My garage door opener has output terminals that output 10V as idle and 24V when the opener is running. I have the output connected to a 24V relay to control the lighting in the garage. My problem is that the 10V idle voltage is enough to keep the relay closed.

My thought was to insert a 20V 5W zenerdiode to get rid of the 10V idle voltage, however, my concern is voltage loss across the zenerdiode is too great for the relay to be able to close when the output terminals produce 24V.

Am I right in my concerns or will this solution work?

I'd like to solve this problem using a passive circuit, but any solutions are welcome.

  • 3
    \$\begingroup\$ Perhaps you would include the datasheet for the relay. \$\endgroup\$ – scorpdaddy Apr 29 at 11:52
  • \$\begingroup\$ think along your solution :do you have a reason to use this specific 20V zener ? a 10V zener seems a better idea. \$\endgroup\$ – Navaro Apr 29 at 11:56
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    \$\begingroup\$ The 24 V relay might not engage reliably when you lower the coil voltage. A more robust solution would be to use a 12 V relay in series with a 12 V zener diode. Then at a 10 V signal, there will be almost 0 V across the relay. Note that the zener will dissipate some power, it needs to be able to handle that. You could also split the zener in 2x 6 V, 3 x 4 V etc. \$\endgroup\$ – Bimpelrekkie Apr 29 at 11:59
  • \$\begingroup\$ Thank you all. I can see the reason for using a 12 V zener and a 12 V relay, unfortunately, I already bought the 24 V relay because I thought it would be enough. Datasheet for the zener in mind is here: elektronik-lavpris.dk/files/sup114/1N5333B-D.PDF \$\endgroup\$ – mowol Apr 29 at 12:06
  • \$\begingroup\$ And the datasheet for the relay? \$\endgroup\$ – scorpdaddy Apr 29 at 12:09

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