Selecting a motor
@breimann , all of that will take a few posts to explain. Bear with me.
The door mechanism took a lot of trial and error. My biggest advise is to estimate the torque needed to open the door before ordering any components.
Due to lack of a dynamometer, here is how I tackled the problem :
Attach an elastic band to the door at some position where you know the distance to the hinges (15cm in my case)
Pulls the elastic band towards you in a right angle to the door until the door starts to move. Measure or estimate how much the elastic band is stretched (in my case, I measured +/-30cm). Be careful the door doesn't smach into your face
Disconnect the elastic band from the door and suspend some adjustable weight to it until it is stretched the same amount as before. I used a small bottle, an iron wire and changed the amount of water in the bottle.
Measure the weight
The torque is distance (to the hinges) x the weight, in my case 15cm x 0.285kg = 4.275 kg.cm
I selected a Modelcraft RB350600-0A101R Transmissiemotor 12 V 1:600 (25€ at Conrad).
According to the datasheet, at 3.44kg.cm (closest in the list), the motor should run at 9,46 rpm and consume 0,14A (12V).
In reality, the motor takes about 3,5s to make half a turn, which amounts to 8,6 rpm and pulls between 150 and 200mA with a startup current of +/- 350mA. Pretty close to what the data sheet says !
For the actuation of the motor, I use two relays of a Seeeduino relay shield of which I connected the NO to 0V, the NC to 12V and each motor wire to one of the COM. The resulting behavior is
R1 open, R2 open ==> motor stops
R1 closed, R2 open ==> motor turns CW
R1 open, R2 closed ==> motor turns CCW
R1 closed, R2 closed==> motor stops
Some more advise,
Don't try to open the door with a stepper motor. i tried it and I got bad oscillations.
A servo motor could also work, but you'll have to find one that can deliver the torque.
@stefaanv Thank you for the explanation. It's something I want to test.
@stefaanv this is very very helpful. I really appreciate your detailed explanation. Obviously you have really thought it through and have tried various ways to "skin the cat" so to speak! Again, thankyou. In my case i'm looking at having around 6 chooks and our chook house will be a bit bigger. I'm also planning to make it big enough for one of us (my family - my wife, 3 kids) to go in there and clean it out etc. It will all be constructed out of recycled materials i've been salvaging. One thought i have is in terms of the door making it a sliding door possibly with some sort of latch to lock it?
If you have enough height, your best option is a vertically sliding door. Check out http://www.beschermjekippen.be/ for inspiration. In my case it was not an option because the ched is not high enough.
For easy cleaning, I've put the bottom plate of the ched on sliders. Once a month I slide out the bottom, put an bucket underneath and push the wood chips and dropping into the bucket with a broom. The wood chips are nice because these prevent that the droppings stick to the floor. I didn't invent all this myself, stole the ideas in a few animal shops.
By the way, in which part of the world is a chicken called a "chook" ???
That's a really clever idea. Any possibility of getting some photos of the bottom of the shed sliding out and how that works? Cleaning chook yards is always a thankless task so anything that can be incorporated into the design before hand to help that would be fantastic.
Hi @stefaanv, just wondering how the automated chicken coop is going? Did you manage to get your holiday in and did you have a good break? How did the system perform?
Yes, worked smoothly during the holidays. Having a short video at door closing time is very comforting.
The system is still working fine but one of the chickens sometimes forgets to go indoor. Next redesign will be to make the closing time configurable from the controller and to do something smart with the LED light.
Still need to refactor the program in OOP style as well.
Playtime has been limited lately
I doo see that the battery voltage is a lot lower now then it was during summer time. Still need to do some testing with the smart sleep mode as well.
@stefaanv Hi there, how is your coup going now? I've just pulled down an old kids cubby house at a friend who is moving, and put it back up on our farm. So I'm getting ready to build my auto doors etc.