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Garage door opening after power failure

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Maybe ,either the relay driving the motor up is stuck or the transistor driving the relay has shorted.
I've repaired several GDOs with shorted transistors after lightning strikes.
Perhaps multiple failures from a power surge.
Just a guess.
HAve fun


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Does it do it every time?
Does it do it when you cut and restore power intentionally in calm weather?



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Good point Tony. I remember a Single Board Computer I used in the 80's that worked with a switching 5V supply, but would not work with a linear one. I was controlling motors and they ran away. I was able to fix it by replacing an inverter IC with a schmidt trigger version. The IC was socketed.

RESET sometimes needs a good edge (fast rising) trigger.

Simple reset circuits might just be a resistor to Vcc and a capacitor to ground. They are unreliable.

I'd try replacing that with a real POR (Power On Reset) IC or a Voltage Detector.


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I was working at the construction of a major bank head office when the power failed. All the door locks unlocked to allow the people working in there to get out. The designers never thought about robbers causing a power failure so they can get in.
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