Latching Relay with Single Input


Joined Mar 14, 2008
You can easily do that if you don't mind adding a CMOS IC flip-flop and a few added components to control a DPDT standard relay.

Sim of example circuit below:

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Joined Jan 27, 2019
Welcome to AAC.

What will this relay be doing and why? (What problem is it intended to solve?)
What voltage do you expect it to operate at?
How much current will it have to handle?


Joined Jan 23, 2018
A "latching relay" is not an adequate description.
I can describe a single input latching relay that works with only one momentary switch input. But it has no means to unlatch. So it meets the description, but that is probably not what the TS wants.
You can get alternate action relays from many suppliers that will provide alternate ON/OFF with each pulse.Not super cheap, but no additional parts required.


Joined Jul 18, 2013
Do you want a relay flip-flop circuit using one PB, Push-on/Push-off.
I have the circuit archived if needed.
NO IC. required.


Joined Jan 23, 2018
Reverse engineering even simple PCB assemblies is a skill built after learning about circuits and especially about components. A serious challenge for beginners, especially discerning relay pin-outs.


Joined Jun 8, 2013
I’ve purchased a few of different kinds of these types of modules. The product user information usually isn’t in an obvious location but exists. The price and availability makes looking for it not so bad, for me anyway.


Joined Dec 29, 2020
I have a circuit to drive a single coil latching relay if required. It requires two inputs though: a pulse on input A to latch the relay on. A pulse on input B to latch the relay off. The advantage is that the state of the relay is known at the time the pulse was ended, and the inputs will ignore simultaneous pulses.


Joined Sep 11, 2014
I need a latching relay with single input.
It's known as an 'impulse' or 'ratchet relay'.

The impulse / ratchet relay is set on application of a single pulse input to it's coil and reset on the subsequent pulse.

In other words, an impulse / ratchet relay alternately sets and resets with pulse inputs to its coil.

Here's an animation, courtesy, that gives an idea of how the impulse relay works.

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Joined Jan 23, 2018
On/Off maintained position relays with a single mains-rated contact, operating on 24 volts, have been around for a long time. They were used for controlling lighting in the era before 3-way switches became common.
It seems that I must locate a current supplier and post a link for any to pay attention to this bit of information.