Hi,

Thanks for looking, I building a chicken coop and want to encorporate a DC motor to open and close a small door bassed on a timer.

Any help or ideas would be great.

Thanks

Jason

 

Welcome to the AAC forum.

This seems to be an unmet market need.

If you search this forum for "chicken" you'll find several related threads. A key issue is what sort of power you have available (battery, solar, regular AC, etc.)

 

Well it needs to be solar, so dc, and on a timer.

I have read the forums on similar ways but most are using a light meter, which is not always reliable when cloudy.

I am new to electrics but I learn fast, I would just like someone to talk to as I feel I can and should be able to do this.

Thank you

Jason

 

Well, I actually did this and it worked for many years. Until the chicken house started falling to bits and we had to get a new one. Thought it was time to re-design the door opener and, guess what, I haven't got round to it yet! But, hey it's only been a year so far!

The hardest bit for me is the mechanical part of the device. Everything was made of scrap that I found. My original unit had a small DC motor with a high ratio gearbox. This was connected to a shaft with a miniature toothed belt. Cord wound round this shaft lifted the door.

The ratio of the gearbox was so high that the door stayed up when the motor was not powered. You need 2 limit switches to stop the door. I did this by using a large brass bolt and nut. I cut the head off the bolt and drilled a hole right through it and mounted it on the shaft. The nut which was prevented from turning, then moved along as the door went up and down. I mounted 2 small micro-switches that were operated by the nut at the limits of the door travel. This way, the whole thing including the limit switches was built inside a waterproof diecast box with the cord coming out of a small slot in the bottom.

For the electronics: I used a PIC micro-controller operating a pair of relays for the motor. The limit switches go to two inputs. The light sensor was a resistive photocell. This was connected to one of the on-chip comparators on the PIC.

I had to do a bit of research: measure the resistance of the photocell as it got dark and find out what the resistance was when the chickens decided to "go to bed"! I used a timer (in software) to make the door close about 30mins after this just to be sure that they were all in. My door opener ran from a 12V rechargeable battery. Worked for about 2-3 months between charges. To minimise the power consumption, my PIC went to sleep and woke up (with the watchdog timer) every so often to test the light level.

Sorry to go on. Get building. (And I will too - very soon).

I have got a very nice little DC motor with a worm drive output which will not wind back - which is just waiting to be used!

 

Does your device need to only latch and unlatch the door, or actually move the door's position? The power required to move the door is greater than just a latch.

For the timer, I wonder if you could use a commercial lamp timer. I have a cheap one with a battery powered clock and "computer" that appears to function just fine all by itself, without being plugged in. It's not like the old-fashioned kind that runs off of AC. It would probably be easy to power this with a solar cell, and this one cheap device could handle all the timing functions. I don't know if it can switch a, say, 12v, load on and off, but I suspect it could.

Then you just need a two-position solenoid or such to perform the mechanical flip-flop functions. I have no experience with such things but I'm sure there are some good ideas available here.

 

Ok, Thank you both for replying. I have an electric screwdriver powered by 4 "AA"'s 1.5v each so 6v, that turns both ways. I also have a digital mains timer that is programmable. I have found "6V 200mA 1.2W Solar Panel" on ebay. Would that be ok?

I am starting from scratch, but I'm getting there. I know you need a diode after the solar panel to stop the flow from battery back to the panel. I know that the limit switches stop the motor once the door is in the right position.

Questions:
How would you make the motor change directions?
How do you use the timer to start the motor?
I've seen people using a couple of magnets for limit switches, could they be used?

Thanks you guys, really want to get this working.

Jason

 

It sounds like you will need a couple of microswitches, similar to what garage door openers use, for motor stops. It could be reed switches with magnets as you suggested. I would avoid relays like the plague, they are not very power conservative, but you may need to build some simple logic to determine directions. I don't think reed switches could take the motor current, but I could be wrong about that. If you run into problems any number of us can show you how to use them to drive transistors that will take the brunt of the current.

 

A couple of thoughts .... because I will be doing this myself.
Use a disk based door, ballanced, so the drive can be simple friction on the outer rim.
This will not harm a bird then should it trap one, which I apriciate is not likely anyway.
You only need one limmit then, like winscreen whipers used to have, read two points on the disk 180Deg apart (closed / Open) and stop if you reach either, two would work as well - drive to closed or open as applicable but still in the same direction.
Start with a pulse long enough to drive past the limit so that when the pulse is remoced you will drive to the next limit.
A battery powered central heating room stat with a simple timer, night setback, will provide timed opening / closing but could probably be modified to read light in place of temp.
Result open during the day timed, closed outside this period based on light level?

Havnt thought all the details through yet but it seems a reasonable strating point and its mechanically simple with off the shelf controls, well almost!
Alistair

 

Its surprising I had no response when I started a similar thread some days back.

Anyway, hope to learn something from this thread.

 

I have an electric screwdriver powered by 4 "AA"'s 1.5v each so 6v, that turns both ways. I also have a digital mains timer that is programmable. I have found "6V 200mA 1.2W Solar Panel" on ebay. Would that be ok?

Since you want a 6V system to run your motor you'll need to charge a 6V battery. The 6V panel won't charge a 6V battery very well. You need the panel to be at a higher voltage than the battery so that the current will flow into the battery (e.g. for a 12V battery panels put out 18-22V). If you size the system correctly then you won't have to worry about overcharging because the panel won't push hard enough to overcharge and damage your battery. This battery would be more than enough:

http://www.allelectronics.com/make-a-store/item/GC-64/6-VOLT-4.5-AH-GEL-CELL//1.html

If you want to go really cheap you can make your own panel from factory second .5V cells you can find on ebay.