I am planning on using this old craftsman garage door opener as a motor for the purpose of raising and lowering some stairs. Given the weight of the stairs I am planning on setting up a more favorable gear ratio for the motor, however, this requires it to run for longer than it usually would.

I have removed the plastic gear mechanism that tells the motor when the door has reached it's final location. I was hoping to preserve the rest of the circuitry and not have to hotwire the motor so to speak. To do this I was just going to have these existing contacts be triggered when the stairs reach the up/down position.

HOWEVER: even with this contact mechanism removed, the motor will only activate for a certain number of seconds before it is deactivated, as if the contacts were triggered. I was wondering what kind of other mechanisms the garage door opener might use to deactivate itself after a set number of turns. Anyone know?

I have noticed there is some kind of IR sensor which detects the motor's movement. I was wondering if there was some kind of counter in the logic board that would use this sensor to count up to the maximum allowable turns, then deactivate the motor. I tried to trick it by covering some of the holes with tape, but it seems to be primarely used to assure a certain motor speed so changing what it thinks the speed is causes the motor to deactivate.

Hope one of you knows enough information about how these are designed to help me out! Otherwise, I will have to make my own motor control circuit and forget about the existing one.

Thanks in advance.