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rc timer circuit help

Hi
I have a GSM controller that can switch a relay for a minimum time of 1 sec, however I need a 300ms pulse. I am looking for a circuit that can take the 1 sec relay output (as an input) and give me a 300ms output for a second relay.
Thanks for any help.
 
J

Jon Kirwan

Jan 1, 1970
0
I have a GSM controller that can switch a relay for a
minimum time of 1 sec, however I need a 300ms pulse. I am
looking for a circuit that can take the 1 sec relay output
(as an input) and give me a 300ms output for a second relay.
Thanks for any help.

Does the 300ms start at the beginning of the 1s output
duration or at the end of it? In any case, have you looked at
the 74121 (various families), 74HC221, or 74HC123 to use
together with an external BJT or MOSFET switch?

Jon
 
J

Jasen Betts

Jan 1, 1970
0
Hi
I have a GSM controller that can switch a relay for a minimum time of 1 sec, however I need a 300ms pulse.

how precise do you need to be?
 
Hi

I have a GSM controller that can switch a relay for a minimum time of 1 sec, however I need a 300ms pulse. I am looking for a circuit that can take the 1 sec relay output (as an input) and give me a 300ms output for a second relay.

Thanks for any help.

Hi

Does not need to be that precise but should be below 500ms.
 
Hi

I have a GSM controller that can switch a relay for a minimum time of 1 sec, however I need a 300ms pulse. I am looking for a circuit that can take the 1 sec relay output (as an input) and give me a 300ms output for a second relay.

Thanks for any help.

The out put is a dry contact relay.
 
W

whit3rd

Jan 1, 1970
0
I have a GSM controller that can switch a relay for a minimum time of 1 sec, however I need a 300ms pulse. I am looking for a circuit that can take the 1 sec relay output (as an input) and give me a 300ms output for a second relay.

If this were a system with DC power supply, and logic-level output, it's easy. If it's
an AC-power (mains) system, things get trickier: the best might be an AC timed relay
connected in series, that turns OFF after 300 msec, and resets when power is
removed.

It matters a lot what kind of power is available (and what the nature of the intended
load is).
 
Hi

I have a GSM controller that can switch a relay for a minimum time of 1 sec, however I need a 300ms pulse. I am looking for a circuit that can take the 1 sec relay output (as an input) and give me a 300ms output for a second relay.

Thanks for any help.

Thanks all, going with the capacitor, resistor suggested by John, simple and effective.
 
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