A question that comes up a lot in my Automatic Chicken Coop Door posts is what’s the wiring diagram with a photocell? Ask & ye shall receive!

One thing I’ll say up front while I still have your attention — the wiring diagram above is NOT WRONG. The photocell wiring is not what you’d expect. The black wire is positive, white is ground, & red is the switched output (+).

This is a “dusk till dawn” photocell which means the photocell switches on at night. It’s advertised as waterproof & the light sensitivity is adjustable. It also has fairly mediocre reviews on Amazon so if anyone has a better photocell to recommend, please do!

Here’s the parts list:

The DPDT relay is wired as an H-bridge. This means you make an “X” with power to the normally open (NO) & normally closed (NC) terminals so they have reverse polarity from each other. The “common” terminals connect to the linear actuator.

The photocell controls the coil, the coil switches the relay & that reverses the motor. The linear actuator’s built-in limit switches take care of the rest.

IF IT OPENS AT NIGHT & CLOSES IN DAYLIGHT: Flip the leads to the linear actuator where they plug into the relay.

POWER DRAIN: Although daytime power usage is minimal (0.004 amps) when the photocell is only monitoring the light level, the photocell & relay have a constant power drain at night of 0.12 amps when both the photocell & DPDT relay coils are energized. So I recommend only using this photocell system on dedicated power.

You can still use the photocell system with a solar panel/battery setup, but you would need enough capacity to handle the power drain (12 hours night @ 0.12 amps = ~1.5 amp-hours just for operating the photocell). If you need to conserve power, use this timer-driven system instead.

Here’s a video explaining the wiring:

OPTIONAL TIMER OVERRIDE: Don’t trust the photocell? Add a timer so that closing the door happens regardless of whether the photocell works. Here’s a wiring diagram for that:

Set up one timer event:

  • start time = forces the door to close
  • end time = door available for photocell to open

So for example, start time of 10pm & end time of 5am.

Keep in mind the timer only overrides closing — if you have a bad photocell that doesn’t recognize daylight, the timer won’t force the door to open.

I use a system of timers instead of this photocell system, because where I live has high winds & I’m concerned the photocell wouldn’t be reliable with blowing dust & snow. The timer system also has far less power drain which is useful if you have a solar-powered coop. I change the open & close times every few months to keep pace with daylight. But the photocell method is pretty slick & if it works for you, great.

Any questions, post in the comments below. Hope this helps!