Negative-triggered-touch-circuit

  
The 4047 is configured as a monostable multivibrator circuit or one shot that is set up to trigger on a negative-transition of the signal applied to its pin 6 input. The multivibrator`s on time is determined by the values of R1 and Cl. Although R1 is shown to be a 100-K unit, its value can be anything between 10 K and 1 MO. Capacitor C1 can be a nonpolarized capacitor with any practical value above 100 pF. By making R4`s value extremely high, the circuit can be used as a touch-triggered one-shot multivibrator.
Negative-triggered-touch-circuit - schematic

Ifthe value of R4 is reduced to a much lower-value, such as 10 KO, the circuit can be triggered with a negative pulse through 0.11-" F capacitor connected to pin 6. With a 100-KO resistor for R1, and a 4. 7-flF electrolytic capacitor for C1, the circuit"s on time is about 0.6 second. When R1 is increased to 4 70 KO, the on time of the circuit is increased to over 6 seconds.




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