Latched On/Off to Momentary with Reverse Polarity by State

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=144972
Printed Date: May 12, 2025 at 11:02 AM

Topic: Latched On/Off to Momentary with Reverse Polarity by State

Posted By: blewis9991
Subject: Latched On/Off to Momentary with Reverse Polarity by State
Date Posted: November 22, 2018 at 3:17 PM

Hi

The solenoid I currently use in my RV is continuously on when engaged and draws 3.7amps of power which is a lot when there is no external source of power. So I have a new solenoid that latches on and off and draws no power once in the final state, but it uses a momentary input that must switch polarities each push.

The diagram for the latched on/off relay giving a momentary pulse in the relay section will work for the on state, but not the off state.

The new solenoid opens with a pulse of +12v to terminal 1 and ground to terminal 2. The solenoid closes (switches state) with a pulse of 12v on terminal 2 and a ground on terminal 1. I have a on/off switch in place for these signals. I can't change the switch because other circuitry depends on the on/off state.

Can someone suggest a schematic for this please.

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Thank you for the advice

Robert

Replies:

Posted By: eguru
Date Posted: November 22, 2018 at 5:45 PM

Change the switch to 3PDT (ON-ON) switch.
Wire two of the center terminals to a 100uF NON-Polarized capacitor in series with the relay coil.
Wire those end terminals to your positive and negative wires.

+     C       -

-     R       +

X     X       X

Use the remaining set of contacts for the other dependent circuitry.

Posted By: blewis9991
Date Posted: November 23, 2018 at 7:02 AM

Thank you for your reply. I am having difficulty understanding the wiring.

I wire a capacitor across the two end terminals with the 12v to the one side of the capacitor and the other to ground, then connect the relays + and - to the center two terminals, then use the remaining terminals marked X X X for the exiting wires. Is this correct?

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Thank you for the advice

Robert

Posted By: eguru
Date Posted: November 23, 2018 at 8:22 AM

blewis9991 wrote:

Thank you for your reply. I am having difficulty understanding the wiring.

I wire a capacitor across the two end terminals with the 12v to the one side of the capacitor and the other to ground, then connect the relays + and - to the center two terminals, then use the remaining terminals marked X X X for the exiting wires. Is this correct?

Almost correct. You wire capacitor terminal 1 to "C". Capacitor terminal 2 connects to one of the relay coil terminals.

The remaining relay coil terminal connects to "R".

Sorry, I didn't have time to draw this out for you.

Posted By: eguru
Date Posted: November 27, 2018 at 8:26 PM

Did you get your project working?