Plate Touch Sensor Circuit

Posted on Dec 22, 2012

This system operates on the principle that capacitance loading of an oscillator will lower its frequency. When a foreign body comes into contact with touch plate, the frequency of Ul is lowered.

Plate Touch Sensor Circuit
Click here to download the full size of the above Circuit.

This removes the oscillator signal from Ul from U2`s passband, which causes U2 to lose lock, turns off the LED, and causes the collector of Ql to go low.

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