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Timer for 12v system

Timer for 12v system

Timer for 12v system


I am developing a prototype 12V system comprising a solenoid activated by a PIR sensor. I am looking for a timer device so that the power to the solenoid cuts 1 or 2 seconds after activation.

This is intended as a safety back-up. The PIR sensor should cut out after a minute but that's a bit long and sometimes the power to the solenoid is getting stuck on.

This timer looks suitable : Link (RS Stock No.: 178-5026).

Nb I asked RS directly but they referred me to their 'DesignSpark' forum which is very new I think and doesn't have many users.


RE: Timer for 12v system

That's an on delay relay. You will need to use that to control a second normally closed relay to invert the signal.

Don't forget to buy the socket that goes with that relay.

RE: Timer for 12v system

Or use a contact that is normally open.

RE: Timer for 12v system

I have looked in to this in the past. I recall not being able to find an open delay relay. Only the legacy pneumatic delay relays had double throw contacts. I think the electronic ones are loop powered and need to be on for the timer to work.

RE: Timer for 12v system


This isn't my field and I am a bit confused about the definitions. So bear with me here please.

So what I mean is that the normal situation is that there is no power to the solenoid. Then the PIR sensor detects something and power is switched on. (So I'm not sure if that means it is normally open or normally closed).

Do you think the RS device can be set up to work or should I be looking for something else?

Thanks again

RE: Timer for 12v system

Omron H3CR-A has a 12VDC version and can do all kinds of timing functions.

I'm not sure what you're doing exactly or intended user, building your own circuit might be more suitable. Or try Ebay, lots of small open circuit board stuff available there for 12VDC.

RE: Timer for 12v system

The link above takes me to a Datasheet for a relay with an AC rated contact. This will not be suitable for a DC system. Also note that solenoids are highly inductive, so resistance only rated contacts will also not be suitable.

RE: Timer for 12v system


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