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Creating one pulse only from a push button (even if kept closed)

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Ja7me

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Hi everyone,

I want to generate ONE pulse only from a push button, even if this push button is kept pushed down.

If the push button is kept pressed down, the length of pulse needs to be below one second. And should only happen once. I do not require a totally clean output signal. Voltage will be about 12V, 4 Amps max

The only way I can think of doing this is with a 555 astable timer (with a transistor to step up output), however the problem with this is that I will get more than one pulse. Is there an easy way to achieve this using just a capacitor and resistor? or some form of analogue timing switch?. Any ideas would be much appreciated.

Kind regards,

Jamie
 
You could use a 555 mono-stable such as the first circuit here. The trigger circuit is capacitively coupled so holding the trigger button down has no effect on the output. If the PB is SPST then you need to connect the PB to ground with a pull-up resistor on the trigger output going to the plus voltage.
 
Hi everyone,

I want to generate ONE pulse only from a push button, even if this push button is kept pushed down.

If the push button is kept pressed down, the length of pulse needs to be below one second. And should only happen once. I do not require a totally clean output signal. Voltage will be about 12V, 4 Amps max

The only way I can think of doing this is with a 555 astable timer (with a transistor to step up output), however the problem with this is that I will get more than one pulse. Is there an easy way to achieve this using just a capacitor and resistor? or some form of analogue timing switch?. Any ideas would be much appreciated.

Kind regards,

Jamie

Take a look at this MC14490 "Hex Bounce Eliminator" (attached). You can configure it to have a continuous output if the button is held down, or to latch the output, or generate a single pulse output (even if the button is held down). You'll have to use it with a drive circuit
though, to handle switching 12V, 4 amps.

It worked well for me..

eT
 

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