Problem with Chamberlain HD900D

I just installed my refurbished Garadget unit. No issues connecting to my wifi and I have a pulsing cyan LED as expected. I believe I have the unit wired correctly to the first two connectors but its not working consistently. It will open the garage but it will not close it. If I short the 2 wires with a screw driver the door opens or closes as expected.

What Garadget does to open the door is exactly the same thing that it does to closed it - momentarily shorts the connected terminals simulating push on the button. Is there a difference if you wait for short time after opening garage before attempting to close it?

You can try increasing the push time from 0.3 to 0.5s.

Finally got it to work. I ended up having to adjust the Relay On Time to .7 seconds.


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Help, I also have a Chamberlain HD900D. Instead of a doorbell button actuator, it has a control panel that will sense motion, show the temp of the garage, lock the opener, display the time, etc. and has a button that operates the opener. My Garadget was wired as shown here. Shorting the wires at the blue connectors will operate the opener (but not always, I think. It’s hard to tell if I made a good connection every time and for the necessary length of time). But the Garadget will not trigger the opener. I’ve tried changing the “push time” to all possible selections. I checked the Garadget with an ohm meter and it does indicate a closed circuit for the correct time when I trigger it from my phone. I can hear the relay clicking. But sometimes it would click twice. Lastly, I checked the wires with a volt meter (disconnected from the Garadget but still connected to the opener) and it showed 15 volts. I suspect the HD900D feeds power to the control unit so it will do all of the things mentioned above (and which I couldn’t care less about). I have no idea if the button on that unit operates the opener by completing the circuit or sending some other signal. If the trigger wire has a constant 15v, it doesn’t seem like a good idea to close that circuit, depending on the amps. Maybe the HD900D is sophisticated enough to shut off the power during the short. Is it time for the work-around?

Per our email conversation it looks like the best course of action in your case is to use the wireless remote for triggering the opener.

Thanks for your prompt and valuable assistance. I did wire it to a keychain remote that works flawlessly. The low power my opener was sending through the door button wires was causing the Garadget to protect itself by tripping a circuit breaker. The system is performing great and has not given me any false information and has opened or closed my door every time. Even through Alexa, which was remarkably easy to set up. I love how she says “OK” to my commands and then says “hold on” while the door moves, and then says “The door is closed (or open)”. She sends the command but waits to verify that it was carried out.

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