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TOUCH_OPERATED_CODE_PRACTICE_OSCILLATOR

2016-08-31 04:04  
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TOUCH_OPERATED_CODE_PRACTICE_OSCILLATOR
A touch-operated CPO is shown in the figure. The gates of IC1-a are biased high through the two 22-MΩ resistors (R1 and R2), keeping its output low. Gates IC1-b and IC1-c are connected in an audio oscillator circuit that can operate only when pin 5 of IC1-b is high. The last gate of the 4093, IC1-d, adds isolation to the oscillator's circuit and drives the speaker (SPKR1). Touching the key paddle and ground plane lowers IC1-a's input gate voltage to near zero, allowing the output at pin 3 to go high. The tone generator then turns on and sends out an audio note. The touch key paddle and ground plane can be made from a circuit board or any other conductible material. Note that the ground plane should lie flat for a hand rest and the key paddle should be positioned for ease of touch.