I am wondering if there is a certain label or naming convention for a relay that can mechanically hold its contact state after the coil is de-energized. I thought this is what a "latching" relay does, but after some googling, it looks like latching relays hold their state by opening/closing a current path for a secondary coil. I would like for there to be no power consumed by the relay once the switch has changed state. Does such a device exist?
Electronic – name for relay that holds state and only consumes power when toggling states
relay
Related Solutions
Anything that switches rapidly can cause a pop. Here's an example of a switch that is "popless" because it gradually changes the attenuation (courtesy of Vampire Squid Labs).
Some audio mux chips have a zero cross switching function built in which performs a similar function.
All this hanging contacts around the relay coil can and does work .The red and green start and stop buttons seen in machine shops are older than me .There is another way that uses the fact that the pull in voltage is always much greater than the dropout voltage .Get your relay and a DC power source thats the same as the coil volts .The relay coil will off course pull in reliably.Now place a series resister thats the same as the coil resistance in your relay coil power supply circuit.The coil now only gets 6V and wont pull in .If you momentarily short the resister the coil will pull in .If you momentarily remove the power the relay will drop out .So you can make a normal relay have a bistable latch function .The time to do this rather than the orthodox approach is when you need the contacts for other things and you are not worried about power.I have tried this with small DC relays but have not done this on AC relays.
Best Answer
As others say, a latching relay will stay in its last set poition without power.
The latching relays you mention, that need power to hold in one state, are better described as relays with a self-latching contact or circuit. One application for this sort of latching system is as a relay controlling a motor - when you push the "start" button, the relay pulls in, and one contact closes to maintain power on the coil when you release the button. If power fails, the relay releases, and the motor will not start unexpectedly when power is restored.