Latching Relay that changes state when power is cycled.

Thread Starter

D. Mac

Joined Mar 28, 2019
7
Looking for a bi-stable relay circuit that changes state whenever power is cycled. 12Vdc, 10 amp load, automotive application. This would be a push-on push-off type of set up but with no "sense" or push button input. Only power & ground. The bi-stable would cycle every time power is applied. No action when power is removed. Or vice-versa.

Thanks for any suggestions or ideas.

Dennis.
 

Thread Starter

D. Mac

Joined Mar 28, 2019
7
Eric, Thanks, These switches provide the action I am looking for, but want a relay to change state & latch whenever power is applied. Dennis.
 

ericgibbs

Joined Jan 29, 2010
9,305
hi Dennis,
OK,
Do you have 12V available to power the latch circuitry or are you considering a latching relay.?
If you used a latching type relay, it would be possible to change the relay state , at power On and Off.
E
 

Thread Starter

D. Mac

Joined Mar 28, 2019
7
E,
No, power is not available to the latch circuit. A latching relay may be the ticket but the circuits that I have seen use a momentary contact push button to cycle the latch. Conceptually I think of a solenoid that actuates a push on - push off switch every time power is applied.
D.
 

mvas

Joined Jun 19, 2017
538
Looking for a bi-stable relay circuit that changes state whenever power is cycled. 12Vdc, 10 amp load, automotive application. This would be a push-on push-off type of set up but with no "sense" or push button input. Only power & ground. The bi-stable would cycle every time power is applied. No action when power is removed. Or vice-versa.

Thanks for any suggestions or ideas.

Dennis.
Push-On / Push-Off Latching Relay
Something like this ...
https://www.ebay.com/itm/DC-6-24V-Latch-Relay-Module-Flip-Flop-Bistable-Self-locking-Trigger-Switch-Board-/282960969172

Find a model that has your exact volt / amps specifications
 

Thread Starter

D. Mac

Joined Mar 28, 2019
7
Thanks for the suggestions, Can these relays be continuously energized? Most seem to be designed to accept a voltage pulse. In this application power would be "On" for an extended time, perhaps hours, then "Off". The latch would be expected to change state when power is "On".
D.
 

ericgibbs

Joined Jan 29, 2010
9,305
hi,
The latching relay will switch over its contacts and remain in that state after the ON pulse has been sent, even if the power is removed.
It requires a release pulse to switch the contacts back their OFF position.
You would need a small circuit to generate the On/Off pulses at Power On and Off.
E
 

kubeek

Joined Sep 20, 2005
5,657
A solenoid and a latching switch might just be the easiest option ;)
With just a relay it does seem to be a bit too complicated. See this picture, but the value of the capacitor will be the biggest problem to get it right and work in all conditions of voltage and temperature. You need just enough energy to latch the relay, but not enough to do it a second time.
 

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AnalogKid

Joined Aug 1, 2013
8,251
It sounds like you want an electromechanical relay that toggles and latches its contacts with each pulse applied to the coil. The contacts are kept in the current state when power is removed, and change to the other state on the next application of power. This can be done with a suitable relay (and a diode across the coil) and nothing else if you don't mind the coil being powered continuously. If you want to save some power and just pulse the coil every time the 12 V comes up, without wiring a small circuit, add a very large capacitor. Does that sound like what you're after?

ak

upload_2019-3-28_11-36-15.png
 

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Last edited:

Tonyr1084

Joined Sep 24, 2015
4,028
It sounds like you want an electromechanical relay that toggles and latches its contacts with each pulse applied to the coil. The contacts are kept in the current state when power is removed, and change to the other state on the next application of power. This can be done with a suitable relay (and a diode across the coil) and nothing else if you don't mind the coil being powered continuously. If you want to save some power and just pulse the coil every time the 12 V comes up, without wiring a small circuit, add a very large capacitor. Does that sound like what you're after?View attachment 173515
This is a lot like what I was thinking of. Back in the early 80's I installed some burglar alarms. They were activated or deactivated with a single switch pulse. Each time the relay armature was activated a beak like spring loaded protrusion would trip a cam one way then the other. With each activation it would change state. It had a microswitch on the side and the cam in the middle. I called it a "Woodpecker Relay Switch". The first time the plunger plunged it would rock the cam to the left and lock the microswitch in the on position. The next time the plunger plunged it would rock the cam back to the right and disengage the microswitch. It was the coolest relay I've ever seen. I don't know if anyone else has ever seen anything like it or might know exactly what it's called.
 

Yaakov

Joined Jan 27, 2019
1,612
This is a lot like what I was thinking of. Back in the early 80's I installed some burglar alarms. They were activated or deactivated with a single switch pulse. Each time the relay armature was activated a beak like spring loaded protrusion would trip a cam one way then the other. With each activation it would change state. It had a microswitch on the side and the cam in the middle. I called it a "Woodpecker Relay Switch". The first time the plunger plunged it would rock the cam to the left and lock the microswitch in the on position. The next time the plunger plunged it would rock the cam back to the right and disengage the microswitch. It was the coolest relay I've ever seen. I don't know if anyone else has ever seen anything like it or might know exactly what it's called.
It was probably an "impulse relay".
 
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