Does anybody know how the electric window motors know when/how to stop?

I have a window motor that I am using for a project, has nothing to do with a vehicle, and I am trying to figure out how these motors know when to stop, ie. when a window is fully closed. There does not appear to be any micro switches so I am assuming the motor knows when the voltage changes as the glass meets resistance...?

I realize they will stop when the center console button is released but with the drives door window one push automatically operates the window, so how does it stop? Thanks for any insight.

 

There must be a current-sense circuit somewhere; not sure if it's in the motor assembly or upstream. When the motor stalls it will draw more current; circuitry senses this and some kind of current limiter kicks-in introducing a high resistance into the motor's current path.

You'll be dinking with it so you'll tell us..

 

The drivers window switch is different and has a sensing circuit in it. The other windows have no clue. In the evening, with the vehicle in park and lights ON hit the "up" on a window that's already up and you'll see the lights dim. They dim because the motor is ON and it's trying to push the glass up through the top of the door. The other three motors have no clue if the window is up, down, half way or missing entirely.

 

"dinking" with it, haven't heard that phrase for a while...

Your right though, I will figure out how it works eventually but thought I might ask and save myself a step........

FYI I am using this motor and the window arm actuator for an automatic chicken coop door opener, runs off a 12 volt battery with a solar panel charger and an RV thermostat timer...........

 

There is a relay under the center console to make the auto down feature work. Some people install a duplicate for the passenger side to do the same, and a triplicate to get the window to auto up (which is not very safe) and another for the sun roof. I plan to do the mod for my front passenger side since we have no small kids.

 

Likely forced to stop. You may want to install a travel micro switch to cut the ground when travel is far enough.

Those motors are super strong so warn the chickens, you don't want to have one loose their head prematurely. Lol

 

Here is a write up on adding the auto down feature to passenger side.

http://www.matthewsvolvosite.com/for...hp?f=1&t=38606

 

Thanks guys, I guess I need to look at putting a micro switch into the system somewhere to cut the power when opening or closing as per RSPI suggested.....

 

current-sense circuit for the drivers and load stop for the rest.