555 timer problem

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xterminator
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Joined: Fri Apr 11, 2003 2:51 pm

555 timer problem

Post by xterminator »

I want to create a 'pulse' output when a switch is set to 'OFF'
The pulse may only occur when the switch is gooing from ON to OFF, while the switch is set to on, nothing may happen

Below is a time-graph of what I'm trying to accomplish (Vcc is rated @ 12 VDC):
Image

Anybody help ?

Note: I'm new @ this so pls keep it simple :)

Tnx in advance
Guest

Post by Guest »

If you use a simple RC differentiator and a diode, you can pick up the falling edge of the switch. With some combinations of inverters with the aforementioned circuit, you will be able to trigger 555 and generate a 1 second pulse.
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