Garage Door controller reverse function

[Dan_68]

Hi all,

I have recently installed a garage door with a motor. My problem is i dont have a controller for the motor. I dont want to change the motor as it is very difficult to do so.
I have bought a 2ch wireless reciever with remotes. I can connect these up no worries to control the door and i am going to wire in the limit switches to the relays to tell when the door has reach the top and bottom.
Does any one know how the reverse function works on a normal controller, ie when it hits an object it stops or reverses. I know some have light beams but others must work on a over current reading or something.

Any help will be appreciated.

Thanks

 

[TonyS]

Many years ago I brought a Sears (US) one to Europe. That had a synchronous motor with a perforated disc that chopped the light to a photo transistor. The motor ran at constant speed until the limit switches were reached. When it slowed down, because of an obstruction, a comparator circuit that measured the light pulses triggered the reverse operation. I had to fit a new disc because of the change from 60 to 50 cycles!

 

[Dan_68]

thanks mate taken me a while to find this post again. Pretty clever system it must know to use it on the down stroke as well as you would think it would slow a bit lifting the door as the weight of the door changes the more it goes up.

 

[Gryd3]

thanks mate taken me a while to find this post again. Pretty clever system it must know to use it on the down stroke as well as you would think it would slow a bit lifting the door as the weight of the door changes the more it goes up.

There are multiple systems you can use.
We have a larger door at a shop that has an bladder on the bottom. When it compresses, it stops the motor. Of course, we have an up, down, and stop button so we can manually dictate which direction to move it or even stop it half way.

 

[Bluejets]

Late model stuff generally senses current draw to control the motor.

 

[Tha fios agaibh]

Aside from photoeyes types, there is also edge sensor (weatherstrip at bottom of door with pressure switch in it) and older style doors use a limit switch that is on the track. When excess force is applied from downward force it makes the track bar move back and trip the limit switch.

 

[Tha fios agaibh]

If you have the spare parts this is doable, but if you plan on buying everything it will cost nearly twice as much as buying a new opener for $150
If your willing to ignore the reversing function (unsafe) it can be done with 4 relays for under $50