Help with a 12v control ciorcuit

when a test circuit is energized, I need to be able to send a 12 volt current MOMENTARILY to a latching relay in another circuit. currently it is wired with a relay that sends a continuous voltage which the latching relay cannot handle. i need to send a "blip" of power that shuts off automatically until reset that activates the latching relay. i am a good mechanic but a total noob when it comes to this type of thing- is there an easy way to do this?

August 26, 2023

Multiple ways to do it. Here an example with a single PMOS (plus passive components).

To see it in action, [Simulate][Time Domain][Run Time-Domain Simulation]

The width of the pulse is proportional to the product R1 (in Ohm) times C1 (in Farad). Note that capacitors have a high tolerance in value and many are dependent of the temperature.

You push the momentary push button SW1 to reset the system.

How it works? Quite simple, when the impulse of the clocked voltage starts, it starts to charge the capacitor which, in time, will make the PMOS cutting off the circuit (when

Vgate_pmos + Vgs(th)_pmos = Vs_pmos


Use a PMOS which can sustain the 12 Volt (requirement easy to meet) when it cutoff the circuit, and your amperage (depending on the load), when it is allowing the pulse to occur.

You may use a variable resistor as R1 so you can fine tune the pulse duration to the shortest possible pulse which still turns on your load (the relay, I assume).

by vanderghast
August 31, 2023

Note that if you push down SW1 while the source is still supplying a voltage, you end with a continuous pulse (which will kill the relay, here, the load, if I understand you correctly).

The easiest way to prevent that kind of incident seems to be to use a DPDT switch instead of the momentary push button.

Make the "ON" position closing the positive side of the source to the path to R1 and the PMOS (M1) for terminal 1, and let terminal floating but connected to R2. Make the "OFF" position disconnecting terminal 1 from the source but connecting terminal 2 to the gate of the PMOS to R2.

by vanderghast
August 31, 2023

3 Answers

Answer by gdalmolin

This is all you need to generate a momentary pulse for your latching relay. It will be much easier to wire than dealing with semiconductors. Then input can either be continuous, or momentary. And will provide a pulse for your latching relay.

+1 vote
by gdalmolin
September 02, 2023

Answer by weberralph

Use a 12V power supply able to provide adequate current for dino game your application. A wall adapter or battery can work.

+1 vote
by weberralph
September 05, 2023

Answer by JenniferMitchell

Hello everyone!

+1 vote
by JenniferMitchell
September 28, 2023

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