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I'm looking for help with a switch, hopefully I can explain it in a way you can understand.


I want to know if there is a switch that when pressed will make the circuit but when the power goes off will reset to the off position and require pressing again to make the circuit.

Does that make any sense, I hope so.

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Hi Alan,

Thanks for the reply, If operated via a relay the circuit would remain open after a power loss (I think) which means when power returns it would re-activate?

I want the switch to reset so that it can't activate without being pressed again.

Hi Martin,

It is all down to how you wire it and what latching circuits you have.



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Unless one of our intellectual sparky/techy people have any other suggestions you could go down the complicated latching switch circuit, but depending on what your powering could prove expensive if it requires a heavy load?

Or I am pretty sure a push to make switch coupled with a relay would work (assuming we are talking 12v here?) Just feed the load side of the relay contacts back to the +ve side of the relay - this would have the push to make switch between this contact and the +ve rail? Not too good at drawing to show this I'm afraid. When the power fails the contacts will open and thus break the circuit to the relay coil. Push the switch and it resets the contacts until the next power fail.

Or you could use a small electro magnet coupled with a reed switch and a push to make switch to kick it all off. When the power fails the electro magnet fails and thus the reed switch drops open. 

Fit a push to break switch in line with either option in case you want to disable it yourself without dropping the power.

As Alan said, an idea of what you want to do would help?


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Martin - Glad I could help - It might not be the most technically pretty solution, but I always think simple is best. 

That's why I think I am the best - Simples!!! :naughty: LOL

And more impressed you could interpret my ramblings without a diagram!!cheers

Still intrigued to know what the heck your doing though? We are just nosey parkers on here.

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You need a "Low Volts Release Switch"  (NVR) of the appropriate voltage.

Other than that, A double pole change over relay, one pair of N/O ( Normally Open) contacts for the load, the other pair of N/O contacts in parallel with a momentary N/O switch that feeds power to the coil of the relay.

An emergency stop, if required, would be a Normally Closed contact on a momentary switch that kills the supply to the Relay coil.


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