Re: Timer circuit help
From: Rich Webb (bbew.ar_at_mapson.nozirev.ten)
Date: 11/20/04
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Date: Sat, 20 Nov 2004 04:11:34 GMT
On 19 Nov 2004 18:02:59 -0800, sprintracer@gmail.com (Robo) wrote:
>Looking for a circuit that when the input goes high (+12) the output
>will pulse 3 to 4 times with a 50% duty cycle at approx. 6 Hz, and
>then remain high as long as the input stays high.
>Is it possible to do this with a 555 timer? If so looking for some
>help with the circuit, or some other possible simple circuit solution.
>
>Input:
> ____________________________
>_____| |___........
>
>Output:
> _ _ ____________________
>_____| |_| |_| |___........
>
> ^ 3-4 pulses 50% duty cycle ~6 Hz
>
>
>Any help/direction would be greatly appreciated. Thanks...
Off the top of my head... You could use a 555 for part of the circuit,
running off of the +12 as an astable at 6 Hz. Next to that, use a
voltage divider to 5 V and a cap with a time constant of half a second
or so. Take the output pulse train from the 555 (through another voltage
divider down to 5 V) and the top of the capacitor each to the inputs of
an OR gate.
You'll probably want a diode in parallel with the top of the voltage
divider that drives the cap, so that it dumps quickly when the driving
pulse goes away. Schmitt-trigger inputs on the OR gate.
I'm sure there's a simpler way, but it's getting late...
-- Rich Webb Norfolk, VA
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