How many Amps are needed to operate a "12 volt car antenna" automatic coop door?

[jimmywalt]

I'm going to make an automatic door opener on a timer for my chicken coop with a car antenna. I found many places on BYC and Youtube that detail how to build one. Unfortunately there are conflicting answers as to how what type of power supply (amount of amps) it would take to power the antenna.

I've read 12 volt & 5 amps (and these supplies are near to impossible to find at a reasonable price) and I also read the wii game power adapters that are 12 volt 3.7 amps will work.

I want to go with as inexpensive as possible to get the job done.

So who out here has either made a car antenna door and how many amps is yours, or who knows how many amps a car antenna would take to work?

Here are the plans that I'm going to use :
https://www.backyardchickens.com/a/automatic-pop-hole-opener

Thank you very much for your help!!!

 

[VallejoSheltie]

That really depends upon the antenna.
If new, it should include documentation on current draw.

If it doesn't, just attach it to your car battery, and a multimeter and check it.
Your multimeter should have a second Common/Ground input that you plug the black wire into, and it should be labeled 10A.
The normal Common that you use for voltage usually has a limit of 200ma, which would blow if you try to measure 3-5 amps.

 

[jimmywalt]

That really depends upon the antenna. If new, it should include documentation on current draw. If it doesn't, just attach it to your car battery, and a multimeter and check it. Your multimeter should have a second Common/Ground input that you plug the black wire into, and it should be labeled 10A. The normal Common that you use for voltage usually has a limit of 200ma, which would blow if you try to measure 3-5 amps.

Thank you for your reply. I'm not sure I entirely understand.

The antenna is from a junk yard out of an old car, so no documentation.

The antenna has 3 wires. One that's ground, One that's hot all the time and one that turns hot when the radio is turned on.

So how can I hook this up to a multimeter to determine the amps?

Thank you again!

 

[moetrout]

I have a store bought auto door. I have it hook up to a 12v motorcycle battery. The motorcycle battery has a float charger on it to keep it fresh. The advantage of doing this is that even if the power goes out (1 hour or even 1 day) the pop door still opens and closes. In your case if you did this the current draw/amperage is no longer an issue. Plenty of amps can be supplier by a MC battery. Good luck whatever you choose to do!

 

[VallejoSheltie]

Argh, good idea again.

I am doing similar with a 12v UPS battery (12v/7Ah) that will be recharged with a small solar panel.

For the OP, moetrout's suggestion is perfect.

120v power to trickle charger to battery to antenna motor + & - .
The one question I would have is, if you connect the radio lead to the 12v +, does the mast go down when you remove it? I would assume that is how it works. So, the only other thing you need to do is figure out how to have it make that connection for 12-14 hours during daylight.

Mechanically, you could look at my other recent reply to an autodoor thread, however it is rather gimmicky.

Electronically:
I would think a cadmium sulfide cell connected to a solid state relay would meet your needs very cheaply.
You would want a non-latching relay I believe.

So again, you connect +/- from battery to the antenna.
You need to get your parts onto some sort of board, or use a cheap plastic breadboard, or stripboard (Google these).
You will connect the CdS cell to the SSD Relay, and the Relay output to your Radio lead.

I'm not really an electronics guy, however I suspect moetrout may chime in.
Here is a simply CsD LED circuit that you can look at. I think it may be more complicated that even what you need, with the transistor there...
http://www.evilmadscientist.com/2007/a-simple-and-cheap-dark-detecting-led-circuit/

Actually, I guess you can't just use the CdS to pass through current, you have to use it to signal a transistor which will pass that current.
So the example is what you need. Looks like parts costs should be several bucks at most, probably more for shipping.

And, my normal go to guys Electronics Goldmine have no SSD relays, which seem to be more expensive than I remember. However they do have one here: http://www.goldmine-elec-products.com/prodinfo.asp?number=G15187 which is only $1.49 and spec sheets online says it is NO Normally Open which is what you want.

CdS cells are here, mostly the same though I'd get one that has the higher Mega-Ohm rating when dark out.
http://www.goldmine-elec-products.com/searchprods.asp

Proto board to put your components, although you could just solder them all together "Dead Bug Style";
http://www.goldmine-elec-products.com/prodinfo.asp?number=G18056

Let me know if you are interested, and I'll try to help out further.

 

[jimmywalt]

Thanks everyone for your help. Here's what I have set up and it works great (inside my house). Hopefully this weekend I can try to install it in the coop.

 

[jimmywalt]

Also note that two 12 VCD power supplies (one @ 1.2 amps, the other @ 1.3 amps) works just fine. Hopefully they will continue to work with the little resistance from the door (which will open and close HORIZONTALLY)

 

[VallejoSheltie]

Cool, mine is also going to open horizontally.

Not sure about running 2 grounds from different PUS's though. If there were to be a fire, your insurance company might not cover damage....
Maybe someone with more electrical experience can chime in.

 

[VallejoSheltie]

PSU's.

 

[jimmywalt]

Cool, mine is also going to open horizontally.

Not sure about running 2 grounds from different PUS's though. If there were to be a fire, your insurance company might not cover damage....
Maybe someone with more electrical experience can chime in.

My coop is only 4x4x4 with 5 chickens. "If" a fire we won't contact the insurance company. The coop only cost about $300 to build.

I don't see a problem with 2 PSU's providing the ground for the 1 ground wire from the antenna.

Thank you.