Hello
I am trying to figure out a circuit that closes a relay for 5 secs when 12volts is applied.
Once the 12v is switched off I need the relay to close for 5 secs once again.

I was thinking of maybe using a capacitor in the circuit to hold the charge for closing the relay once power is removed.

I really need some input on this though.

Thanks in advance


Antony

 

Do you want to learn to build a circuit, or is this a one time thing, where a delay relay would help you out?

It just so happens that this seems the exact operation, I was seeing in another recent thread.

 

Hi
Thank you for your reply.
I have learnt how the 555 timer works and think this will work best for me.
This is the first post I have made, but yes I would like it to be a one shot monostable switch, one pulse when I apply 12v to an accessory wire and then another pulse once that wire has 0v.
There is also a permanent 12v wire the utilize.

Thanks

Antony

 

I hope I haven't discouraged someone from posting a 555 circuit.

For a one time need, I find that the multi-function timer/relays often fit the bill.

Can't compete with a $.25 chip though.

Good luck

 

Did someone say 555? Here's a quick & dirty solution, not tried, not breadboarded but a start. Think it would be better if we used a 2 in quad NOR & eliminate the 2N3904, 1K & 1N4148's, but I'm out of time till monday

 

Hello
I am trying to figure out a circuit that closes a relay for 5 secs when 12volts is applied.
Once the 12v is switched off I need the relay to close for 5 secs once again.

I was thinking of maybe using a capacitor in the circuit to hold the charge for closing the relay once power is removed.

I really need some input on this though.

Thanks in advance


Antony

Is there power available after the 12V is remover?

Ken

 

Hi
Wow thank you for some really good replies, Yes also there will be permanent 12v live supply.

Thanks

Antony

 

A 5 second timer is the trivial part.

The devil lying in the details is a trigger circuit that can fire a timer if the input goes low to high or high to low.

One further spec clarification: If the 12V enable signal changes in under 5 seconds, what happens?

 

Hi
Its basically for my car as I am installing a custom gps system, I need to simulate a push button of the system to power it on/off.

I have been doing some research and have come up with a diagram, see attached.
Basically when the ACC is powered the relay activates one of the monostable switch.
The same then when the ACC is powered down.
I had incorporated a delay in the ACC switching to allow for the starting of the engine which of course disables the ACC for a few seconds.

See what you think? Is there anything I have missed or done wrong?

Thanks

Antony

 

This thread is a violation of the AAC forum rules, Chapter 6, on automotive modifications, as seen here:
http://www.allaboutcircuits.com/l_tos.html
Therefore, this thread will be closed.

Please understand the reasons behind this action and bear no grudge.
Feel free to tread on the rest of the forums.

You may find answers to your questions in one of the links provided here: http://forum.allaboutcircuits.com/showthread.php?t=54400