NEGATIVE_TRIGGERED_TOUCH_CIRCUIT

Published:2009/7/8 3:32:00 Author:May | From:SeekIC

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 multi ibrator's on time is determined by the values of R1 and C1. Although R1 is shown to be a 100-K unit, its value can be anything between 10 K and 1 MΩ . 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. If the value of R4 is reduced to a much lower value, such as 10 KΩ , the circuit can be triggered with a negative pulse through 0.1-μF capacitor connected to pin 6. With a 100-K Ω resistor for R1, and a 4.7-μF electrolytic capacitor for C1, the circuit's on time is about 0.6 second. When R1 is increased to 470 K Ω, the on time of the circuit is increased to over 6 seconds.



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