Lesson 20 Test Point 2—The NAND Gate Processor at Work

Chapter Lesson 20 Test Point 2—The NAND Gate Processor at Work

Electronic Circuits for the Evil Genius Second Edition 64 Lessons with Projects
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Electronic Circuits for the Evil Genius Second Edition 64 Lessons with Projects

  • state. Is that voltage greater than half of thepower source voltage?___________It should read 0.0 volts. With the plungerdown, it should be connected directly toground.Describe the state of the inputs to thefirst NAND gate when the push button isclosed.Describe what happens to the voltage onthe DMM when you release the push button.The other instrument reading shown in FiguresL19-4 and L19-5 is an oscilloscope. Eachhorizontal line equals 2 volts. The line representingvoltage is at 4.5 lines up. 4.5 3 2 represents 9 volts.Don’t worry if you don’t have a properoscilloscope available. Your computer can be usedas a cheap “scope” with freeware available online.Soundcard Scope was developed by ProffessorChristain Zeitnitz.It is a wonderful tool and available atactionURI(www.zeitnitz.de/christian/scope_en):www.zeitnitz.de/christian/scope_en. The onlyfailing is that it is limited to measuring rapidlychanging signals. We’ll be doing that soon enough.It will not measure a stable DC input.Lesson 20Test Point 2—The NAND Gate Processor at WorkWhen the inputs are connected to ground, the outputwill be internally connected to voltage. Try it out! For the NAND gate, if the inputs are connectedto voltage, the output should be connected toground. Conversely, if the inputs are connected tovoltage, the output is internally connected toground. The results happen instantly. Take aminute and understand the NAND gate.What to ExpectWith the system at rest and the push buttonuntouched, measure the voltage at the output of the first NAND gate at pin 11 (Table L20-1).Lesson 20 ■Test Point 2—The NAND Gate Processor at Work 81Figure L19-3Figure L19-4Figure L19-5Input AInput BOutputHighHighLowHighLowHighLowHighHighLowLowHighTABLE L20-1NAND Gate Logic Table