Lesson 27 Understanding the NAND Gate Oscillator

Chapter Lesson 27 Understanding the NAND Gate Oscillator

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

  • Lesson 27Understanding the NANDGate OscillatorTable L27-1 describes the present system. It is aneven closer look at how the NAND gate works.The NAND gate oscillator is widely used becauseit can be tuned easily using an RC. Watch for thenew vocabulary. Master the material now or be aslave later.Recall the logic table for the NAND gate (Table L27-2).In review, recall what happens at RC1. Gate 1 is used to start the RC1. RC1’s C1 fills and drainsthrough R2. These control the time the circuit stays on.■Gate 1 output goes high.■D1 traps the voltage on RC1 side.■C1 fills.■R2 drains the voltage.The action of an RC circuit is always the same.The only difference is the speed that the circuitfills or drains. Figure L27-1 reviews that basicaction.But we are interested now in RC2. RC2 is madeof C2 and R4. They use gate 2 to make anoscillator. The oscillation action happens at gate 2.Look at the setup of gate 2 shown in FigureL27-2. The high or low state of pin 3 determinesLesson 27 ■Understanding the NAND Gate Oscillator 103InputProcessorsOutputPush RC1-Push on/LED flashing once buttontimed off about per second10 per secondRC2-NAND gate RCM oscillatorAt 1 flash per secondTABLE L27-1The System Diagram as It Exists NowInput AInput B Output(Pin 2)(Pin 1)(Pin 3)HighHighLowHighLowHighLowHighHighLowLowHighTABLE L27-2Logic Table for the NAND GateFigure L27-1Figure L27-2