Relpol relay (non-latching) - help needed!

JeremyGelber · Nov 1, 2018

Hi,

I purchased a relay and relay base in order to control my doorbell whilst using a Nest Hello: the Nest product takes 24V, whereas the doorbell only wants 8V. So the relay closes the circuit when receiving power from the Nest and the doorbell is separately powered by an 8V transformer.

All fine, and it works the first time. However, the relay REMAINS ON after the doorbell has been pressed. That isn't what I wanted! What I want is for the relay to turn off straight away, so it's ready for the next press.

The relay I'm using is part number R15-2012-23-5024-WTL. I've actually tried 2 of them thinking the first one was faulty, but the issue exists with both. This is described as "DPDT Non-Latching Relay Plug In, 24V ac Coil" so should be the correct one.

I have the 24V supply going into pins 2 and 7, and the relay coming out from 1 and 3. My base has 2 places labelled "7", one of which has an up-and-down arrow on it. But if I try to use that one, nothing happens at all - I had thought perhaps that was the non-latching pin.

Any help would be HUGELY welcome with this fairly straight-forward issue.

Thank you,

Jeremy

JeremyGelber · Nov 1, 2018

Pictures attached in case it helps:

JeremyGelber · Nov 1, 2018

Just realised the arrows only signify IEC vs NEMA wiring numbers - d'oh! So still stuck....

Lucien Nunes · Nov 1, 2018

The 24V power supply is DC, but the coil of that relay is designed for AC. Therefore, its resistance is too low and the current through it is too high at 24V, which I suspect it magnetising it to the point that it sticks on. Replace the relay with one that has a 24V DC coil...

E2A, how are you making the relay go off again after it is stuck on?

Lucien Nunes · Nov 1, 2018

Ah, wait. The Nest Hello specifies 16-24V AC. So it is your 24V DC power supply that is wrong. Probably, the output is a little triac or something which only switches off at the AC current zeroes. Given DC, the internal electronics still work but the output doesn't switch off.

E2A, the thick plottens. I've never handled the Nest products at all but I think the Hello is designed to integrate with existing doorbell wiring, where the pushbutton is in series with the bell / chime. The Nest door-mounted camera and electronics therefore have to be powered parasitically via the bell, so they provide a thing called a 'Chime Connector' which I suspect is a small electronic module to bypass sufficient current around the bell coil to power the camera without affecting the bell operation.

If you are not using this, or if the relay is too sensitive (it requires much less current to operate than the bell itself), then the standing current needed for the wifi electronics may be enough to hold the relay on, although not enough to pull it in until the button is pressed.

Are you using the chime connector?

JeremyGelber · Nov 1, 2018

I am using the chime connector. You’re saying I’ve used the wrong transformer, but it looks like an AC transformer no? If I managed to buy the wrong one then I’m an idiot.....

Lucien Nunes · Nov 1, 2018

It's definitely a DC power supply. Clues include: 24V [DC symbol] 1.25A, 'DC OK' light, + & - markings on the terminals, and the voltage adjustment (AC transformers aren't adjustable).