Irving said:

I don't understand how the counterweight works

Suppose the door weighs 200g (in a hanging configuration). A motor would have to lift all that weight. But if the door was counter balanced with a 150g weight then the motor only has to work hard enough to lift 50g. Upon loss of power the heavier door will pull closed.

Thanks, I know how a counterweight works, I just couldn't see how Extranet's description of it worked, because he didn't mean the counterweight but the door weight.

 

EDITING DRAWING. WILL POST WHEN CORRECT.

 

OK, after much head banging, I think I have it right.

 

I like the hanging door idea. The bottom of the door needs a guide at the extremities to stop it being rotated off the runners. To stop an intelligent fox breaking in I'd propose a pawl latch at the top of the door. Once rolled into the closed position the pawl drops locking the door. As separate motor/solenoid raises the pawl to unlock the door, or it could be cable driven from the main door motor via a simple clutch arrangement.

 

Some interesting points to consider.

My only concern with a solar panel is on an overcast day the door won't open?
A suitable outdoor panel is for 12v 19w is ~£20?

OK, after much head banging, I think I have it right.

View attachment 208847

You are proposing a limit switch top and bottom of the door?

 

Almost like a small scale automatic garage door opener.

 

Some interesting points to consider.

My only concern with a solar panel is on an overcast day the door won't open?
A suitable outdoor panel is for 12v 19w is ~£20?

With a simple solar panel solution you'll always have that situation, esp in UK where sun can't be relied upon day by day, but most weeks will give enough to keep a battery topped up.

Either the drop door or hanging door approach will work and easy enough to engineer but you will need a locking mechanism to keep foxes out as they could easily move a lightweight door and you need to keep the weight down to maximise battery life.

The electronics is easy enough, I can easily adapt the Arduino solution I have for my automatic front door opener. How far from your house is the chicken coop?

 

You are proposing a limit switch top and bottom of the door?

Yes. If there are no limit switches at both ends then the motor, driven by batteries, will drain the batteries.

As to the fox thing - the door can close into a pocket that won't allow it to be pulled open. And if you're concerned about the fox swinging the door open along the slides - depending on how you choose to connect the door to the motor - a design such as a worm gear drive could prevent the door from being opened by any means other than the rotation of the motor shaft and worm gear. Unless a fox has had formal training and education in electrical engineering I doubt the fox would be able to defeat such an arrangement.

Yes, I know the sun and clouds are not all that reliable; but so would a light sensor. Yes, the PVP (Photo Voltaic Panel) would be more problematic than a light sensor, but this approach is something I personally would consider. Rather, more directly, I'd consider the PVP to keep charge on batteries that open and close the door and the control for opening and closing would be a clock timer. At a given hour the door opens. At a given hour the door closes. As for the change in seasons and solar duration - I'd have to reprogram the times, but that's easy enough to accomplish simply by resetting the open and close times. I have lights in the living room that are on a timer. In the morning the house is lit before I get out of bed so I don't stumble around in the dark. Then when the morning sun has had enough time to rise into the sky the lights go off. At night the lights come on at a specific time until an hour when we usually go to bed. If we stay up past that time we have other lights we can manually turn on and off. I have to change the programming on this timer three times a year. It wouldn't be any harder to do the same thing with the coop door.

 

Funny, I just looked up "battery powered timer switch" in Amazon and found this: Only $16 US.

On the main page it came up with this page: Of course this one is ready made and costs over $200 US; so I understand the desire to build your own.

Also tried looking for a timer with a remote control. Didn't find one. "(

 

train one as such

 

What do you do if at dusk the coop door closes and chickens are still in the yard?

 

Look up astronomic timer. Some small PLC's have them. I've seen a low voltage Chinese one. I use one of these timers to turn on a light an hour after dusk and off at 11:30. Mine glitches for a day during the switches to/from daylight savings time. Mine is for 120 VAC and it contains an integrated battery backup just for time keeping.

 

What do you do if at dusk the coop door closes and chickens are still in the yard?

Yes, there will always be stragglers. So you build the de-luxe door mechanism which incoporates a chicken-recogniser and counter and only closes the door when all the birds have been counted in .

 

My thoughts IMHO. Both would use solar power to keep the batteries charged, as that just makes good sense. The battery's purpose is to supply current on demand for short period and then have long charge period.

You can use a mechanism that lifts the door to a catch, and the catch holds the door up until the catch is released allowing the door to simply fall closed- this utilizes gravity for closing the door, and the motor to simply lift it. I think this might be the easiest and most robust solution. Can be driven with relatively small motor.

However, perhaps a better solution which does not care much about weight or muck, is that you simply use a motor to drive a chain that turns screwed shafts on both sides of the door. 'dumb-waiter' switch circuits have been designed elsewhere in the forum to handle travel direction. Current could be used to determine when motor reaches limit. It provides positive control of the door in both directions, eliminates most of the torque issue. Possible use a laser or I/R sensor to determine if a chicken is in the doorway so it isn't trapped/killed on close.