Dr. Frankenstein's Latching Relay

Sam Klennert
2 min read
Someone recently called our Technical Support hotline to see if we have a latching relay for their application. Their application was to turn some lights on and off in a medical facility. They had a momentary switch with no voltage (dry switch). They needed the switch to provide a latched 24Vac signal to control a separate device. Basically, the first press and release of the switch would activate the 24Vac. The second press and release of the switch would deactivate the 24Vac. The momentary switch was a Form C contact (Single-pole, Double-throw).

After scouring our website for the right product solution, nothing came up to work. The customer was in a situation where they would need some kind of solution and cost was not too much of a concern. I began rubbing my hands together in a maniacal fashion as I thought of all the ways to latch a 24Vac output. After half the day testing and wiring, here was the cost-effective solution I landed on for this customer in the application they were facing:

RIBMN24C Diagram

Products used in this setup:

  • RIBMN24C-4T
  • RIBMN24C - you need quantity five (5) of the RIBMN24C relays to make this bad boy work
  • A 24Vac transformer for input power to the circuit

As indicated in the diagram above, the SPDT switch on the right-hand side of the wiring diagram will short the pink line to 24Vac Common (the little triangle symbol), which latches/un-latches the 24Vac output on the purple line. Explaining the circuit can get long-winded here, so feel free to reach out to us for an in-depth explanation. The bottom line was it worked! Cue mad scientist-like laugh

It was great to do some problem solving with that customer, so feel free to reach out to us for help with anything RIB relay-related. The crazier the better!