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The chicken coop had a very long gestation, being promised as a birthday present by my son to his mother for her birthday in August 2013. In January 2014, we started digging the foundations, and poured the concrete base (2m x 2m). Then in April 2014, the frame was erected.
But it was not until June that the netting and sides were fitted, and two small chickens, Wilma (a white Sussex) and Barney (a Barnavelda) were brought home in October. They were too small to be laying, and it was not until January while we were away for three months that our house sitters finally got some benefit from all this work!
On our return, we were donated three slightly more mature birds: Valerie (an Arucana), Joan (a Coronation Sussex), and Elinor (a Plymouth Rock). These are named after women in Beatles songs (and yes, I know that is not the way they spell Eleanor, but it is the way my sister's name is spelt, so it had to be that way).
We had a visitor for a couple of weeks: Mopsie (an Isa Brown) came from my son's yard when he was away, and we minded her. Or rather, she minded our chooks. She immediately became top of the pecking order, and bossed all the others around. I think they were glad to see her return home.
Sad Note: on 7 Nov 2015, Barney was taken by a fox. She was the one chicken that could escape from the yard, and we think she escaped on the previous morning, decided to spend the night outside the chook yard and therefore did not return to the safety of the chook house, and consequently paid the price. I buried her underneath her nest. (Unfortunately, the fox came back and dug her up again, so we had to cover the grave with bricks to stop the bloody fox digging again!!)
Even sadder note: on 17 Aug 2016, a fox entered the yard during daylight hours and killed 4 of our 5 chickens (including new resident Mopsie, from Lawn Rd). Elinor survived, as she had gone to roost, but the others were all presumably roaming outside the coop (as it was too early to shut the door). Elinor has now been moved to a safe place, and we shall not restock the chickens until we move back into the house after the rebuild. The chooks gave us a lot of fun, and we shall miss them - particularly my favourite, Valerie.
To save the hassle of having to be present every morning and every night to let the chickens out of the coop, and then close them in again once they have nestled in to roost for the night, I have constructed an automatic chook house door. This door is opened by the House Computer after sunrise and after sunset, using the Python ephem package. The delay between sunrise/sunset and opening/closing can be set independently as an arbitrary number of minutes. Currently I use 60 minutes after sunrise for opening, and 20 minutes after sunset for closing. To date, the chickens are able to cope with this regime, although they do champ at the bit to be let out. The theory is that by keeping them in a bit longer, they will get used to laying in the nesting box. However, Barney was taught bad habits by Mopsie, and flies out of the yard to lay her eggs in an inaccessible corner of the rest of the garden. So far, they have all been very good at going to roost for the night before shutting time.
This is the circuit used:
The top 2 relay contacts for each relay are the motor connections: normal polarity for the UP relay, reverse polarity for the DOWN relay. The next contact in each case is the latching contact, to ensure that the relay (and hence motor) remain energised until the door reaches the home position (either "UP" or "DOWN"). The fourth contact is an interlocking contact to ensure that both relays cannot be energised at the same time (which would thus short out the power supply).
The "UP" and "DOWN" connections go to relays controlled by the House Computer that connect them to the 12v supply for 10 seconds, thus latching the appropriate relay. These connections also go to push buttons that start the appropriate relay latchings. The connection from the UP/DOWN points are isolated by microswitches that are opened when the door reaches its limit of travel in the appropriate direction.
Here are some photos; first the Exterior view:
Then the Interior view. You can see the motor taken from an old cordless drill, driving a screw thread opening and closing drive, together with the limit microswitches on the side.
And finally, the relay controller:
The red cable connects to the House Computer, the other wires lead to the door motor and limit switches. The red pushbutton in the middle starts the UP cycle, and the black the DOWN.
As originally constructed, I had some trouble with the motor starting. It turns out, after I connected it via a metered power supply, that it wanted to draw a startup current of up to 4 amps from a 2A power supply, and the current limiting killed the starting torque. Connecting some big fat electrolytics across the power supply gave enough inrush current to get the motor turning, and it starts very reliably now.
Well, that was version 0. No sooner had I got it all working than a couple of improvements occurred to me. So here is version 1, the real version!
What are the improvements? I have done away with the up/down push buttons, partly because they were a nuisance to implement, and partly because they got hidden anyway behind the waterproofing cover. In their place, the two Up/Down pinouts will go off to a separate pushbutton assembly, as wells as the computer control relays.
Secondly, the limit switches have been moved to the ground side of the relays, swapping places with the safety interlock relay contacts. The motivation for this is that the normally open contacts can now be used as proving contacts, shorting to ground a signal line that can be used to drive indicators to confirm the open/shut status.
Otherwise, the relay contacts remain as for version 0, except that contacts 3 and 4 have been reversed on the diagram.
A further improvement is to decouple the chook door from the motor drive, and just use a gravity ledge to lower it. This means that if the door jams for any reason (a chook gets caught in it?), it will not be subject to the motor torque forcing it down on the obstruction (no premature Christmas dinners, then). The down side of this (sorry!) is that a separate proving microswitch has been added to actually show that the door is closed, rather than the motor drive has reached the limit of travel.
This system is much more reliable, and is derived from safety critical systems, such as railway signalling practice. You don't want to think that points are thrown simply because the motor has been energized! This is particular relevant in countries where points can be frozen by ice or snow. Trains crashing can be far more serious than foxes stealing chickens.
Postscript: Now that the door can be simply lifted up, the chooks have discovered this, and once the door starts opening, they poke their beaks under it, and lift it up so that they don't have to wait for the motor to finish raising it! Who said chooks were not smart! (The foxes cannot do this, because in the normally closed position, the door is behind a ledge, and there is no way to poke a nose (or beak) in to lift it.)
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17 Jan 2019
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