Wireless Doorbell - triggered by a relay, won't stop

[avguru]

I recently installed a 2N IP door station at a gate and I'd like to provide a simple "Ding-Dong" inside the house to notify when someone rings the gate station button. My home automation system will send push notifications to phones and tablets but it's still nice to have an audible notice.

My thought was to get a wireless doorbell, solder wires onto the terminals of the mini push button switch of the transmitter and attach those to the relay outputs of my home automation system.

It works, when the relay closes, the chimes ring. GREAT! BUT the problem is that when the relay opens, the chime keeps ringing. If I put my voltmeter across the terminals of the relay I see that they close and open properly so why would the chime keep going?

Coincidentally, when I put the voltmeter across the terminals of the relay, the ringing stops.

The doorbell transmitter is powered by a 3V CR2032 battery.

Is there possibly some residual current passing through the relay even when it's open? Is there a minimum spec. on what can be connected to the relay outputs?

Any thoughts or suggestions would be appreciated.

Thanks

 

[bernardgreen]

The leads from the push button to the relay contacts and the relay contacts are picking up radio frequency energy. The circuitry of the transmitter is designed to tolerate only short connections from chip to push button and thus is very unlikley to have suppression of that input. The radio transmission from the transmitter most likely being picked up by the extended leads and re-triggering the transmitter.

You might have sucess if you fit a reed relay very close to the transmitter and operate the coil of this relay by a voltage from the home automation system.

Any alteration to a License Exempt radio transmitter unit contravenes the regulations for the use of Licence Exempt equipment.

 

[avguru]

Very interesting....I hadn't thought of that at all.

I did try one thing though. I installed a diode in series and that seems to have fixed the issue. Nothing else has been changed, ie. physical layout or orientation of circuitry with respect to other components.

It's beyond my knowledge as to why this seems to be working. I hope that I'm not screwing something else up in the meantime.

 

[oldbutnotdead]

If it works and all your other stuff works then don't worry about it.
Not sure about the RF bit, possibly you're getting some back EMF from the relay coil (as it opens the circuit) inducing sufficient current in the pair to the wireless bellpush to continue triggering it. Usual deal with that is a reverse diode across the relay coil but if your diode in series is working then leave it be.

 

[Lectrician]

Honeywell do a wireless door bell with hard wired push button.

https://www.tlc-direct.co.uk/Products/DC915SCV.html

 

[avguru]

I should have definitely looked for that solution first. Thanks