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.
- 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?