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Figure 1. Switch Debouncing Circuit Diagram Using the 555 Timer
This is a switch debouncing circuit that employs a 555 timer IC. One problem with any pushbutton switch is the oscillation that occurs when it makes electrical contact to close the circuit.  This can result in 'bounces' or undesired multiple pulses that can lead to errors in digital circuits.

   
The circuit above can be used to 'debounce' a pushbutton switch.  It gets its initial trigger from the pushbutton switch and outputs a single clean pulse that the receiving circuit can use error-free.  In this circuit, the 555 timer is essentially configured as a 555 monostable multivibrator.






p rathore
5/15/2013 12:18:46

Nicely explained circuit,a ready made pcb layout-although simple-would have been boon to learner.

Thanks

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gus smith
11/2/2015 02:45:46

Wow, I tried software debouncing and hardware debouncing using a capacitor and resistors and an inverter. But I did not get consistent results using that and RISING edge interrupts on an Arduino. But using a 555 in monostable mode is brilliant and works all the time! I have seen Arduino code where millis() is used and a delay interval. But this one only needs "state = !state" in the interrupt routine to toggle a state. Awesome good old 555!

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