Chickens are a tasty snack for lots of predators. It’s a tough spot in the food chain. Locally we have raccoons, possums, weasels, foxes, coyotes, neighborhood dogs, hawks, eagles, owls, my buddy Chris who loves fried chicken a little too much … Raccoons at night were my main concern.
When we first got our chickens, each night I’d walk up to the coop & close them in. That worked great until the night I’d fall asleep putting our 3 kids to bed, or start watching a late-night movie, & suddenly OOOOHH SHIT, THE CHICKENS!!! …followed by a guilty run to the coop, wondering if I was about to find sleepy hens or a poultry massacre.
A few months of this started to feel like Russian roulette. Like so many other owners of pet chickens, I decided to try building an automatic chicken coop door.
On Youtube there are plenty of automatic chicken coop doors that use string to raise/lower a guillotine-style door, sliding vertically in a track. It’s a safe design — it won’t kill chickens if one gets in the way while closing — but I was worried the door would get jammed from ice & snow.
I wanted something with a direct drive to use with a door that swung up on hinges to open. Here’s what I ended up using:
- 12V linear actuator, 8″ extension, IP65 rated w/ built-in limit switches: ~$50
- (2) 12V programmable digital timers: $7 each
- DPDT relay: $5
- 12V battery: $17
- Low-watt solar panel: $23
- 12V solar charge controller: $15 (optional)
- Misc: wiring, inline fuse holder/fuse, terminals: $6
Total cost: $115 (or $130 w/ charge controller)
Linear actuators use a small motor to move an extendable/retractable arm. The arm moves very slowly with typically 50 to 200 pounds of force. Get one with built-in limit switches & an IP65 rating so dust/water/ice/snow is no problem — pretty great for chicken coops. There are various lengths for the arm travel distance. I got the 8″ model & it takes about 20 seconds to extend/retract the arm … plenty of time for chickens to move out of the way. Small 12V actuators usually have a rating of around ~5 amps, so make sure to use a relay, fuse & wiring that’s appropriate.
Typically the actuators with higher force ratings mean slower movement, which is better in my opinion. If a chicken gets in the way of your door, a 50lb-rated actuator won’t have any different outcome than a 200lb-rated actuator.
Next, how to power it. Our coop is on wheels & we move it around our field in the summer, far away from A/C power. Linear actuators only draw a few amps so a small 12V battery will do the trick — I had an old one lying around that wouldn’t start the lawn mower anymore, but worked great for the coop.
To recharge the battery, I used a small 1.25W 12V solar panel. Since the panel’s watts are so low, it acts as a trickle charger, & that way you may not need a solar charge controller as long as the panel is in direct sunlight for most of the day. I’d still recommend a charge controller to make sure the panel doesn’t have a net drain effect on the battery in winter or other low-light conditions.
Last challenge was for the door to open in the morning & close in the evening. I went with a simple setup with very low power draw: two programmable 12V timers. The first timer (the “power timer”) switches on twice a day for 1 minute each to provide power. The second timer (the “reversing timer”) is programmed to energize a DPDT relay concurrently during one of those power timer events — the relay reverses polarity to the actuator so it opens instead of closes the coop door.
The last piece is a 12V DPDT relay wired as an H-bridge. This type of relay has 4 sets of +/- pins:
- normally closed (NC)
- normally open (NO)
With this relay, energizing the relay coil switches the circuit connecting the common from the NC pins to the NO pins. For the H-bridge setup:
- connect the battery (+/-) to both timers, with a fuse holder on the (+) wire.
- connect the power timer output (+) to an NC pin.
- jump the same power timer output (+) to an NO pin, but with opposite polarity.
- connect the reversing timer (+) to a coil pin (doesn’t matter which one).
- connect the linear actuator (+/-) to the common pins.
- connect ground (-) to the remaining open pins on NC, NO, & coil.
If you wired it correctly, the +/- leads for the NC/NO pins form an “X”.
Next, program the timers so their clocks are set identically. Let them sit for a few days & figure out which timer is faster than the other. Use the faster timer for the reversing timer.
Power timer: set for two daily events (morning & night) of 1 minute each. For example, 6:30AM- 6:31AM and 9:00PM – 9:01PM.
Reversing timer: Set to run concurrently with one power timer event, so it comes on sooner & stays on longer than the power timer. For example, 6:30AM – 6:35AM. I prefer the morning run so if anything goes wrong it only means the door won’t open (no big deal).
Make sure to check the timers after a few weeks to make sure they are keeping identical time. I was surprised to find my timers get about 20 seconds off from each other per month. So I set the reversing timer to stay on for 5 minutes — energizing the relay is a very small drain on the battery. That way, the system can run for a year before I’d have to reset the timer clocks… I change the timer settings 3-4 times a year anyway, to adjust for daylight.