Design of door mechanism

Hi folks,

I’m trying to design an automated door for my chicken coop. While I think I have a grasp on the electronic components of the design, I’m struggling with the mechanical aspects, and was hoping someone could give me some insight. I’ve considered a couple of different mechanical designs, which I’ll enumerate below.

Some constraints:

  • The load will way 1-2 kilos.
  • The opening speed is not critical.
  • I would like to be able to operate it for extended periods on LiPo or LiIon batteries, so low power is good.
  • It will be operating in a very dirty/dusty environment, and I’d prefer to achieve low maintenance needs. Rugged is good.
  • Minimizing cost is always a good thing.

Design 1 - Draw bridge
Pretty straightforward. The “door” is effectively a drawbridge that is raised/lowered by extending/retracting cords that link to its top/outer edge. Rejected this idea because I don’t like the idea of having mechanism parts exposed to the chickens during the day.

Design 2 - Vertical slide
The next obvious idea is to have the door raise/lower vertically within the confines of the coop, via cord extended/retracted by a motor in the roof. One challenge here is the need to maintain a holding torque while the door is raised. I considered using a Tamiya worm-gearbox for this, but I’m not convince that it’s either strong or durable enough for this. Maybe a stepper would be better? Or using a counter-weight?

Design 3 - Horizontal slide
Rather than having the door slide vertically, I could have it slide horizontally. This would require more mechanical bits to enable the sliding, but would remove the need for holding torque. I haven’t really figured out how this one would work yet.

Design 4 - Linear actuation
Both design 2 and design 3 could be realized with a linear actuator rather than a cord system. But, while mechanically simple, those things are expensive, power-hungry, and way over-powered for what I need.

So, any ideas?


I do not see anything obviously wrong with any of those designs. While the linear actuators we carry might be a little too much for that kind of application, they do have an IP rating, which means their water and dust resistance is characterized to a certain standard, and could be worth more consideration if you are worried about the system being durable and low maintenance.

Your project sounds pretty cool; we’d love to hear about it once you get it working.