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Momentary to Pulse Relay


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davelloyd 
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Posted: May 07, 2017 at 6:42 AM / IP Logged Link to Post Post Reply Quote davelloyd
Hi,
My first post here and I know nothing about electronics and wondered if I could get a little advice?
I wired up a relay following this diagram and it works fine.
https://www.the12volt.com/relays/relaydiagram20.html
However, is it possible to make the capacitor discharge more quickly so that the relay becomes operable in a shorter space of time?
Is it simply a matter of using a lower value resistor than the 10k one in the diagram and if so how low of a value can that be? I would like a recovery time of about 1 second rather the the 10 seconds it is taking now.
Any help would be very much appreciated.
Thanks
Dave
the12volt 
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Posted: May 08, 2017 at 8:07 AM / IP Logged Link to Post Post Reply Quote the12volt
Use a smaller capacitor for a shorter output duration using the constant to momentary diagram you linked to in your post, however it sounds like you're using a larger capacitor than the one shown.
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davelloyd 
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Posted: May 08, 2017 at 1:15 PM / IP Logged Link to Post Post Reply Quote davelloyd
Thanks for the advice.
I am using a 1k uf capacitor and a 1k ohm resistor as per the diagram and the output time is about 1/2 second and that is just fine.
Holding the input switch down for any length of time, gives a constant 12v supply and produces the same 1/2 second pulse which is just what I need.
However, the input switch may be pressed for different lengths of time and may need pressing again after a couple of seconds but I am finding that it takes about 10 secs for the capacitor to bleed it's charge down to ground through the resistor and it's that time that I am trying to shorten.
My thoughts were that if I used a smaller resister, say 5k ohms, would the capacitor discharge more quickly without causing a direct short circuit?
Dave
the12volt 
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Posted: May 08, 2017 at 6:00 PM / IP Logged Link to Post Post Reply Quote the12volt
Think less resistance rather than smaller. 5K is more resistance than 1K. You can try a 500 ohm resistor with the 1K micro farad capacitor, but I would suggest using a smaller capacitor instead. Both will give you a shorter output than the 1/2 second output you have now.
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davelloyd 
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Posted: May 09, 2017 at 12:13 AM / IP Logged Link to Post Post Reply Quote davelloyd
Ok.
I made a mistake in my previous post I am using a 10k ohm resistor and not 1k as posted.
The output time of 1/2 second is just fine and I don't want to change that.
After the 12 volt input is removed it takes about 10 secs for the capacitor to bleed it's charge down. If I re-apply the input within that 10 seconds the relay does not operate.
It's the 10 seconds "recovery" time I want to shorten so that I can re-apply the input within, say 2 seconds.
Thanks
Dave
the12volt 
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Posted: May 09, 2017 at 8:21 AM / IP Logged Link to Post Post Reply Quote the12volt
No problem. In that case, try a 5K resistor and please post your results.
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davelloyd 
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Posted: May 09, 2017 at 2:11 PM / IP Logged Link to Post Post Reply Quote davelloyd
Thanks for the help.
I ordered a few resistors of different values so hopefully I'll be able to try it over the weekend if they show up in time.
I will, certainly, let you know the results.
Dave
davelloyd 
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Posted: May 13, 2017 at 12:35 PM / IP Logged Link to Post Post Reply Quote davelloyd
I fitted a 5K ohm resistor.
The pulse time of 1/2 second stayed the same.
The capacitor discharged in about 7 seconds rather than the 12-15 seconds previously.
thanks for the help.
Dave
lulanord 
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Posted: June 23, 2017 at 12:55 PM / IP Logged Link to Post Post Reply Quote lulanord
Hi...i am a new user here. I think 5K is more resistance than 1K. You can try a 500 ohm resistor with the 1K micro farad capacitor, but I would suggest using a smaller capacitor instead. Both will give you a shorter output than the 1/2 second output you have now.

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