I do not need the voltage to ground from the battery end. I do not need the voltage to ground from the door controller end. I do not need the voltage to someplace in the many ground connections. I do not need the voltage that sags because the battery voltage goes down when current flows. I do not need the voltage from one end of a wire that is connected to another wire of a different gauge. I do not need the voltage across a splice.

Much like the measurement across the night watchman, I do not need the voltage to ground. I do not need the voltage to ground from the input. I do not need the voltage to ground from the output. I do not need the voltage to ground.

I need the voltage from someplace on one wire to someplace else on the same wire, several feet apart, while it is carrying maximum current. No splices allowed.

Just choose 2 places on the main 12 gauge feed wire and alligator the voltmeter leads on to it. Measure the distance between the two points you connected to. Cycle the window controller and notice the voltage on the voltmeter. The distance, the wire gauge, and the voltage will tell me the current.

 

Sorry, misunderstood. Distance on 12 ga fine stranded wire is 6' 3 5/8" - open cycle = .039 and close cycle = .019 on the 2V scale.

 

I believe the next scale down and the last on my voltmeter is 200mA. Would you rather have it in that scale? If so, I'll get it tomorrow morning.

 

That means the current required to open the door is 3.9 amps. To close the door requires 1.9 amps. Much less than we expected! Still, there WILL be a start surge. All motors do that.

Now we can plan on a small battery charger/eliminator, in the neighborhood of 5 amps. Much cheaper than a 20 amp charger. In fact, so small that it might be hard to find one that small.

A ten amp, slow blow fuse, or even a 20 amp fuse, is probably the right thing to do for the long run. After all, everything is wired for 20 amps, so there is no risk of melted wires with a properly sized fuse. Caution: even a 20 amp fuse will blow if the door mechanism jams. Keep your slides smooth (Candle wax makes a good lubricant for wood and the chickens will not be interested in it, it has no food value and it is not toxic.)

This will also allow a wider selection of relays. There are a lot more 10 amp DPST or DPDT relays available than 20 amp relays. I did find a relay that will stop the braking problem, but it's a bit pricey and not the style you started with. (I put it in post #98.) It's just as good as those car relays except I'm afraid it isn't dust proof.

 

I just saw your offer to try a 200 milliamp scale to measure voltage. Absolutely not!

Now, if you have a 200 millivolt scale, that would be more accurate. However, I think we have it close enough at "less than 5 amps". Besides, if the current is less than 10 amps, you can use your meter to measure it directly! No measuring and calculating. Just use the 10 amp DC scale and hook it up. Forget the 5 amp fuse test. Just use the meter as it was intended to be used.

ps, I haven't said anything about a float charger because I can do that with my calculator tied behind my back.

I think Radio Shack sells a 4 amp "battery eliminator". Do you have one? No, don't try to run the motor with it.

Another idea: I've seen temperature sensitive vent openers for green houses. If you installed one in the roof of the chicken coop it might save you from coming home to roasted chickens. Not roosted, roasted, as in baked.

 

Here's a plan for wiring the backup system.
Includes a nice, fat, diode for less than a dollar that will blow any fuse you put in and still survive.
The way this works, if the charger ever drops below the battery voltage by 6/10 volt, or drops out completely, the battery will take over.

http://www.mouser.com/ProductDetail/Vishay-Semiconductors/VS-20TT100/?qs=sGAEpiMZZMtvcUztdGSumNhYraL2URsYWKKiydBBpec%3d

 

In reference to post #104:
The battery eliminator can be one of higher amperage that is more common and therefore should be a little cheaper as long as it doesn't hurt anything.
The relays need to be dust proof. Even though they are in an enclosure, chickens aren't the tidiest housekeepers and generate quite a bit of dust. I'd also like to be able to buy a panel or socket just to keep everything neat and tidy and with everything set up as "plug-n-play" will make working on everything much easier.
The door operates on ball bearing drawer glides which are essentially linear bearings and keeps everything tight and rolling smoothly. The other bonus is they are "self emptying" meaning that if any debris were to get in them (very highly unlikely) they are open on the bottom and will clear themselves. The only thing that can really get into them is dust.

In reference to post #105:
I meant mV, I had amps on the brain since that is what we were ultimately trying to measure.
This coop is highly insulated with a very good ventilation system in it already. When temps were 108, the inside temp was between 10 and 20 degrees cooler depending on how cool the previous night was. Winter is yet to be experienced but should be much warmer without any heat added. It is quite comfortable and if it wasn't for the obvious inhabitants and purpose, one could quite comfortably live in it.

In reference to post #106:
Does this system maintain the battery? I'll have to get a shopping list when everything is finalized. I do have a radio shack in town and the net is close by also. Todd

 

Here is a photo of the door. The wires are left out and will be tidied up once my switch gets here and everything will be enclosed in the box.

 

All the other chickens will be jealous. Your chickens have sheet metal and thick plastic and bearings and electricity for their house!

We're not in Kansas any more, Toto.

Oh wait...we are.

ps, Yes, the drawing in 106 shows a float charge regulator to maintain the charge in the battery. If the battery ever does get used, the load on the battery will be a small percentage of its ability. I'll calculate "maximum number of days without power" later. and don't worry about the mulit-amp charger maintaining the battery. If it isn't just wonderful, you can maintain the float charge with a wall wart.

Meanwhile, try a few runs with your 10 amp DC meter connected between battery positive and the main feed wire to the controller. That will prove whether the millivolt measuring method was accurate and remove doubts about what size charger to buy.

 

The range on my scale is 2A all the way down to 20 micro amps. I don't have a scale that allows anything stronger than 2A.

 

I guess you didn't buy the $4 meter at Harbor Freight

I also guess we'll have to believe the 3.9 amp measurement we already have.
Want to try the 5 amp fuse test?

Edit: Gotta go. My real life demands my attention.

 

Nope, it's an old sears. I can if that's the way you would like to go. My switch arrived so I'm going to go solder it in. I like the way my inner cover panel turned out; I'll post a pic a little later. Todd

 

and I like the way you used a plastic cutting board for a door. I have one just like that in my kitchen.

 

Yep, HDPE - doesn't move with changes in humidity or temperature, basically weatherproof, strong, lightweight, easily milled, and fairly inexpensive. Cutting boards are a quick cheap source for it.

 

Mine must be a different kind of plastic. When I run hot water on one side (during washing) it warps like crazy.

 

Automatic door and now the chickens want hot water?

Why does a chicken coop have two doors?







If it had four doors it would be a sedan.