used safely in a circuit. Instead of stressing the component until we burn it out, we can predict whether it will work. For instance, the f...

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    Experiencing Electricity27Experiment 4: Varying the VoltageBAckgroundHowmuchvoltagedoesawireconsume?Normally, we can ignore the resistance in electric wires, such as the little leads of wire that stick out of resistors, because it’s trivial. However, if you try to force large amounts of current...

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    Experiment 4: Varying the VoltageChapter 128Here’s an example. Suppose I want a red LED, such as the Vishay part TLHR5400, which has become such a common item that I can buy them individually for 9 cents apiece. I click the link to the data sheet maintained by the manufacturer, Vishay Semicondu...

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    Experiencing Electricity29Experiment 4: Varying the VoltageWe want to know R, the resistance. So, we use the version of Ohm’s Law that puts R on the left side:R= V/INow plug in the values:R = 3.5/0.02Run this through your pocket calculator if you find decimals confusing. The answer is:R = 175Ω...

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    Experiment 4: Varying the VoltageChapter 130theoryDoingthemathonyourtongueI’m going to go back to the question I asked in the previous experiment: why didn’t your tongue get hot?Now that you know Ohm’s Law, you can figure out the answer in numbers. Let’s suppose the battery delivered its ...

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    Experiencing Electricity31Experiment 4: Varying the VoltageFundAmentAlsWattbasicsSo far I haven’t mentioned a unit that everyone is familiar with: watts.A watt is a unit of work. Engineers have their own definition of work—they say that work is done when a person, an animal, or a machine push...

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    Experiment 5: Let’s Make a BatteryChapter 132Experiment 5: Let’s Make a BatteryLong ago, before web surfing, file sharing, or cell phones, kids were so horribly deprived that they tried to amuse themselves with kitchen-table experiments such as making a primitive battery by pushing a nail and...

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    Experiencing Electricity33Experiment 5: Let’s Make a BatterytheoryThenatureofelectricityTo understand electricity, you have to start with some basic information about atoms. Each atom consists of a nucleus at the center, containing protons, which have a positive charge. The nucleus is surrounde...

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    Experiment 5: Let’s Make a BatteryChapter 134How much current is being generated in your lemon battery? Set your meter to measure milliamps, and connect it between the nail and the penny. I mea-sured about 2mA, but got 10mA when I used some #10 stranded copper wire instead of a penny and a larg...

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    Experiencing Electricity35Experiment 5: Let’s Make a BatteryBAckgroundPositiveandnegativeIf electricity is a flow of electrons, which have a negative charge, why do people talk as if electricity flows from the positive terminal to the negative terminal of a battery?The answer lies in a fundamen...

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    Experiment 5: Let’s Make a BatteryChapter 136theoryBasicmeasurementsElectrical potential is measured by adding up the charges on individual electrons. The basic unit is the coulomb, equal to the total charge on about 6,250,000,000,000,000,000 electrons.If you know how many electrons pass throug...

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    Experiencing Electricity37Experiment 5: Let’s Make a BatteryPracticallySpeakingFor practical purposes, an intuitive understanding of electricity can be more useful than the theory. Personally I like the water analogies that have been used for decades in guides to electricity. Figure 1-77 shows ...

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    Experiment 5: Let’s Make a BatteryChapter 138SameresistanceHigher voltage Greater forcecreates more flow,because amperage =voltage / resistance,and the voltage hasgone up, whilethe resistancehas remainedthe same.Higher water levelFigure 1-79. Greater force generates more flow, as long as the re...

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    239Switching Basics and MoreThe concept of switching is fundamental in electronics, and I’m not just talking about power switches. By “switching,” I mean using one flow of electricity to switch, or control, another. This is such an important principle that no digital device can exist withou...

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    Shopping List: Experiments 6 Through 11Chapter 240Figure 2-2. This “breadboard” for quickly constructing electronic circuits has a metal base, and screw terminals for attaching wires from a power supply.Figure 2-3. A breadboard without screw terminals is almost as convenient, and is cheaper.T...

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    Switching Basics and More41Shopping List: Experiments 6 Through 11SuppliesHookup wireSolid-conductor, 22-gauge, minimum 25 feet of each color. See Figure 2-6. Part 278-1222 from RadioShack, catalog item 9948T17 from McMaster-Carr, or check eBay for deals. It’s easy to buy the wrong kind of wire...

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    Shopping List: Experiments 6 Through 11Chapter 242ComponentsPushbuttonMomentary-on, SPST, sometimes referred to as OFF-(ON) or (ON)-OFF type. Must be PCB- or PC-mount, meaning is extremely small with thin spiky contacts on the bottom. Quantity: 1. See Figure 2-11.Examples are part number AB11AP b...

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    Switching Basics and More43Experiment 6: Very Simple SwitchingCeramic capacitors, assorted. Make sure you get at least one rated at 0.0047 μF (which can also be written as 47 nF). See Figure 2-15.ResistorsIf you bought only a minimal selection for experiments 1 through 5, now’s the time to buy...

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    Experiment 6: Very Simple SwitchingChapter 2446v Battery PackShortLED leadLong LED leadFigure 2-17. If the LED is on, flipping either of the switches will turn it off. If the LED is off, either of the switches will turn it on. Use alligator clips to attach the wires to each other, and to the swit...

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    Switching Basics and More45Experiment 6: Very Simple SwitchingFigure 2-20. To remove insulation from the end of a thin piece of wire, you can also use wire cutters. This takes a little practice.Figure 2-21. Those who tend to misplace tools, and feel too impatient to search for them, may feel temp...

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    Experiment 6: Very Simple SwitchingChapter 246FundAmentAlsAllaboutswitchesWhen you flip the type of toggle switch that you used in 58,Experiment 6, it connects the center terminal with one of the outer terminals. Flip the switch back, and it connects the center terminal with the other outer term...

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    Switching Basics and More47Experiment 6: Very Simple SwitchingFundAmentAlsAllaboutswitches(continued)Figure 2-27. These are all toggle switches. Generally, the larger the switch, the more current it can handle.To make things more interesting, you can also buy switches that have three or four pole...

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    Experiment 6: Very Simple SwitchingChapter 248FundAmentAlsAllaboutswitches(continued)SparkingWhen you make and break an electrical connection, it tends to create a spark. Sparking is bad for switch contacts. It eats them until the switch doesn’t make a reliable connection anymore. For this reas...

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    Switching Basics and More49Experiment 6: Very Simple SwitchingBAckgroundEarlyswitchingsystemsSwitches seem to be such a fundamental feature of our world, and their concept is so simple that it’s easy to forget that they went through a gradual process of development and refinement. Primitive kni...

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    Experiment 6: Very Simple SwitchingChapter 250IntroducingSchematicsIn Figure 2-35, I’ve redrawn the circuit from 58,Experiment 6 in a simplified style known as a “schematic.” From this point onward, I will be illustrating circuits with schematics, because they make circuits easier to under...

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    Switching Basics and More51Experiment 6: Very Simple SwitchingFundAmentAlsBasicschematicsymbolsSchematic symbols are like words in a language: they have mutated over the years into a confusing range of variations. A simple on/off (single-pole, single-throw, or SPST) switch, for instance, can be r...

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    Experiment 6: Very Simple SwitchingChapter 252FundAmentAlsBasicschematicsymbols(continued)The problem is that this is not very intuitive, especially when you’re just beginning to use schematics. When you see two wires crossing, you can easily imagine that they are making a connection, even thou...

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    Switching Basics and More53Experiment 6: Very Simple SwitchingFundAmentAlsBasicschematicsymbols(continued)Potentiometers suffer from the same inconsistent style be-tween the United States and Europe, but either way, you’ll find an arrow showing where the wiper (usually, the center terminal) tou...

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    Experiment 6: Very Simple SwitchingChapter 254FundAmentAlsBasicschematicsymbols(continued)For example, the three LED circuits that I have included in Figure 2-47 show components in different positions, using dif-ferent symbols, but all three circuits function exactly the same way, because their c...

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    Switching Basics and More55Experiment 7: Relay-Driven LEDsExperiment 7: Relay-Driven LEDsYou will need:• AC adapter, wire cutters and strippers.• DPDT relay. Quantity: 2.• LEDs. Quantity: 2.• Resistor, 680Ω approx. Quantity: 1.• Pushbutton, SPST. Quantity: 1.• Hookup wire, 22 gauge, ...

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    Experiment 7: Relay-Driven LEDsChapter 2561. It’s important to make sure that your AC adapter is not plugged into the wall!2. Chop off the little plug at the end of its wire. See Figure 2-49.3. Use a box cutter or utility knife or scissors to make a half-inch cut between the two conductors, and...

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    Switching Basics and More57Experiment 7: Relay-Driven LEDsABCDDFigure 2-51. This is one way that the parts inside a relay can be arranged. The coil, A, gener-ates a magnetic attraction pulling lever B downward. A plastic extension, C, pushes outward against flexible metal strips and moves the pol...

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    Experiment 7: Relay-Driven LEDsChapter 258FundAmentAlsInsidearelayA relay contains a coil of wire wrapped around an iron core. When electricity runs through the coil, the iron core exerts a magnetic force, which pulls a lever, which pushes or pulls a springy strip of metal, closing two contacts. ...

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    Switching Basics and More59Experiment 7: Relay-Driven LEDsProcedureTurn the relay with its legs in the air and attach wires and LEDs as shown in Figure 2-59, with a 680Ω resistor (a 1K resistor will be OK if you don’t have the correct value). Also attach a pushbutton switch. (Your pushbutton s...

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    Experiment 8: A Relay OscillatorChapter 260Experiment 8: A Relay OscillatorYou will need:• AC adapter, breadboard, wire, wire cutters and strippers.• DPDT relay. Quantity: 1.• LEDs. Quantity: 2.• Pushbutton, SPST. Quantity: 1.• Alligator clips. Quantity: 8.• Resistor, approximately 68...

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    Switching Basics and More61Experiment 8: A Relay OscillatorAddingCapacitanceAdd a 1,000 μF electrolytic capacitor in parallel with the coil of the relay as shown in the diagram in Figure 2-65 and the schematic in Figure 2-66. Check Figure 2-14 if you’re not sure what a capacitor looks like. Th...

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    Experiment 8: A Relay OscillatorChapter 262FundAmentAlsCapacitorbasicsDC current does not flow through a capacitor, but voltage can accumulate very quickly inside it, and remains after the power supply is disconnected. Figures 2-67 and 2-68 may help to give you an idea of what happens inside a ca...

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    Switching Basics and More63Experiment 8: A Relay OscillatorFundAmentAlsCapacitorbasics(continued)Ceramic capacitors have no polarity, meaning that you can apply negative volt-age to either side of them. Electrolytics do have polarity, and won’t work unless you connect them the right way around....

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    Experiment 8: A Relay OscillatorChapter 264BAckgroundMichaelFaradayandcapacitorsThe earliest capacitors consisted of two metal plates with a very small gap between them. The principle of the thing was simple:• If one plate was connected to a positive source, the positive charges at-tracted nega...

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    Switching Basics and More65Experiment 8: A Relay OscillatorBreadboardingtheCircuitI promised to free you in time from the frustrations of alligator clips, and that time has come. Please turn your attention to the block of plastic with lots of little holes in it that I asked you to buy. For reason...

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    Experiment 8: A Relay OscillatorChapter 266Important note: some breadboards divide each vertical column of holes, on the left and the right, into two separate upper and lower sections. Use your meter’s continuity testing feature to find out if your breadboard conducts power along its full lengt...

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    Switching Basics and More67Experiment 8: A Relay OscillatorYou’ll need some more 22-gauge wire, or some precut hookup wire, to supply the power to your components, which are plugged into the breadboard as shown in Figures 2-76 and 2-77. If you get all the connections right, the circuit should f...

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    Experiment 9: Time and CapacitorsChapter 268Experiment 9: Time and CapacitorsYou will need:• AC adapter, breadboard, wire, wire cutters, and strippers.• Multimeter.• Pushbutton, SPST. Quantity: 1.• Resistors and electrolytic capacitors, assorted.In 75,Experiment 8, when you put a capacit...

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    Switching Basics and More69Experiment 9: Time and CapacitorsRelease the pushbutton, set aside your meter, and discharge the capacitor by touching R2 across it for a second or two. Now substitute a 50K resistor for R1, and repeat the measurement. The meter should count upward almost twice as fast ...

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    Experiment 9: Time and CapacitorsChapter 270difference between one end of the resistor and the other will be zero (assum-ing that we ignore little imperfections in the components). Figure 2-80 may help to clarify this concept.1K1K12vDC6volts6volts1K9K12vDC1.2volts10.8volts1K99K12vDC0.12volts11.88...

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    Switching Basics and More71Experiment 9: Time and CapacitorstheoryThetimeconstantYou may be wondering if there’s a way to predict exactly how much time it takes for various capacitors to charge, when they are paired with various resistors. Is there a for-mula to calculate this?Of course, the an...

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    Experiment 9: Time and CapacitorsChapter 272theoryThetimeconstant(continued)The cake eater will always have a few crumbs to eat, be-cause he never takes 100% of the remainder. Likewise, the capacitor will never acquire a full charge. In a perfect world of perfect components, this process would co...

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    Switching Basics and More73Experiment 10: Transistor SwitchingExperiment 10: Transistor SwitchingYou will need:• AC adapter, breadboard, wire, and meter.• LED. Quantity: 1.• Resistors, various.• Pushbutton, SPST. Quantity: 1.• Transistor, 2N2222 or similar. Quantity: 1.A transistor can ...

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    Experiment 10: Transistor SwitchingChapter 274Initially, the LED should be dark. Now press the pushbutton and the LED should glow brightly. Electricity is following two paths here. Look at the schematic in Figure 2-86, which shows the same circuit more clearly. I’ve shown positive at the top an...

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    Switching Basics and More75Experiment 10: Transistor SwitchingYour finger is conducting positive voltage to the base of the transistor. Even though your skin has a high resistance, the transistor still responds. It isn’t just switching the LED on and off; it is amplifying the current applied to...

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    Experiment 10: Transistor SwitchingChapter 276essentIAlsAllaboutNPNandPNPtransistorsA transistor is a semiconductor, meaning that sometimes it conducts electricity, and sometimes it doesn’t. Its internal resistance varies, depending on the power that you apply to its base. NPN and PNP transisto...

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    Switching Basics and More77Experiment 10: Transistor SwitchingessentIAlsAllaboutNPNandPNPtransistors(continued)All-transistorbasics• Never apply a power supply directly across a transistor. You can burn it out with too much current.• Protect a transistor with a resistor, in the same way you w...

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    Experiment 10: Transistor SwitchingChapter 278BAckgroundTransistororiginsThough some historians trace the origins of the transistor back to the inven-tion of diodes (which allow electricity to flow in one direction while preventing reversal of the flow), there’s no dispute that the first workin...

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    Switching Basics and More79Experiment 10: Transistor SwitchingessentIAlsTransistorsandrelaysOne limitation of NPN and PNP transistors is that they are naturally “off” until you turn them “on.” They behave like a normally open pushbutton, which conducts electricity only for as long as you ...

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    Experiment 10: Transistor SwitchingChapter 280theorySeethecurrentIf you want to get a more precise understanding of how a transistor works, you should try this little test. It shows the precise behavior and limits of the 2N2222 transistor that you used in the previous experiment.I’ve said that ...

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    Switching Basics and More81Experiment 10: Transistor SwitchingtheorySeethecurrent(continued)In my little experiment, I found that the maximum cur-rent at A2 was 33mA. A simple calculation using Ohm’s Law showed me that this meant the transistor’s internal resistance was near zero. This is why...

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    Experiment 11: A Modular ProjectChapter 282Experiment 11: A Modular ProjectYou will need:• AC adapter, breadboard, wire, and meter.• LED. Quantity: 1.• Resistors, various.• Capacitors, various.• Transistor, 2N2222 or similar. Quantity: 2.• 2N6027 programmable unijunction transistor (P...

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    Switching Basics and More83Experiment 11: A Modular ProjectessentIAlsAllaboutprogrammableunijunctiontransistorsThe schematic symbol for a programmable unijunction transistor, or PUT, looks very different from the symbol for a bipolar transistor, and its parts are named differently, too. Neverthel...

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    Experiment 11: A Modular ProjectChapter 284essentIAlsAllaboutprogrammableunijunctiontransistors(continued)This may cause you to wonder what the function of the gate is. You can think of it as “assisting” the finger on the button. In fact, the gate is the “programmable” part of a PUT. By c...

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    Switching Basics and More85Experiment 11: A Modular ProjectStep1:Slow-SpeedOscillationFigure 2-103 is a schematic version of the previous PUT breadboard circuit shown in Figure 2-98, drawn so that the layout looks as much like the bread-board as possible.15K470K27K2N60272.2uF6VDCFigure 2-103. Thi...

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    Experiment 11: A Modular ProjectChapter 286Step2:BeyondthePersistenceofVisionIf you substitute a much smaller capacitor, it will charge much more quickly, and the LED will flash faster. Suppose you use a capacitor of 0.0047 μF (which can also be expressed as 47 nanofarads, or 47 nF). This seems ...

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    Switching Basics and More87Experiment 11: A Modular ProjectI want you to keep the slow-flashing circuit separately, untouched, because I have an idea to make use of it a little later. You can leave the LED blinking.The loudspeaker should be wired in series with a 100Ω resistor to limit the cur-r...

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    Experiment 11: A Modular ProjectChapter 288R1R2R3Q1Q3C1D1R4R7Q2C2L1R8R5R66VDCFigure 2-107. By adding a 2N2222 general-purpose transistor, we amplify the signal from Q2: R8: 1K Q3: 2N2222 Other components are the same as in the previous step in constructing this circuit.10033K15K470K27K2.2uF....

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    Switching Basics and More89Experiment 11: A Modular ProjectR1R2R3Q1Q3Q4C1D1R4R9R7Q2C2L1R5R8R66VDCFigure 2-109. Q4 is another 2N2222 transistor that further amplifies the signal. It receives power through R9: 2.2K.1002K21K2N60272N22222N222233K15K470K27K2.2uF.0047uF27K470K2N60276VDCFigure 2-110. Th...

  • Page 105

    Experiment 11: A Modular ProjectChapter 290Step4:PulsedOutputIf you wanted to use this audio signal as some kind of an alarm, a steady dron-ing noise is not very satisfactory. A pulsing output would be a much better attention-getter. Well, the first section of the circuit that you assembled creat...

  • Page 106

    Switching Basics and More91Experiment 11: A Modular ProjectR1R2R3R10R6Q1Q3Q4C1C3R4R9R7Q2C2L1R8R56VDCFigure 2-113. R10 connects the slow-running oscillator at the top of the breadboard to the gate of Q2, the PUT in the middle of the breadboard. This modulates the audio oscillator, with addition of...

  • Page 107

    Experiment 11: A Modular ProjectChapter 292TweakingitThere’s still a lot of room for creativity here:• Adjust the frequency of the sound: Use a smaller or larger capacitor in-stead of C2 (half or twice the current value). Use a smaller or larger value for R5.• Adjust the pulsing feature: Us...

  • Page 108

    Switching Basics and More93Experiment 11: A Modular Project4. If the alarm is triggered, what then? If someone forces open a window, should the alarm stop sounding as soon as the window is closed again? No, the alarm should lock itself on, until you turn it off. 5. How do you turn it off? Some ki...

  • Page 109

  • Page 110

    395Getting Somewhat More SeriousI don’t know how far you’ll want to delve into electronics, but I do know that I’ve shown you about as much as I can with just a handful of components, some wires, a breadboard, and a few tools. To continue, you’ll need:• Some more tools and supplies• B...

  • Page 111

    Shopping List: Experiments 12 Through 15Chapter 396I am assuming that you already have some commonly used workshop basics, such as an electric drill.Essential: Pencil-type 15-watt soldering ironExamples are RadioShack part 64-2051, McMaster-Carr catalog item 7016A34, or Xytronic model 252. See Fi...

  • Page 112

    Getting Somewhat More Serious97Shopping List: Experiments 12 Through 15Figure 3-4. As long as you treat it carefully, a cheap set of plastic magnifying lenses is perfectly acceptable. Handheld magnifica-tion is essential for inspecting the solder joints that you make on perforated board.Figure 3-...

  • Page 113

    Shopping List: Experiments 12 Through 15Chapter 398Essential: Heat gunAfter you join two wires with solder, you often need to insulate them. Electrical tape, sometimes called insulating tape, is messy and tends to come unstuck. You’ll be using heat-shrink tube, which forms a safe, per-manent s...

  • Page 114

    Getting Somewhat More Serious99Shopping List: Experiments 12 Through 15Recommended: Miniature hand sawI assume that you will want to mount a finished electronics project in a de-cent-looking enclosure. Consequently, you are likely to need tools to cut, shape, and trim thin plastic. For example, y...

  • Page 115

    Shopping List: Experiments 12 Through 15Chapter 3100I like Mitutoyo calipers, and the low-end model 505-611 (shown in Figure 3-19) does everything I need. You can find cheaper brands, but economiz-ing on precision measuring tools may not be a wise policy in the long term. The manufacturer’s sit...

  • Page 116

    Getting Somewhat More Serious101Shopping List: Experiments 12 Through 15from Lowe’s, Home Depot, Ace Hardware, and similar stores. You’ll decide how much to buy after you measure the distances between the magnetic sensor switches that you decide to install.Heat-shrink tubeFor use in conjuncti...

  • Page 117

    Shopping List: Experiments 12 Through 15Chapter 3102Figure 3-24. A larger example of perforated board with breadboard geometry.Figure 3-25. Plain perforated board (with no copper traces) can be used for mount-ing components when you want to do point-to-point wiring.Figure 3-26. A small piece of p...

  • Page 118

    Getting Somewhat More Serious103Shopping List: Experiments 12 Through 15ComponentsPower plugs, sockets, and binding postsAfter you finish a project and put it in a box, you’ll need a convenient way to supply it with power. Buy yourself a pair of insulated binding posts, such as RadioShack part ...

  • Page 119

    Experiment 12: Joining Two Wires TogetherChapter 3104LoudspeakerTo complete the project in 142,Experiment 15, you’ll need a loudspeaker small enough to fit inside your project box but louder than the 1-inch speaker that you used previously. It should be 2 inches or 2.5 inches (50 to 60 mm) in ...

  • Page 120

    Getting Somewhat More Serious105Experiment 12: Joining Two Wires TogetherNow follow these steps (shown in Figures 3-32 through 3-36):1. Make sure the tip of the soldering iron is clean (wipe it on the moist-ened sponge in the base of your helping hand if necessary), then touch it against the inte...

  • Page 121

    Experiment 12: Joining Two Wires TogetherChapter 3106BAckgroundSolderingmythsMyth #1: Soldering is very difficult.Millions of people have learned how to do it, and statis-tically, you are unlikely to be less coordinated than all of them. I have a lifelong problem with a tremor in my hands that ma...

  • Page 122

    Getting Somewhat More Serious107Experiment 12: Joining Two Wires TogethertoolsEightmostcommonsolderingerrors1. Not enough heat. The joint looks OK, but because you didn’t apply quite enough heat, the solder didn’t melt sufficiently to realign its internal molecular structure. It remained gran...

  • Page 123

    Experiment 12: Joining Two Wires TogetherChapter 3108YourSecondSolderJointTime now to try your pencil-style soldering iron. Once again, you must leave it plugged in for a good five minutes to make sure it’s hot enough. In the mean-time, don’t forget to unplug your other soldering iron, and pu...

  • Page 124

    Getting Somewhat More Serious109Experiment 12: Joining Two Wires TogethertheorySolderingtheoryThe better you understand the process of soldering, the easier it should be for you to make good solder joints.The tip of the soldering iron is hot, and you want to transfer that heat into the joint that...

  • Page 125

    Experiment 12: Joining Two Wires TogetherChapter 3110AddingInsulationAfter you’ve succeeded in making a good inline solder connection between two wires, it’s time for the easy part. Choose some heat-shrink tubing that is just big enough to slide over the joint with a little bit of room to spa...

  • Page 126

    Getting Somewhat More Serious111Experiment 12: Joining Two Wires TogetherI suggest you next practice your soldering skills on a couple of practical proj-ects. In the first one, you can add color-coded, solid-core wires to your AC adapter, and in the second one, you can shorten the power cord for ...

  • Page 127

    Experiment 12: Joining Two Wires TogetherChapter 3112After searching exhaustively I couldn’t find any laptop power cables shorter than 3 feet, so I decided to shorten one myself. If you feel no need to do this, you should try the following procedure on an old extension cord, just as an exercise...

  • Page 128

    Getting Somewhat More Serious113Experiment 12: Joining Two Wires Together5. Use your helping hand to align the first joint. Push the two pieces of wire together so that the strands intermingle, and then squeeze them tight between finger and thumb, so that there are no little bits sticking out. A ...

  • Page 129

    Experiment 13: Broil an LEDChapter 3114Experiment 13: Broil an LEDIn 16,Chapter 1, you saw how an LED can be damaged if too much current flows through it. The electricity caused heat, which melted the LED. Unsurprisingly, you can just as easily melt it by applying too much heat to one of its lea...

  • Page 130

    Getting Somewhat More Serious115Experiment 13: Broil an LEDThrow away your burned-out LED. Substitute a new one, connected as before, but add a full-size copper alligator clip to one of the leads up near the body of the LED, as shown in Figure 3-68. Press the tip of your 30-watt or 40-watt sol-de...

  • Page 131

    Experiment 13: Broil an LEDChapter 3116FundAmentAlsAllaboutperforatedboardFor the remainder of this book, you’ll be using perforated board whenever you want to create permanent, soldered circuits. There are three ways to do this:1. Point-to-point wiring. You use perforated board that has no con...

  • Page 132

    Getting Somewhat More Serious117Experiment 14: A Pulsing GlowExperiment 14: A Pulsing GlowYou will need:• Breadboard• 15-watt pencil-type soldering iron• Thin solder (0.022 inches or similar)• Wire strippers and cutters• Plain perforated board (no copper etching necessary)• Small vise...

  • Page 133

    Experiment 14: A Pulsing GlowChapter 3118Figure 3-75 shows these features. Compare it with Figure 2-103 100,on page 85. R1 is now 33K instead of 470K. R2 and R3 are reduced to 1K. R4 also is 1K, to so that the capacitor takes longer to discharge through it. And C1 is now 100 µF instead of 2.2 ...

  • Page 134

    Getting Somewhat More Serious119Experiment 14: A Pulsing GlowResizingtheCircuitThe first step is to look at the physical components and imagine how to fit them into a small space. Figure 3-78 shows a 3D view of a compact arrangement. Check this carefully, tracing all the paths through the circuit...

  • Page 135

    Experiment 14: A Pulsing GlowChapter 3120When I’m working on this kind of project, I like to place it (with the vise at-tached) on a soft piece of polyurethane foam—the kind of slab that is nor-mally used to make a chair cushion. The foam protects the components from damage when the board is ...

  • Page 136

    Getting Somewhat More Serious121Experiment 14: A Pulsing GlowFlying Wire Segments The jaws of your wire cutters exert a powerful force that peaks and then is suddenly released when they cut through wire. This force can be translated into sudden mo-tion of the snipped wire segment. Some wires are ...

  • Page 137

    Experiment 14: A Pulsing GlowChapter 31221. You can put the battery in a pocket, and mount the flasher on the outside of the pocket, with a thin wire penetrating the fabric. Note that the tiny power connector on the perforated board will accept two 22-gauge wires if they are solid core, or if the...

  • Page 138

    Getting Somewhat More Serious123Experiment 14: A Pulsing GlowBecause the LED will flash at about the speed of a human heart while the per-son is resting, it may look as if it’s measuring your pulse, especially if you mount it on the center of your chest or in a strap around your wrist. If you e...

  • Page 139

    Experiment 14: A Pulsing GlowChapter 3124BAckgroundMaddenedbymeasurementThroughout most of this book, I’ve mostly used measurements in inches, although sometimes I’ve digressed into the metric system, as when referring to “5-mm LEDs.” This isn’t inconsistency on my part; it reflects the...

  • Page 140

    Getting Somewhat More Serious125Experiment 14: A Pulsing GlowFigure 3-83. Because units of measurement are not standardized in electronics, conversion is often necessary. The chart on the right is a 5x magnification of the bottom section of the chart on the left.

  • Page 141

    Experiment 14: A Pulsing GlowChapter 3126Figure 3-84. This chart allows conversion between hundredths of an inch, conventional U. S. fractions of an inch, and fractions expressed in thousandths of an inch.

  • Page 142

    Getting Somewhat More Serious127Experiment 15: Intrusion Alarm RevisitedExperiment 15: Intrusion Alarm RevisitedTime now to add some of the enhancements to the intrusion alarm that I dis-cussed at the end of 97,Experiment 11. I’m going to show you how the alarm can be triggered if you install ...

  • Page 143

    Experiment 15: Intrusion Alarm RevisitedChapter 3128MagneticSensorSwitchesA typical alarm sensor switch consists of two modules: the magnetic mod-ule and the switch module, as shown in Figures 3-85 and 3-86. The magnetic module contains a permanent magnet, and nothing else. The switch module cont...

  • Page 144

    Getting Somewhat More Serious129Experiment 15: Intrusion Alarm RevisitedABreak-to-MakeTransistorCircuitFirst, recall how an NPN transistor works. When the base is not sufficiently posi-tive, the transistor blocks current between its collector and emitter, but when the base is relatively positive,...

  • Page 145

    Experiment 15: Intrusion Alarm RevisitedChapter 3130I have shown the switches open, because that’s the way the schematic for a switch is drawn, but imagine them all closed. The base of the transistor will now be supplied through the long piece of wire connecting all the closed switches, and the...

  • Page 146

    Getting Somewhat More Serious131Experiment 15: Intrusion Alarm RevisitedSelf-LockingRelayThere’s only one remaining problem: we want the alarm to continue making noise even after someone who has opened a door or window closes it again quickly. In other words, when the relay is activated, it mus...

  • Page 147

    Experiment 15: Intrusion Alarm RevisitedChapter 3132Q1R11K10KPower tonoisemaker12VDCSwitchesactivatedby openeddoors orwindowsFigure 3-91. The self-locking relay depicted in has been incorporated in the alarm circuit, so that if any switch in the network is opened, the relay will continue to power...

  • Page 148

    Getting Somewhat More Serious133Experiment 15: Intrusion Alarm Revisitedfrom positive to negative, as shown by its arrow symbol. If current tries to flow in the opposite direction, the diode blocks it. The only price you pay for this service is that the diode imposes a small voltage drop on elect...

  • Page 149

    Experiment 15: Intrusion Alarm RevisitedChapter 3134essentIAlsAllaboutdiodesA diode is a very early type of semiconductor. It allows electricity to flow in one direction, but blocks it in the opposite direction. (A light-emitting diode is a much more recent invention.) Like an LED, a diode can be...

  • Page 150

    Getting Somewhat More Serious135Experiment 15: Intrusion Alarm RevisitedCompletingtheBreadboardAlarmCircuitIt’s time now to breadboard the control circuit for your alarm noisemaker. Fig-ure 3-95 shows how this can be done. I am assuming that you still have the noisemaker, which functions as bef...

  • Page 151

    Experiment 15: Intrusion Alarm RevisitedChapter 3136The breadboarded relay circuit is exactly the same as the schematic in Figure 3-93. The components have just been rearranged and squeezed together so that they will fit alongside the relay. Two wires at the lower-left corner go to the network of...

  • Page 152

    Getting Somewhat More Serious137Experiment 15: Intrusion Alarm RevisitedessentIAlsPerfboardsolderingprocedureCarefully note the position of a component on your bread-board, and then move it to the same relative position on the perfboard, poking its wires through the little holes. Turn the perfboa...

  • Page 153

    Experiment 15: Intrusion Alarm RevisitedChapter 3138toolsFourmostcommonperfboardingerrors1. Too much solderBefore you know it, solder creeps across the board, touches the next copper trace, and sticks to it, as de-picted in Figure 3-101. When this happens, you have to wait for it to cool, and the...

  • Page 154

    Getting Somewhat More Serious139Experiment 15: Intrusion Alarm RevisitedTransferring components from the breadboard to the perforated board should be fairly simple, as long as you don’t try to move too many at once. Follow the suggestions described in previous section “Essentials: Perfboard p...

  • Page 155

    Experiment 15: Intrusion Alarm RevisitedChapter 3140SwitchesandInputsfortheAlarmNow you need to make the system easy to use. The block diagram in Figure 3-105 shows one additional box near the top of the sequence: User Controls. These will consist of switches, LEDs, and connections to the outside...

  • Page 156

    Getting Somewhat More Serious141Experiment 15: Intrusion Alarm RevisitedWhen S1 is in its Off position, it still supplies positive power through its up-per contact to S2, the pushbutton. When the pushbutton is pressed, so that it goes into its “Test” position, the pole of S2 connects with the...

  • Page 157

    Experiment 15: Intrusion Alarm RevisitedChapter 3142InstallingtheSwitchesIf you bought a project box from RadioShack, it may have come with two op-tional top panels: one made of metal, the other made of plastic. I’ll assume that you’ll use the plastic one, as you’ll have more trouble drilli...

  • Page 158

    Getting Somewhat More Serious143Experiment 15: Intrusion Alarm RevisitedThe circuit board will sit on the bottom, held in place with four #4-size ma-chine screws (bolts) with washers and nylon-insert locknuts. You need to use locknuts to eliminate the risk of a nut working loose and falling among...

  • Page 159

    Experiment 15: Intrusion Alarm RevisitedChapter 3144attach them, and don’t allow the iron to remain in contact with anything for more than 10 seconds. It will quickly melt insulation, and may even damage the internal parts of the switches.In projects that are more complex than this one, it woul...

  • Page 160

    Getting Somewhat More Serious145Experiment 15: Intrusion Alarm RevisitedFinalTestWhen you’ve completed the circuit, test it! If you don’t have your network of magnetic sensor switches set up yet, you can just use a piece of wire to con-nect the two binding posts. Make sure that S1 is in its O...

  • Page 161

    Experiment 15: Intrusion Alarm RevisitedChapter 3146Now deal with the power supply. Use your AC adapter, set to 12 volts, hooked up to your type N power plug, or attach the power plug to a 12-volt alarm battery.If you use a battery, be especially careful that the wire leading to the center termin...

  • Page 162

    4147Chips, Ahoy!Before I get into the fascinating topic of integrated circuit (IC) chips, I have to make a confession: some of the things I asked you to do in 110,Chapter 3 could have been done a bit more simply. Does this mean you have been wasting your time? No, I firmly believe that by buildi...

  • Page 163

    Shopping List: Experiments 16 Through 24Chapter 4148FundAmentAlsChoosingchipsFigure 4-2 shows what is often referred to as an integrated circuit (IC). The circuit is actually etched onto a tiny wafer or “chip” of silicon, embedded in a black plastic body, which is properly referred to as the ...

  • Page 164

    Chips, Ahoy!149Shopping List: Experiments 16 Through 24FundAmentAlsChoosingchips(continued)After the letters identifying the generation, you’ll find two (sometimes more) numerals. These identify the specific function of the chip. You can ignore any remaining letters and numerals. Looking back a...

  • Page 165

    Shopping List: Experiments 16 Through 24Chapter 4150Here’s your chip list:• 555 Timer. STMicroelectronics SA555N, Fairchild NE555D, RadioShack TLC555, or similar. Do not get the “CMOS” version of this chip, or any fancy versions such as those of high precision. Buy the cheapest you can fi...

  • Page 166

    Chips, Ahoy!151Shopping List: Experiments 16 Through 24Latching relaysYou’re going to need a 5-volt latching relay that has two coils, instead of one. The first coil flips the relay one way; the second coil flips it back. The relay consumes no additional power while remaining passively in each ...

  • Page 167

    Shopping List: Experiments 16 Through 24Chapter 4152Figure 4-10. When shopping for a numeric keypad, it should have 12 keys in “touch-tone phone” layout, and should have at least 13 contacts for input/output. The contacts are visible here along the front edge. Figure 4-11. This keypad has in...

  • Page 168

    Chips, Ahoy!153Experiment 16: Emitting a PulseExperiment 16: Emitting a PulseI’m going to introduce you to the most successful chip ever made: the 555 timer. As you can find numerous guides to it online, you might question the need to discuss it here, but I have three reasons for doing so:1. It...

  • Page 169

    Experiment 16: Emitting a PulseChapter 4154Insert the chip in your breadboard so that its pins straddle the channel down the center. Now you can easily feed voltages to the pins on either side, and read signals out of them. See Figure 4-14 for a precise guide to placement, in the first project. T...

  • Page 170

    Chips, Ahoy!155Experiment 16: Emitting a PulseSet your power supply to deliver 9 volts. It will be convenient for this experiment if you supply positive down the righthand side and negative down the lefthand side of the breadboard, as suggested in Figure 4-14. C3 is a large capacitor, at least 10...

  • Page 171

    Experiment 16: Emitting a PulseChapter 4156The graphs in Figure 4-17 illustrate what is happening. The upper graph shows the voltage applied to pin 2 by random button-presses, with the potentiometer turned to various values. The lower graph shows that the 555 is triggered if, and only if, the vol...

  • Page 172

    Chips, Ahoy!157Experiment 16: Emitting a Pulse0v3v6v9v0v3v6v9vpulse width remainsfixed at 5.2 secondsPressing and releasing the button for varying intervalswhile adjusting the voltage with the potentiometerOutputVoltagePin 3TriggerVoltagePin 2Figure 4-17. The top graph shows voltage on the trigge...

  • Page 173

    Experiment 16: Emitting a PulseChapter 4158theoryInsidethe555timer:monostablemodeThe plastic body of the 555 timer contains a wafer of silicon on which are etched dozens of transistor junctions in a pattern that is far too complex to be explained here. However, I can summarize their function by d...

  • Page 174

    Chips, Ahoy!159Experiment 16: Emitting a PulsetheoryInsidethe555timer:monostablemode(continued)The green rectangle, identified as “FF,” is a “flip-flop.” I have depicted it as a DPDT switch, because that’s how it functions here, although of course it is really solid-state. Initially whe...

  • Page 175

    Experiment 16: Emitting a PulseChapter 4160BAckgroundHowthetimerwasbornBack in 1970, when barely a half-dozen corporate seedlings had taken root in the fertile ground of Silicon Valley, a company named Signetics bought an idea from an engineer named Hans Camenzind. It wasn’t a huge breakthrough...

  • Page 176

    Chips, Ahoy!161Experiment 16: Emitting a PulseFundAmentAlsWhythe555isusefulIn its monostable mode (which is what you just saw), the 555 will emit a single pulse of fixed (but programmable) length. Can you imagine some applications? Think in terms of the pulse from the 555 controlling some other c...

  • Page 177

    Experiment 17: Set Your ToneChapter 4162Experiment 17: Set Your ToneI’m going to show you two other ways in which the 555 timer can be used. You will need the same items as 168,in Experiment 16, plus:• Additional 555 timer chip. Quantity: 1.• Miniature loudspeaker. Quantity: 1.• 100K lin...

  • Page 178

    Chips, Ahoy!163Experiment 17: Set Your ToneFigure 4-21. These components should be added on the same breadboard below the components shown in Figure 4-14. Use the following values to test the 555 timer in its astable mode: R1: 1K R2: 10K R3: 100Ω C1: 0.047 µF ceramic or electrolytic C2: 0....

  • Page 179

    Experiment 17: Set Your ToneChapter 4164theoryInsidethe555timer:astablemodeHere’s what is happening now, illustrated in Figure 4-23. Initially, the flip-flop grounds C1 as before. But now the low voltage on the capacitor is connected from pin 7 to pin 2 through an external wire. The low voltage...

  • Page 180

    Chips, Ahoy!165Experiment 17: Set Your TonetheoryInsidethe555timer:astablemode(continued)R1 now controls the charge time on its own, while R2 controls the discharge time. The formula for calculating the frequency is now:Frequency = 1440 / ((R1 + R2) × C1)If you set R1 = R2, you should get almost...

  • Page 181

    Experiment 17: Set Your ToneChapter 4166FundAmentAlsThe following table shows 555 timer frequency in astable mode:• Frequency is in pulses per second, rounded to two figures. • The horizontal scale shows common resistor values for R2. • The vertical scale shows common capacitor values for C...

  • Page 182

    Chips, Ahoy!167Experiment 17: Set Your ToneA primary advantage of using pin 5 to adjust frequency is that you can control it remotely. Take the output from pin 3 of another 555 timer running slowly in astable mode, and pipe it through a 2K2 resistor to pin 5. Now you get a two-tone siren effect, ...

  • Page 183

    Experiment 17: Set Your ToneChapter 4168You can also use the output from one chip to trigger another (i.e., you can con-nect pin 3 from the first chip to pin 2 of the second). When the output from the first chip is low, it’s less than half a volt. This is well below the threshold that the secon...

  • Page 184

    Chips, Ahoy!169Experiment 17: Set Your Tone• Halve the value of R5 while doubling the value of C4, so that the cycle time of IC1 stays about the same, but the On time becomes significantly longer than the Off time. • Change the supply voltage in the circuit from 9 volts to 6 volts or 12 volts...

  • Page 185

    Experiment 18: Reaction TimerChapter 4170Experiment 18: Reaction TimerBecause the 555 can easily run at thousands of cycles per second, we can use it to measure human reactions. You can compete with friends to see who has the fastest response—and note how your response changes depending on your...

  • Page 186

    Chips, Ahoy!171Experiment 18: Reaction TimerCheck Figure 4-33 showing the Kingbright display, and you’ll see I have an-notated each pin with its function. You can step down the display with the positive wire from your power supply, making sure that each pin lights an ap-propriate segment.Incide...

  • Page 187

    Experiment 18: Reaction TimerChapter 4172Grounding YourselfTo avoid the frustration that occurs when you power up a circuit and nothing happens, be sure to take these precautions when you use the older generation of CMOS chips (which often have part numbers from 4000 upward, such as 4002, 4020, a...

  • Page 188

    Chips, Ahoy!173Experiment 18: Reaction TimerFundAmentAlsCountersandseven-segmentdisplaysMost counters accept a stream of pulses and distribute them to a series of pins in sequence. The 4026 decade counter is unusual in that it applies power to its output pins in a pattern that is just right to il...

  • Page 189

    Experiment 18: Reaction TimerChapter 4174something magical about seeing a display count from 000 through 999 “all by itself,” and I chose this project because it also has a lot of instructional value.S1 is attached to the “clock disable” pin of IC1, so that when you hold down this button,...

  • Page 190

    Chips, Ahoy!175Experiment 18: Reaction TimerPulseGenerationA 555 timer is ideal for driving a counter chip. You’ve already seen how to wire a 555 to create a stream of pulses that made noise through a loudspeaker. I’m reproducing the same circuit in Figure 4-38 in simplified form, using the p...

  • Page 191

    Experiment 18: Reaction TimerChapter 4176RefinementsNow it’s time to remember that what we really want this circuit to do is test a person’s reflexes. When the user starts it, we want an initial delay, followed by a signal—probably an LED that comes on. The user responds to the signal by pr...

  • Page 192

    Chips, Ahoy!177Experiment 18: Reaction TimerIn bistable mode, the 555 has turned into one big flip-flop. To avoid any un-certainty, we keep pins 2 and 4 normally positive via pull-up resistors, but negative pulses on those pins can overwhelm them when we want to flip the 555 into its opposite sta...

  • Page 193

    Experiment 18: Reaction TimerChapter 4178TheDelaySuppose we set up yet another 555 in monostable mode. Trigger its pin 2 with a negative pulse, and the timer delivers a positive output that lasts for, say, 4 seconds. At the end of that time, its output goes back to being negative. Maybe we can ho...

  • Page 194

    Chips, Ahoy!179Experiment 18: Reaction Timer8. Low voltage on pin 2 of IC1 allows IC1 to start counting.9. User presses S3, the “stop” button.10. S3 connects pin 2 of IC6 to ground.11. IC6 output flips to high and flops there.12. High output from IC6 turns off the LED.13. High output from IC6...

  • Page 195

    Experiment 18: Reaction TimerChapter 4180First remove the 1 µF capacitor at C2 and substitute a 10 µF capacitor. Because you are multiplying the capacitance by 10, you will reduce the speed by 10. The leftmost digit in your display should now count in seconds, reaching 9 and rolling over to 0 e...

  • Page 196

    Chips, Ahoy!181Experiment 19: Learning LogicSummingUpThis project demonstrated how a counter chip can be controlled, how counter chips can be chained together, and three different functions for 555 timers. It also showed you how chips can communicate with each other, and introduced you to the bus...

  • Page 197

    Experiment 19: Learning LogicChapter 418210K10K1K74HC00NANDgateLM78050.33uF0.1uF9v DCFigure 4-46. By observing the LED when you press either, both, or neither of the buttons, you can easily figure out the logical function of the NAND gate.When you connect power, the LED should light up. Press one...

  • Page 198

    Chips, Ahoy!183Experiment 19: Learning LogicThe 74HC00 actually contains four NAND gates, each with two logical inputs and one output. They are arrayed as shown in Figure 4-49. Because only one gate was needed for the simple test, the input pins of the unused gates were shorted to the negative si...

  • Page 199

    Experiment 19: Learning LogicChapter 4184BAckgroundFromBooletoShannonGeorge Boole was a British mathematician, born in 1815, who did something that few people are ever lucky enough or smart enough to do: he invented an entirely new branch of mathematics.Interestingly, it was not based on numbers....

  • Page 200

    Chips, Ahoy!185Experiment 19: Learning LogicBAckgroundFromBooletoShannon(continued)Ann iswearingthe hatBob iswearingthe hatThiscombinationcan beYESYESYESNONONOYESNOTRUETRUEFALSETRUEFigure 4-52. The hat-wearing possibilities can be expressed in a “truth table.”Input A Input B OutputONONONOFFOF...

  • Page 201

    Experiment 19: Learning LogicChapter 4186essentIAlsLogicgatebasicsThe NAND gate is the most fundamental building block of digital computers, because (for reasons which I don’t have space to explain here) it enables digital addition. If you want to explore more try searching online for topics su...

  • Page 202

    Chips, Ahoy!187Experiment 19: Learning LogicessentIAlsLogicgatebasics(continued)If you have difficulty visualizing logic gates, a mechanical comparison may help. You can think of them as being like sliding plates with holes in them, in a bubblegum machine. Two people, A and B, can push the plates...

  • Page 203

    Experiment 19: Learning LogicChapter 4188essentIAlsLogicgatebasics(continued)BABORAAABBNONO NOYESNO YESYESNOYESYESYES YESINPUT AINPUT BOUTPUTFigure 4-60NORAAAABBBBYESNO NONONO YESNONOYESNOYES YESINPUT AINPUT BOUTPUTFigure 4-61

  • Page 204

    Chips, Ahoy!189Experiment 19: Learning LogicessentIAlsLogicgatebasics(continued)BABAXORAABBNONO NOYESNO YESYESNOYESNOYES YESINPUT AINPUT BOUTPUTFigure 4-62ABABXNORBBAAYESNO NONONO YESNONOYESYESYES YESINPUT AINPUT BOUTPUTFigure 4-63

  • Page 205

    Experiment 19: Learning LogicChapter 4190BAckgroundTheconfusingworldofTTLandCMOSBack in the 1960s, the first logic gates were built with Transistor-Transistor Logic, abbreviated TTL, meaning that tiny bipolar transistors were etched into a single wafer of silicon. Soon, these were followed by Com...

  • Page 206

    Chips, Ahoy!191Experiment 19: Learning LogicBAckgroundTheconfusingworldofTTLandCMOS(continued)CMOS family:40xx The old original generation, now obsolete. 40xxB The 4000B series was improved but still susceptible to damage from static electricity. Many hobby circuits still use these chips because...

  • Page 207

    Experiment 19: Learning LogicChapter 4192BAckgroundTheconfusingworldofTTLandCMOS(continued)Bottom line: I suggest you use the 4000B chips only if you want to replicate an old circuit, or if a modern equivalent is unavailable (which is why I specified the 4026B chip for the reaction timer—I coul...

  • Page 208

    Chips, Ahoy!193Experiment 19: Learning LogicFundAmentAlsCommonpartnumbersEach 14-pin chip can contain four 2-input gates, three 3-input gates, two 4-input gates, one 8-input gate, or six single-input inverters, as shown in the following table.2 input3 input4 input8 inputAND 740874117421NAND 74007...

  • Page 209

    Experiment 19: Learning LogicChapter 4194FundAmentAlsRulesforconnectinglogicgatesPermitted:• You can connect the input of a gate directly to your regulated power supply, either positive side or nega-tive side.• You can connect the output from one gate directly to the input of another gate.•...

  • Page 210

    Chips, Ahoy!195Experiment 19: Learning LogicFundAmentAlsRulesforconnectinglogicgates(continued)Not permitted:• No floating-input pins! On CMOS chips such as the HC family, you must always connect all input pins with a known voltage, even if they supply a gate on the chip that you’re not using...

  • Page 211

    Experiment 19: Learning LogicChapter 4196In the 74HCxx logic family, each input of a logic gate consumes just a micro-amp, while the output can source 4 milliamps. This seems paradoxical: how can the chip give out more than it takes in? The answer is that it also consumes power from the power sup...

  • Page 212

    Chips, Ahoy!197Experiment 20: A Powerful CombinationExperiment 20: A Powerful CombinationSuppose you want to prevent other people from using your computer. I can think of two ways to do this: using software, or using hardware. The software would be some kind of startup program that intercepts the...

  • Page 213

    Experiment 20: A Powerful CombinationChapter 4198• Latching relay, 5 volt, DPST or DPDT, “2 form C” package, Panasonic DS2E-SL2-DC5V or similar. Must have two separate coils (one to latch, one to unlatch) with separate inputs. Quantity: 1.• LEDs, 5mm generic, your choice of colors. Quanti...

  • Page 214

    Chips, Ahoy!199Experiment 20: A Powerful CombinationI want this to be a battery-powered circuit, so that you don’t have to run a separate power supply to it or (worse) try to tap into your computer’s 5-volt bus. Battery power means that the circuit has to be “off” most of the time, to pre...

  • Page 215

    Experiment 20: A Powerful CombinationChapter 4200IncorrectInputsWhat happens if you enter the wrong code? If you press any button other than 1, 4, or 7, it sends positive voltage to the inverter near the top of the sche-matic. The positive voltage overwhelms the negative voltage being applied to ...

  • Page 216

    Chips, Ahoy!201Experiment 20: A Powerful CombinationTo help it make sense, I’ve shown the logic gates that exist inside the chips. I’ve also colored the power supply wires, as before, to reduce the risk of confusion. The positive side of the supply goes only to the common terminal on your key...

  • Page 217

    Experiment 20: A Powerful CombinationChapter 4202OneLittleDetail:TheComputerInterfaceOld computers used to have a big switch at the back, attached to the heavy metal box inside the computer, that transformed house current to regulated voltages that the computer needs. Most modern computers are no...

  • Page 218

    Chips, Ahoy!203Experiment 20: A Powerful CombinationPower Upbutton oncomputerSolderjointsHeat-shrink tubing(not yet shrunk)To yourlatchingrelayConnectorComputer motherboardFigure 4-85. The combination lock project can be interfaced with a typical desktop com-puter by cutting one conductor in the ...

  • Page 219

    Experiment 20: A Powerful CombinationChapter 4204Another enhancement could be an additional 555 timer that is activated by the asterisk button, and delivers power to the other chips for, say, a limited period of 30 seconds, allowing you that much time to unlock the system. This would eliminate th...

  • Page 220

    Chips, Ahoy!205Experiment 21: Race to PlaceExperiment 21: Race to PlaceThe next project is going to get us deeper into the concept of feedback, where the output is piped back to affect the input—in this case, blocking it. It’s a small project, but quite subtle, and the concepts will be useful...

  • Page 221

    Experiment 21: Race to PlaceChapter 4206Also, there’s another problem. After a player lets his finger off the button, the other players’ buttons will be unblocked again. I need a latch to hold the signal from the first player’s button and continue to block the other players.ButtonBlockerBut...

  • Page 222

    Chips, Ahoy!207Experiment 21: Race to PlaceButtonBlockerLatchButtonBlockerLatchButtonBlockerLatchFigure 4-89. If a latch is added below each button, it can retain one input and then block all inputs from all buttons. This simplifies the concept.ButtonBlockerLatchResetPlayButtonBlockerLatchFigure ...

  • Page 223

    Experiment 21: Race to PlaceChapter 4208So now, finally, here’s a simplified schematic, in Figure 4-92. I like to show the pins of the 555 timers in their correct positions, so I had to move the compo-nents around a little to minimize wire crossovers, but you can see that logi-cally, it’s the...

  • Page 224

    Chips, Ahoy!209Experiment 21: Race to PlaceThe only way to change IC1 is if the quizmaster flips his switch back to the left. That applies negative power to the reset pins of both the timers. Consequently their outputs go low, the LED goes out, and the circuit goes back into the same state as whe...

  • Page 225

    Experiment 21: Race to PlaceChapter 4210185551855574HC325V DC regulated10K10KOR2OR3OR110KS2S3S13300.010.01330Figure 4-95. Applying the simplified schematic to a breadboard inevitably entails a wiring layout that is less intuitively obvious and appears more complex. The connections are the same, t...

  • Page 226

    Chips, Ahoy!211Experiment 22: Flipping and BouncingExperiment 22: Flipping and BouncingI mentioned in the previous experiment that “bounce” from the buttons in the circuit wouldn’t be a problem, because the buttons were activating 555 tim-ers that were wired in bistable, flip-flop mode. As ...

  • Page 227

    Experiment 22: Flipping and BouncingChapter 4212HowItWorksTwo NOR gates or two NAND gates can function as a flip-flop: • Use NOR gates when you have a positive input from a double-throw switch.• Use NAND gates when you have a negative input from a double-throw switch.Either way, you have to u...

  • Page 228

    Chips, Ahoy!213Experiment 22: Flipping and Bouncingof the left NOR gate goes from positive to negative, as a result of the pull-down resistor. But the righthand input of this gate is still positive, and one positive is all it takes to make the NOR maintain its negative output, so nothing changes....

  • Page 229

    Experiment 23: Nice DiceChapter 4214Experiment 23: Nice DiceThis is the one experiment where I want you to use the 74LSxx generation of the TTL logic family, instead of the 74HCxx family of CMOS. Two reasons: first, I need to use the 7492 counter, which is unavailable in the HC family. And sec-on...

  • Page 230

    Chips, Ahoy!215Experiment 23: Nice DiceNo connectionNo connectionNo connectionNegativeto enableNegativeto enableNo connectionClockinput ABinaryoutput ABinaryoutput BClockinput BBinaryoutput CBinaryoutput D74LS92Counter1234567141312111098Figure 4-101. The unusual pin assignments include four that ...

  • Page 231

    Experiment 23: Nice DiceChapter 4216Now we come to the first new and difficult fact about the 74LSxx generation of TTL chips that makes them less desirable, for our purposes, than the 74HCxx generation of CMOS chips that I have recommended in previous projects. The modern and civilized HC chips w...

  • Page 232

    Chips, Ahoy!217Experiment 23: Nice Dicedisplay for a finished version of the dice circuit, I’ll deal with that later. Accord-ing to my meter, the 4K7 resistor holds the current between 0.3mA and 0.4mA, which is the counter’s rated maximum.Set up your initial version of the circuit as shown in...

  • Page 233

    Experiment 23: Nice DiceChapter 4218Getting back to our project: I want to take the three binary outputs and make them create patterns like the spots on a die. How can I do this? Quite easily, as it turns out. I’m assuming that I’ll use seven LEDs to simulate the patterns of spots on a die. T...

  • Page 234

    Chips, Ahoy!219Experiment 23: Nice DiceEach of the LEDs is grounded through a separate 4K7 load resistor. Unfortu-nately, this means that when they are displaying the pattern for a 6, all of them are running in parallel from the output of the NOR gate, which overloads it. As long as you don’t l...

  • Page 235

    Experiment 23: Nice DiceChapter 4220Note that to maximize this effect, the button has to be held down for a full second or more, so that the 68 µF capacitor becomes fully charged before the button is released.So, this circuit now fulfills the original goal. But can it be better? Of course it can...

  • Page 236

    Chips, Ahoy!221Experiment 23: Nice Dice1K1K1K0.01uF0.1uFD1D2D3D45V DC regulated power supply1855574LS9274LS2774LS06Eachresistorbelowis 120ohms10K10K68uFFigure 4-111. If open-collector inverters are added to the dice schematic, it can drive full-size LEDs with up to 40mA, as long as the LEDs are t...

  • Page 237

    Experiment 23: Nice DiceChapter 4222The final enhancements are up to you. Most obviously, you can add a second die, as many games require two dice. The 74LS27 chip still has a couple of spare NOR gates in it, one of which you can make use of, but you will need an additional 555 timer, running at ...

  • Page 238

    Chips, Ahoy!223Experiment 24: Intrusion Alarm CompletedExperiment 24: Intrusion Alarm CompletedNow let me suggest how you can apply the knowledge from this chapter of the book to upgrade the burglar alarm project that was last modified in 142,Ex- 142,periment 15. You’ll probably need to check ...

  • Page 239

    Experiment 24: Intrusion Alarm CompletedChapter 4224These modifications are so simple that I think the block diagram in Figure 4-114 should be all you need. I don’t think I need to give you any schematics. The only change you have to make to the existing alarm is to substitute the latching rela...

  • Page 240

    Chips, Ahoy!225Experiment 24: Intrusion Alarm CompletedUpgrade3:DelayBeforeDeactivationTypically, alarms include another delay feature. When you open a door on your way into the building and it triggers the alarm, you have 30 seconds to deacti-vate it, before it starts making a noise.How can we i...

  • Page 241

    Experiment 24: Intrusion Alarm CompletedChapter 4226Q1D1R11K10K68uF10K1M10uFPower tonoisemaker12VDCSwitchesactivatedby openeddoors orwindows555Figure 4-115. This addition to the original alarm circuit imposes a one-minute delay before the alarm sounds. The 555 timer (wired in bistable mode) recei...

  • Page 242

    5227What Next?At this point, we can branch out in numerous directions. Here are some possibilities:Audio electronicsThis is a field in itself, including hobby projects, such as simple amplifiers and “stomp boxes,” to modify guitar sound.Radio-frequency devicesAnything that receives or transmi...

  • Page 243

    Shopping List: Experiments 25 Through 36Chapter 5228Shopping List: Experiments 25 Through 36ToolsYou won’t need any new tools for this section of the book.SuppliesandComponentsAs we have progressed to the point where you may want to pick and choose which projects you attempt, I will list the su...

  • Page 244

    What Next?229Customizing Your Work AreaThis leads me to two conclusions: 1. You need storage above the workbench.2. You need storage below the workbench.Many DIY workbench projects allow little or no storage underneath. Or, they suggest open shelves, which will be vulnerable to dust. My minimum c...

  • Page 245

    Customizing Your Work AreaChapter 5230For undivided, flat-format storage boxes, the Prolatch 23600-00 is ideally sized to fit a file-cabinet drawer, and the latches are sufficiently secure that you could stack a series of them on their long edges. See Figure 5-4.Plano also sells some really nicel...

  • Page 246

    What Next?231Customizing Your Work AreaLabelingNo matter which way you choose to store your parts, labeling them is essential. Any ink-jet printer will produce neat-looking labels, and if you use peelable (nonpermanent) labels, you’ll be able to reorganize your parts in the future, as always se...

  • Page 247

    Customizing Your Work AreaChapter 5232The surface of your desk or workbench will undoubtedly become scarred by ran-dom scuffs, cut marks, and drops of molten solder. I use a piece of half-inch ply-wood, two feet square, to protect my primary work area, and I clamp a miniature vise to its edge. To...

  • Page 248

    What Next?233Reference SourcesReference SourcesOnlineMy favorite educational and reference site is Doctronics actionURI(http://www.doctronics.co.uk):(http://www.doctronics.actionURI(http://www.doctronics.co.uk):co.uk). I like the way they draw their schematics, and I like the way they include man...

  • Page 249

    Reference SourcesChapter 5234BooksYes, you do need books. As you’re already reading this one, I won’t recommend other beginners’ guides. Instead, in keeping with the orientation of this chap-ter, I’ll suggest some titles that will take you farther in various directions, and can be used fo...

  • Page 250

    What Next?235Reference SourcesThe Encyclopedia of Electronic Circuits, by Rudolf F. Graf (Tab Books, 1985)A totally miscellaneous collection of schematics, with minimal explana-tions. This is a useful book to have around if you have an idea and want to see how someone else approached the problem....

  • Page 251

    Experiment 25: MagnetismChapter 5236Experiment 25: MagnetismThis experiment should be a part of any school science class, but even if you remember doing it, I suggest that you do it again, because setting it up takes only a matter of moments, and it’s going to be our entry point to a whole new ...

  • Page 252

    What Next?237Experiment 25: MagnetismtheoryInductanceWhen electricity flows through a wire, it creates a magnetic field around the wire. Because the electricity “induces” this effect, it is known as inductance. The effect is illustrated in Figure 5-13.Figure 5-13. When the flow of electricity...

  • Page 253

    Experiment 25: MagnetismChapter 5238BAckgroundJosephHenryBorn in 1797, Joseph Henry was the first to develop and demonstrate powerful electromagnets. He also originated the concept of “self-inductance,” meaning the “electrical inertia” that is a property of a coil of wire.Henry started ou...

  • Page 254

    What Next?239Experiment 26: Tabletop Power GenerationExperiment 26: Tabletop Power GenerationIf you have just three components, you can see magnetism generating elec-tricity right in front of you, right now. You will need:• Cylindrical neodymium magnet, 3/4-inch diameter, axially magnetized. Qu...

  • Page 255

    Experiment 26: Tabletop Power GenerationChapter 5240Figure 5-20. Three neodymium magnets, 1/4-, 1/2-, and 3/4-inch in diameter. I would have preferred to photograph them standing half-an-inch apart, but they refused to permit it.Figure 5-21. By moving a magnet vigor-ously up and down through the ...

  • Page 256

    What Next?241Experiment 26: Tabletop Power GenerationFigure 5-22. Because inductance increases with the diameter of a coil and with the square of the number of turns, your power output from moving a magnet through the coil can increase dramatically with scale. Those wishing to live “off the gri...

  • Page 257

    Experiment 27: Loudspeaker DestructionChapter 5242Experiment 27: Loudspeaker DestructionI’d like you to sacrifice a 2-inch loudspeaker, even though it means wasting the $5 or so that it probably costs. Actually, I don’t consider this a waste, because if you want to learn how a component works...

  • Page 258

    What Next?243Experiment 27: Loudspeaker DestructionBAckgroundOriginsofloudspeakersLoudspeakers utilize the fact that if you run a varying electrical current through a coil situated in a magnetic field, the coil will move in response to the current. This idea was introduced in 1874 by Ernst Siemen...

  • Page 259

    Experiment 27: Loudspeaker DestructionChapter 5244theorySound,electricity,andsoundTime now to establish a clear idea of how sound is transformed into electricity and back into sound again.Suppose someone bangs a gong with a stick. The flat metal face of the gong vibrates in and out, creating soun...

  • Page 260

    What Next?245Experiment 27: Loudspeaker DestructiontheorySound,electricity,andsound(continued)Somewhere along the way, we may want to record the sound and then replay it. But the principle remains the same. The hard part is designing the micro-phone, the amplifier, and the loudspeaker so that the...

  • Page 261

    Experiment 28: Making a Coil ReactChapter 5246Experiment 28: Making a Coil ReactA capacitor will absorb some DC current until it is fully charged, at which point it blocks the flow. There’s another phenomenon that I haven’t mentioned so far, which is the exact opposite of capacitance. It’s ...

  • Page 262

    What Next?247Experiment 28: Making a Coil React12VDCFigure 5-34. The breadboarded version of the schematic in Figure 5-33 shows a simple way to set it up for a quick demo. The green button is a tactile switch. The two red LEDs should be placed so that the polarity of one is opposite to the polari...

  • Page 263

    Experiment 28: Making a Coil ReactChapter 5248Here’s one last variation on this experiment to test your understanding of elec-trical fundamentals. Remove the 220Ω resistor, and substitute a 1K resistor (to protect your LED from sustained current). Remove the coil, and substitute a very large c...

  • Page 264

    What Next?249Experiment 29: Filtering Frequencies Experiment 29: Filtering Frequencies In this experiment, you’ll see how self-inductance and capacitance can be used to filter audio frequencies. You’re going to build a crossover network: a simple circuit that sends low frequencies to one plac...

  • Page 265

    Experiment 29: Filtering Frequencies Chapter 5250ProcedureThe purpose of the audio amplifier chip is to provide enough power to get a decent amount of sound out of your loudspeaker. The purpose of using a 5-inch speaker is to enable you to hear lower-frequency sounds than the baby speakers that w...

  • Page 266

    What Next?251Experiment 29: Filtering Frequencies 0.15uF0.15uF0.22uF10K33K100uFNP8 ohms10uF NP100ft hookupwire on spool100uF100uFNP100uF100uF123413141516567891011129VDC100uFTEA2025BInput fromheadphone jackon audio deviceFigure 5-41. The audio amplifier chip should be wired with capacitors around ...

  • Page 267

    Experiment 29: Filtering Frequencies Chapter 5252The 33K resistor is necessary to protect the amplifier from being overdriven. If you don’t get enough volume using your music player, decrease the 33K value. If the music is too loud and distorted, increase the value. You can also try omit-ting o...

  • Page 268

    What Next?253Experiment 29: Filtering Frequencies CrossoverNetworksIn a traditional audio system, each speaker cabinet contains two drivers—one of them a small speaker called a tweeter, which reproduces high frequencies, the other a large speaker known as a woofer, which reproduces low frequen-...

  • Page 269

    Experiment 29: Filtering Frequencies Chapter 5254So here’s the specification for this particular coil in an audio crossover network. Forty feet of 20-gauge copper magnet wire, wrapped in 200 turns around a spool of 1/16–inch-thick plastic with a hub measuring 7/8 inch in length be-tween the f...

  • Page 270

    What Next?255Experiment 29: Filtering Frequencies theoryWaveformsIf you blow across the top of a bottle, the mellow sound that you hear is caused by the air vibrating inside the bottle, and if you could see the pressure waves, they would have a distinctive profile. If you could slow down time and...

  • Page 271

    Experiment 29: Filtering Frequencies Chapter 5256theoryWaveforms(continued)You can create your own waveform as an input for your au-dio amplifier with the basic astable 555 timer circuit shown in Figure 5-51. You have to be careful, though, not to over-load the amplifier input. Note the 680K seri...

  • Page 272

    What Next?257Experiment 30: FuzzExperiment 30: FuzzLet’s try one more variation on the circuit in 261,Experiment 28. This will demon-strate another fundamental audio attribute: distortion.You will need:• One more 100K potentiometer.• Generic NPN transistors: 2N2222 or similar. Quantity: 2....

  • Page 273

    Experiment 30: FuzzChapter 5258SchematicThe output from the 555 timer is a square wave, so it already sounds quite “fuzzy,” but we can make it more intense to demonstrate the clipping princi-ple. I’ve redrawn the whole circuit in Figure 5-55, as several components have changed. The principa...

  • Page 274

    What Next?259Experiment 30: Fuzz0.15uF1uF1K0.15uF0.22uF820100uFNP8 ohms100uF100uFNP100uF100uF123413141516567891011129VDC100uFTEA2025B12345678555timer1K100K100K33K3908K20.01uF0.1uF0.01uF0.1uFAudio Signalinput pointFigure 5-55. For a quick demo of clipping, insert a couple of transistors between th...

  • Page 275

    Experiment 30: FuzzChapter 5260BAckgroundStomp-boxoriginsThe Ventures recorded the first single to use a fuzz box, titled “The 2,000 Pound Bee,” in 1962. Truly one of the most awful instrumentals ever made, it used distortion merely as a gimmick and must have discouraged other musicians from ...

  • Page 276

    What Next?261Experiment 30: FuzzBAckgroundStomp-boxorigins(continued)Harry DeArmond sold the first tremolo box, which he named the Trem-Trol. It looked like an antique portable radio, with two dials on the front and a carrying handle on top. Perhaps in an effort to cut costs, DeArmond didn’t us...

  • Page 277

    Experiment 31: One Radio, No Solder, No PowerChapter 5262Experiment 31: One Radio, No Solder, No PowerTime now to go back one more time to inductance and capacitance, and dem-onstrate an application which also makes use of the way that waveforms can be added to each other. I want to show you ho...

  • Page 278

    What Next?263Experiment 31: One Radio, No Solder, No Power wire. Use your two thumb nails to pull the insulation apart, revealing about a half-inch of bare wire, as shown in Figure 5-61. Bend it at the center point and twist it into a loop, as shown in Figure 5-62. You just made a “tap,” mean...

  • Page 279

    Experiment 31: One Radio, No Solder, No Power Chapter 5264earphone. A normal modern earphone or headphone will not work in this circuit. The return wire from the headphone is connected to a jumper wire, the other end of which can be clipped to any of the taps in your coil.One last modification, a...

  • Page 280

    What Next?265Experiment 31: One Radio, No Solder, No Power Figures 5-66 and 5-67 show the completed radio.If you’ve managed to follow these instructions (one way or another), it’s time to tune your radio to the nearest station. Move the alligator clip at the end of your patch cord from one ta...

  • Page 281

    Experiment 31: One Radio, No Solder, No Power Chapter 5266theoryHowradioworksWhen electrical frequencies are very high, the radiation they create has enough energy to travel for miles. This is the principle of radio transmission: A high-frequency voltage is applied to a broadcasting antenna, rela...

  • Page 282

    What Next?267Experiment 31: One Radio, No Solder, No Power theoryHowradioworks(continued)Figure 5-71. An antenna at the top of the schematic picks up faint electromagnetic radiation from a distant transmitter. The coil at the left side is tapped at intervals so that its resonance can be adjusted ...

  • Page 283

    Experiment 32: A Little Robot CartChapter 5268Experiment 32: A Little Robot CartRobotics is another application of electronics that deserves a book in itself—or several books. So, once again, I’m going to give you an introduction fol-lowed by some points that you can follow if you want to go ...

  • Page 284

    What Next?269Experiment 32: A Little Robot Cartplywood to complete the two little robotics projects here (ideally, the kind of thin, high-quality plywood sold by hobby stores) but I recommend something that looks better and is easier to work with: ABS plastic. Before you start on the robotic cart...

  • Page 285

    Experiment 32: A Little Robot CartChapter 5270Cut with Care You can saw ABS, but if you use a table saw, the plastic will tend to melt and stick to the blade. These smears will get warm and sticky when you feed the next piece of plastic into the saw, and the result will be extremely unpleasant. T...

  • Page 286

    What Next?271Experiment 32: A Little Robot CartCurvingCutsCurving cuts involve relatively little danger, although eye protection and gloves are still advisable. My preferred tools:• Band saw with a 3/8- or 1/4-inch blade designed for thin wood or plywood. • Jigsaw. I have a special liking for...

  • Page 287

    Experiment 32: A Little Robot CartChapter 5272MakingPlansI like to use drawing software to create plans, and I try to print them at actual scale. I tape them to the smooth side of a piece of white or natural-color ABS, then use an awl to prick through the plan into the soft surface beneath. I re-...

  • Page 288

    What Next?273Experiment 32: A Little Robot CartYou can work with it for about half a minute, and when you have it the way you want it, spray or sponge water onto it to make it set quickly. Alternatively, if you need more time, you can reheat it. The amount of force necessary to bend the sheet inc...

  • Page 289

    Experiment 32: A Little Robot CartChapter 5274Figure 5-88Figure 5-89. Figures 5-86 through 5-89 illustrate four steps to join two pieces of ABS using #4 sheet-metal screws. Cut 7/64-inch holes on a line 1/8 inch from the edge of the first piece, then mark through the holes to the edge of the seco...

  • Page 290

    What Next?275Experiment 32: A Little Robot Cart23"3"3"3"8"9"5"2"1/2"2 1/2"2 1/2"1/2"1/4"2"3"4"2"Drill half-inchholes to makerounded insidecornersBendBendMakefourwheelsABCDEFFigure 5-92. These sections of 1/4-inch...

  • Page 291

    Experiment 32: A Little Robot CartChapter 52765-94 and 5-95 will help to make this clear. Initially, when you install Part F, use only two screws, one each side, so that you can adjust its angle a little. This will be necessary to optimize the contact of the wheels with the floor.The side wheels ...

  • Page 292

    What Next?277Experiment 32: A Little Robot Cart0.01uF47uF100K50K10KMotor12345678Figure 5-98. This ultrasimple schematic is all the cart needs to enable it to back up when it hits an obstacle.The motor I chose requires 5 volts, so I had to use a voltage regulator with a 9-volt battery. If your mot...

  • Page 293

    Experiment 32: A Little Robot CartChapter 5278FundAmentAlsAllaboutlimitswitchesThe most obvious enhancement for your cart would be a better steering mechanism. You could use another motor to take care of this, with a pair of limit switches. Because limit switches are a basic, important idea in co...

  • Page 294

    What Next?279Experiment 32: A Little Robot CartFundAmentAlsAllaboutlimitswitches(continued)Figure 5-99. The three diagrams, from top to bottom, show three snapshots of a motor controlled by a DPDT relay and two limit switches. When the on/off switch at bottom-right sends power to the relay, the l...

  • Page 295

    Experiment 32: A Little Robot CartChapter 5280FundAmentAlsAllaboutmotorsBrushed DC motorThis is the oldest, simplest design for an electric motor, shown in very simplified form in Figure 5-101. Coils are attached to a shaft where they can interact with sta-tionary magnets around them. The magneti...

  • Page 296

    What Next?281Experiment 32: A Little Robot CartTake-home messages from this experiment include the following:• You can buy simple DC motors with reduction gearing built in, providing your choice of RPM. Literally hundreds of websites will sell you small mo-tors for robotics projects.• When yo...

  • Page 297

    Experiment 32: A Little Robot CartChapter 5282FundAmentAlsWiregaugesIf you’re going to power larger motors, or other components that take more current than LEDs or small relays, you really need to know about wire gauges. In particular, what’s the relationship between wire thickness and AWG (A...

  • Page 298

    What Next?283Experiment 32: A Little Robot CarttheoryCalculatingvoltagedropAnother fact that you often need to know is how much of a voltage drop a particular length of wire will introduce in a circuit. If you want to get maximum power from a motor, you don’t want to lose too much voltage in th...

  • Page 299

    Experiment 33: Moving in StepsChapter 5284theoryCalculatingvoltagedrop(continued)This table shows the percent voltage lost in a circuit with 10-foot wire at 12 volts.Wire GaugeAmperes12345678910100.080.170.250.330.420.500.580.670.750.83120.130.270.400.530.660.800.931.11.21.3140.210.420.630.841.11...

  • Page 300

    What Next?285Experiment 33: Moving in Steps• ULN2001A or ULN2003A Darlington arrays by STMicroelectronics. Quantity: 2.• CMOS octal or decade counter. Quantity: 2.• Various resistors and capacitors.ExploringYourMotorI’ve specified a unipolar, four-phase, 12-volt motor because this is a ve...

  • Page 301

    Experiment 33: Moving in StepsChapter 5286The coil inside the motor is holding the shaft in position, and the power that the motor draws will be dissipated as heat. It’s quite normal for the motor to get warm while you’re using it. The trouble is, if you use a battery to power it, and you for...

  • Page 302

    What Next?287Experiment 33: Moving in StepsI’ve used a 10K resistor to pull up the input to each 555, so that the timers are naturally in their quiescent state. A 0.01 μF capacitor links the output from one timer to the input of the next so that they are electrically isolated from each other, ...

  • Page 303

    Experiment 33: Moving in StepsChapter 5288theoryInsideasteppermotorIf you check the Wikipedia entry for stepper motors, you may see a very nice 3D rendering showing a toothed rotor and four coils arrayed around it. Maybe stepper motors used to be manufactured like this once upon a time, but not a...

  • Page 304

    What Next?289Experiment 33: Moving in StepstheoryInsideasteppermotor(continued)In reality, the magnets are not separate from each other. The edge of a rotor is magnetized in zones that alternate between south and north polarity. And instead of multiple coils, there are just four windings that go ...

  • Page 305

    Experiment 33: Moving in StepsChapter 5290SpeedControlIf you are a truly exceptionally observant, you may have noticed that I left pin 5 of each of the timers unconnected in the schematic for driving the stepper motor in Figure 5-108. Normally, pin 5 should be grounded through a capacitor to prev...

  • Page 306

    What Next?291Experiment 33: Moving in StepsInitially I suggested a step time of 1/4 second just so that you could see what was happening. When you’re actually using this circuit, you’ll never need it to run as slowly as that. So you can increase the entire range of speeds. Remove the 22 μF ...

  • Page 307

    Experiment 33: Moving in StepsChapter 5292the chip functions as an inverter, so that when the input goes high, the output goes low and sinks current. This is of course just what we need for our stepper motor that has a common positive connection.The ULN2001A is only an amplification device, so yo...

  • Page 308

    What Next?293Experiment 34: Hardware Meets SoftwareExperiment 34: Hardware Meets SoftwareThroughout this book, in accordance with the goal of learning by discovery, I have asked you to do an experiment first, after which I’ve suggested the gen-eral principles and ideas that we can learn from it...

  • Page 309

    Experiment 34: Hardware Meets SoftwareChapter 5294There are three answers:1. MCUs cannot do everything. They need other components to help them interact with the world, such as transistors, relays, sensors, and amplifiers. You need to know how those things work, so that you can make intel-ligent ...

  • Page 310

    What Next?295Experiment 34: Hardware Meets SoftwareSuppliesFigure 5-122 shows some of the chips in the PICAXE range. I’ll be telling you how to use the smallest—the 08M—which costs less than $5 and is cheaper than any other MCU that I’ve found. It has only 256 bytes of memory to store a p...

  • Page 311

    Experiment 34: Hardware Meets SoftwareChapter 5296You can use the PICAXE with a serial cable, but I don’t recommend it. The old RS-232 serial communications standard on PCs is pretty much obsolete, and PICAXE has recognized this by offering a USB cable (which contains a serial converter inside ...

  • Page 312

    What Next?297Experiment 34: Hardware Meets SoftwareScroll down past all the software until you get to Additional Resources. Look for the AXE027 PICAXE USB Download Cable. At first glance, it looks as if they want to sell you a cable, but in fact this is the list of drivers. Double-click the one a...

  • Page 313

    Experiment 34: Hardware Meets SoftwareChapter 5298In the Programming Editor, go to View→Options and click the Mode tab, then click the button to select the 08M chip.Figure 5-127. This screenshot shows the options win-dow of the PICAXE Program Editor, which you must use to select the type of chi...

  • Page 314

    What Next?299Experiment 34: Hardware Meets Software33010K12345678PICAXE08Mcba22KFigure 5-131. The schematic of a test circuit for the PICAXE 08M shows the underside of the stereo socket, the essential 10K and 22K resistors on the input pin, and an LED to show an output from the chip.Be aware that...

  • Page 315

    Experiment 34: Hardware Meets SoftwareChapter 5300In fromComputerOut toComputer NegativePowerFigure 5-132. Correct wiring of the socket is essential. When soldering wires to the lower terminals, make sure that you attach the wires to both of the terminals in each pair.Figure 5-133. The breadbo...

  • Page 316

    What Next?301Experiment 34: Hardware Meets SoftwareIf you detect the voltage, the software is installed and working properly. In that case, there’s a problem on your breadboard, either in the chip or in the wiring around it. If you cannot detect any voltage, the software probably wasn’t insta...

  • Page 317

    Experiment 34: Hardware Meets SoftwareChapter 5302DecodingtheCodeLet’s take a look at the little program that you typed in. The first line identifies a section of the program. This program only has one section, and we’re calling it “main.” Any word with a colon after it is the name of a s...

  • Page 318

    What Next?303Experiment 34: Hardware Meets SoftwareEditingWhat if you want to change the program? No problem! Use the Programming Editor to change one of the lines in the program. Substitute 100 instead of 1000 milliseconds, for instance. (The pause command can be followed by any number up to 655...

  • Page 319

    Experiment 34: Hardware Meets SoftwareChapter 5304LoopsHere’s another thing I’d like you to try. Rewrite your program code as shown here and download it onto the PICAXE: main: for b0 = 1 to 5 high 1 pause 200 low 1 pause 200 next ...

  • Page 320

    What Next?305Experiment 34: Hardware Meets SoftwareFundAmentAlsBasicPICAXEparametersHere are some of the most useful parameters of the PICAXE:• The PICAXE requires 5 volts DC, regulated. • The inputs and outputs of the PICAXE are compatible with 5-volt logic chips. You can attach them directl...

  • Page 321

    Experiment 35: Checking the Real WorldChapter 5306Experiment 35: Checking the Real WorldOften we want a microcontroller to measure something and respond in an appropriate way. For instance, it can measure a low temperature and sound an alarm, as I suggested in the example that I gave earlier.The ...

  • Page 322

    What Next?307Experiment 35: Checking the Real WorldNow we need a program to tell the chip what to do. Using the Programming Editor, start a new document. The code should look like this: main: readadc 2,b0 debug b0 goto mainThe command “readadc 2,b0” means “read the a...

  • Page 323

    Experiment 35: Checking the Real WorldChapter 5308This table shows measurements made with PICAXE 08M controller. Resistance (in ohms) between the ADC pin and the negative supplyEquivalent digital value200025519002431800230170021816002051500192140017913001661200154110014110001289001158001027009060...

  • Page 324

    What Next?309Experiment 35: Checking the Real WorldNotice what’s happening here. First we get a value in b0, and then on the next line, we do some arithmetic with it. The asterisk means “multiply.” So the state-ment says, “Take whatever value is in b0, multiply by 5, and transfer it to an...

  • Page 325

    Experiment 35: Checking the Real WorldChapter 5310FundAmentAlsExtrafeaturesA complete guide to the 08M would fill a book of its own, and of course such books already exist (just search the books section of Amazon.com for keyword “picaxe”). But I’ll finish my introduction to the controller b...

  • Page 326

    What Next?311Experiment 36: The Lock, RevisitedExperiment 36: The Lock, RevisitedThe combination lock that I described in 212,Experiment 212, 20 is especially appro-priate for a microcontroller, because it requires a series of operations that resemble a computer program. I’m going to show how ...

  • Page 327

    Experiment 36: The Lock, RevisitedChapter 5312say that the value will be between 71 and 83. If we specify a range as shown in the following table, we have a much better chance of interpreting each button correctly.Button numberRange960071–83670084–96380097–1080900109–12181000122–1345110...

  • Page 328

    What Next?313Experiment 36: The Lock, Revisitedb0 receives the value supplied by the analog-digital converter when it looks at the keypad. After storing the number in b0, the routine has to figure out which keypad key it matches. The key identity (0 through 9) will be stored in another variable, ...

  • Page 329

    Experiment 36: The Lock, RevisitedChapter 5314I have chosen an arbitrary combination of 7-4-1 for our combination lock. Us-ing these numbers, the main section of the program looks like this:main: low 1 gosub getkey if b1<>7 then main gosub getkey if b1<>4 then main g...

  • Page 330

    What Next?315Experiment 36: The Lock, RevisitedFigure 5-148. This screenshot shows the complete listing of a program to read a sequence of three keypresses in conjunction with a combination lock. If the sequence is correct, the PICAXE sends a high output from one of its pins. If the sequence is i...

  • Page 331

    Experiment 36: The Lock, RevisitedChapter 5316FundAmentAls UnexploredterritoryIf you’ve taken the time to complete most of the projects in this book with your own hands, you have gained a very rapid introduction to the most fundamental areas of electronics. What have you missed along the way? H...

  • Page 332

    What Next?317In ClosingOtherControllersIf you want something more powerful, a BASIC Stamp is the logical next step after a PICAXE. the BASIC Stamp is so called because it originally looked like a postage stamp. The BASIC Stamp has a larger vocabulary of commands and a bigger range of add-on devic...

  • Page 333

  • Page 334

    A319Online Retail Sources and ManufacturersThis appendix contains URLs for companies mentioned as retail sources or manufacturers, along with the commonly used name of the source and the company name.Colloquially used nameActual corporate or company nameURL3MMinnesota Mining and Manufacturing Co....

  • Page 335

    Appendix320Colloquially used nameActual corporate or company nameURLDeWaltDeWalt Industrial Tool CompanyactionURI(http://www.dewalt.com):http://www.dewalt.comDigi-KeyDigi-Key CorporationactionURI(http://www.digikey.com):http://www.digikey.comDirected switchesDirected Electronics Inc.actionURI(ht...

  • Page 336

    Online Retail Sources and Manufacturers321 Colloquially used nameActual corporate or company nameURLPanaVisePanavise Products, Inc.http://www.panavise.comParallaxParallax, Inc.http://www.parallax.comPep BoysPep Boys-Manny, Moe and Jackhttp://www.pepboys.comPhilipsKoninklijke Philips Electronics N...

  • Page 337

  • Page 338

    AcknowledgmentsMy association with MAKE magazine began when its editor, Mark Frauenfelder, asked me to write for it. I have always been very grateful to Mark for his sup-port of my work. Through him I became acquainted with the exceptionally capable and motivated production staff at MAKE. Gareth ...

  • Page 339

  • Page 340

    325 IndexNumbers2N2222 transistor, 2,73(see also Experiments 11 and 15)2N6027 programmable unijunction transistor (see Experiment 14: A Pulsing Glow) 2,3M, 319breadboard 2,, 39single inline sockets and headers, 2,1039-volt battery 2,, 512-key numeric keypad, 2,15140xxB chip, 2,19140xx chip 2,...

  • Page 341

    Index326alligator clips, 2,4copper 2,, 101All Spectrum Electronics 2,, 319LEDs 2,, 4Alpha potentiometers 2,, 4, 319ALPS pushbutt 2,on, 319alternating current, 2,12, 248Amaz 2,on, 319deburring tool, 2,99electronic solder, 2,100GB Automatic Wire Strippers 2,, 40pick and hook set 2,, 99amperage...

  • Page 342

    Index327 74HC32 (see Experiment 21: Race to Place)74LS06 open-collector inverter chip 2,, 15074LS27 (see Experiment 23: Nice Dice)74LS27 triple-input NOR chip 2,, 15074LS92 counter chip, 2,15074LS92 (see Experiment 23: Nice Dice)555 timer (see 555 timer chip)4026, 2,150(see also Experiment 18:...

  • Page 343

    Index328Experiment 6: Very Simple Switching, 2,43–54connection problems 2,, 45schematics, 2,50–54testing 2,, 45–49tools 2,, 44–45Experiment 7: Relay-Driven LEDs, 2,55–59AC adapter plugs 2,, 55–56how it works 2,, 59operating current, 2,58procedure 2,, 59Experiment 8: A Relay Oscil...

  • Page 344

    Index329 Experiment 33: Moving in Steps, 2,284–292adding autonomy 2,, 291exploring your motor 2,, 285–286quick demo 2,, 286–289setting up light seeking robot, 2,291–292speed control 2,, 290–291Experiment 34: Hardware Meets Software, 2,293–305decoding the code 2,, 302editing code 2...

  • Page 345

    Index330insulated binding posts, 2,103insulator 2,, 6integrated circuit chips (see chips)intrusion alarm (see Experiments 11, 15, and 24)Jjacks, 2,49Jameco, 2,320potentiometer 2,, 42solder, 2,100joules 2,, 36jumper wire assortment, 2,41KKellogg, Edward 2,, 243keypads(see Experiment 20: A Po...

  • Page 346

    Index331 Newark ElectronicsVectorboard 2,, 101newtons 2,, 36NKK switches 2,, 320noisemaking circuit, 2,92nonpolarized electrolytic capacitors, 2,249nonpolarized relays 2,, 58NOR gates 2,, 212Noyce, Robert 2,, 152NPN and PNP transistors, 2,76–77, 79, 2,258numeric keypads(see Experiment 20: ...

  • Page 347

    Index332reactance 2,, 246reference sources 2,, 233–235books, 2,234–235online 2,, 233relay-driven LEDs (see Experiment 7: Relay-Driven LEDs)relay oscillator (see Experiment 8: A Relay Oscillator)relays, 2,42, 56–58coil voltage, 2,58inside, 2,58latching 2,, 151nonpolarized, 2,58self-loc...

  • Page 348

    Index333 Ttactile switches, 2,151tamper-proof screws 2,, 203tantalum capacitor, 2,63Texas Instruments, 2,3214026 Decade Counter 2,, 150logic chips 2,, 150TheoryAlternating current concepts, 2,248Basic measurements 2,, 36Binary arithmetic, 2,217Calculating voltage drop, 2,283–284Doing the...

  • Page 349

    Index334wire strippers, 2,40wire wrap, 2,106woofer 2,, 253work area, customizing 2,, 228–232 2,bench, 231computer 2,, 232labeling 2,, 231oscilloscope 2,, 231XX-Acto, 2,321miniature hand saw, 2,99Xcelite 2,, 321pliers, 2,1Xytronic, 2,321soldering iron, 2,96ZZener diode, 2,134zinc electr...

  • Page 350

    ColophonThe heading and cover font are BentonSans, the text font is Myriad Pro, and the code font is TheSansMonoCondensed.About the AuthorCharles Platt became interested in computers when he acquired an Ohio Scientific C4P in 1979. After writing and selling software by mail order, he taught class...

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