Switching Basics and More

Chapter 2. Switching Basics and More

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

  • 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 without it.Today, switching is mostly done with semiconductors. Before I deal with them, I’ll back up and illustrate the concept by introducing you to relays, which are easier to understand, because you can see what’s going on inside them. And before I get to relays, I’ll deal with everyday on/off switches, which may seem very simple—but we have to nail down the basics.Also in this chapter, I’ll deal with capacitance, because capacitance and resis-tance are fundamental to electronic circuits. By the end of the chapter, you should have a basic grounding in electronics and be able to build the noise-making section of a simple intrusion alarm. This will be your first circuit that does something genuinely useful!Shopping List: Experiments 6 Through 11As in the previous shopping list, you should visit the various online suppliers for availability and pricing of components and devices. Manufacturers seldom sell small numbers of parts directly. Check the appendix for a complete list of URLs for all the companies mentioned here.Devices• Power supply/universal AC adapter, 3 to 12 volts at 1A (1,000 mA). See Fig-ure 2-1. Part number 273-029 from RadioShack, part PH-62092 by Philips, or similar.• Breadboard suitable for integrated circuits. Quantity: 1. See Figures 2-2 and 2-3. Part 276-002 from RadioShack, model 383-X1000 made by PSP, part 923252-I by 3M, or similar. A breadboard that has screw terminals mounted beside it will be a little easier to use but more expensive than one that does not have terminals.Figure 2-1. This AC adapter delivers DC from 3 to 12 volts, and is ideal for electron-ics projects.In thIs chAPter 54,Shopping List: Experiments 54,6 Through 11 58,Experiment 6: Very Simple 58,Switching 67,Experiment 7: Relay-Driven LEDs 72,Experiment 8: A 72, Relay Oscillat 72,or 78,Experiment 9: Time and 78,Capacitors 82,Experiment 10: Transist 82,or Switching 90,Experiment 11: A 90, Modular Project