BOUNCE_FREE_AUTO_REPEAT_SWITCH

Published:2009/7/10 21:17:00 Author:May | From:SeekIC

This switch that keeps pulsing as long as it is pressed is often required. The circuit here used the well known Type 555 for this purpose. Its output is a TTL-compatible signal. Pin 5 of the timer has a potential of 67% of the supply voltage, UCC In the quiescent condition (switch not pressed), C1 charges via R2 and R3 to a voltage that is lower than that at pin 5, and thus is also lower than the toggle voltage.When the switch is pressed, C1 is rapidly charged via R1 to the toggle voltage, upon which the timer emits a pulse. At the same time, the capacitor is discharged again via R4. As long as the switch is pressed, the circuit functions as an astable toggle and produces pulses. When it is released, the capacitor cannot charge to the toggle voltage.



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