A little help please - automatic chicken coop door

[Robbus]

Hi All,
Newbie here. I'm trying to build an automatic chicken coop door using an automatic car window unit...as cheaply as possible. I've got the motor with arm, a 12v dc power supply, a timer (and a photo cell), and DPDT (8-pin) relay. I want the door to open in the morning (via timer or photocell) and close at night. Can this be done with what I've got? If yes, how do I wire it? If no, what is the cheapest solution?
I had it working with an automatic antenna but it worked differently and proved to be of insufficient strength. I've noodle over this second option and can't work it out in my head (even with the Google)
Hope somebody can help.
Cheers,
Robb

 

[Robbus]

Addition: y'all probably already know this but the window motor is polarity reversing so I guess the add-on question is can I use this DPDT relay by itself to reverse polarity?

 

[MikeMl]

This has come up lots of times on these forums. Start reading here.

 

[dr pepper]

You can get cheap 12v timers such as this:
**broken link removed**
And you'd need a couple relays and some limit switches, the link mike posted is a good start.
Youc an do away with limit switches and use a thermal circuit breaker, but thats getting a bit more complex.

 

[cowboybob]

Welcome to ETO, robbus!

plug "chicken coop door" into the "search" window (top right of this page).

 

[KeepItSimpleStupid]

Check out the threads on chicken coop door as was suggested.

Search for "astronomic timer". These can open.close based on calculaitng sunrise and sunset, usually +- time. So you can have lights come on 30 min after sunset and off at 11:30 PM.

The limit switch approach is normally used with 3 relays. Two make the limit switch much lower current with (UP/Down)/NOT Brake type of signals. The third relay takes an ON/OFF and converts it into an UP/DOWN type of signal.

Automotive relays are cheap and can be had with plugs. I think some can be purchased already wired for door locks. It's the same principle.

 

[alec_t]

Car window winders can be quite powerful, so you may wish to add a safety feature to prevent hens being beheaded. There will always be one hen determined to get itself trapped as the door closes .
Remember to design your door mechanism such that chicken crap doesn't build up and prevent correct operation.

 

[AnalogKid]

It almost always takes two relays, one for direction and one for power, or one relay and two limit switches, one at each end of the range of travel. Controlling them can be a microprocessor or some logic chips or a simple lamp timer from WalMart.

ak