Small 12V DC timers

draines
draines Registered Users Posts: 17
Hello all-

I am looking at powering some 6W (DC) lights in a chicken coop. There will be two lights in two coops...24W total.
I'm planning on running the lights about 4 hours a day (96WH) off a battery and panel setup. (37Ah and 50W panel/PWM controller)(~25% DOD)
This is my first solar setup I am attempting.

I would like to control the lights via a programmable timer, and notice they range in their "consumption" from 4.4VA to 12VA. (Timer Referenced http://www.amazon.com/gp/product/B00AY7BGJI/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=AL7LHK6Q9LVTS)

Two questions:
1) I know there is some difference between VA and Watts, but sometimes the same. In this case, can I assume they are similar? I want to be sure that I am understanding what my actual usage will be...the "VA" is throwing me off.

2) Are there any other options I am overlooking for this function? I thought of using a light sensor, but then I still need an 'auto-off' after 4 hours.

Hopefully I didn't say anything stupid!! :) Thanks in advance!
Dan

Comments

  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    Re: Small 12V DC timers

    The trouble with using that timer is it runs on 12Vac not DC (thus the VA spec). Its needs AC as the output circuit no doubt uses triacs. Its too bad because all these low cost timers are like this. (irrigation timers especially) A programmable timer that runs on 12Vdc is much more expensive.
  • draines
    draines Registered Users Posts: 17
    Re: Small 12V DC timers

    Ah...I did not catch that...thank you! I have noticed the $$ on other DC timers. Guess I'll have to actually turn the power off with a physical switch. I guess it saves me about 110WH/day at least by not using a timer.
    Thanks again for your input!
  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    Re: Small 12V DC timers

    I recently purchased the timer linked in the OP (a few bucks cheaper here). The specs for it are indeed confusing. The back of the unit says the following:

    POWER 12V DC/AC
    16A(8 )A,250 VAC

    The sheet that came with the unit says nothing about DC. Says voltage rating is "AC 220V" and voltage limit is "AC 180V~250V." It's a poorly written generic instruction sheet that includes wiring diagrams for 3 different units.

    I haven't tried my timer yet, I had planned on using it to turn a small 12V fan on and off. This person seems to be having success using this same timer to open and close a chicken coop door using a small solar set up using what I assume is a 12V battery. The reviews at the above Amazon link also suggest other folks are having success using 12V batteries as the power source.

    I'll still plan on trying mine out. If it works, great. If it doesn't, I'm just out a few bucks.
  • Mustang65
    Mustang65 Solar Expert Posts: 42 ✭✭
    Re: Small 12V DC timers

    Dan,
    If you can read a SIMPLE wiring schematic, plug in a relay card, you can build your own SMART timer/monitor. Programming it (sketches) is simple, even for the non-programmer and there are many forums out there, with sample sketches you can use and if you can not locate the exact sketch you need, the people on the forum will gladly walk you through your sketch needs.

    The ARDUINO Uno can do what you want and more. The ARDUINO Uno in a programmable micro-controller that is used for teaching students how to build electronic circuits. In your case it would be a basic timer circuit. The ARDUINO could handle that easily. Ahhhh, but you may want to add a light sensor to activate the timer, no problem there. How about a temperature and humidity sensor for the chicken coop(s)? Temperature gets to cold or to hot. Add a RED light on the outside of the chicken coops to let you know if it is to cold/hot, or your interior lights are not functioning, or the door is open, maybe a remote alarm circuit.... the possibilities are only limited to what you can dream up.

    Start out simple with a light timer circuit and then move on to enhance your project.

    Easy to learn, fun to build. If I was able to learn it ANYONE can!! There are a lot of sites out there that sell the Arduino Uno, but you need to be careful of cheap knockoffs, as they are prone to having issues. I use Adafruit, see links below. They also have a great support forum, in case you may need some assistance and they have sketches for all their products, which is a life/time saver. http://www.adafruit.com/
    The main Arduino site is http://forum.arduino.cc, check it out.

    I am working on a few monitoring project for my RV, reading/logging the Morningstar MPPT data, alarm, battery status data, water tank(s) levels. Just something I enjoy while being retired.....
    Don

    PARTS LIST (with options)

    Start with:
    (1) (Arduino Uno micro controller $24.95) http://www.adafruit.com/product/50
    (1) (Arduino Relay Shield $14.90) http://www.robotmesh.com/relay-shield-for-arduino?gclid=CM-P27rspcACFQxp7AodP0cAfA

    Future Enhancements:
    (1) (Light Sensor – Photo Cell $0.95)
    http://www.adafruit.com/products/161

    (1) (Temperature Sensor $1.50)
    http://www.adafruit.com/products/165
    Or
    (1) Temperature/Humidity Sensor $9.95)
    http://www.adafruit.com/products/385

    (1) (Real time clock $9.00)
    https://learn.adafruit.com/ds1307-real-time-clock-breakout-board-kit
  • Plowman
    Plowman Solar Expert Posts: 203 ✭✭✭✭✭
    Re: Small 12V DC timers

    I installed my 12V DC timer a couple weeks ago. It's been working fine, no problems at all. I'm just using it to run a large 12V computer fan to vent a cargo trailer during the day. Have it running from 8 am to 8 pm.

    I have it connected to my battery bus bars, using a cheap inline blade fuse holder with 5 amp fuse for circuit protection. Wire size in this circuit varies from 10 AGW to 14 AGW, mostly 10 AGW, total length is <10 feet.

    The instruction sheet says self-consumption of the unit is "2 VA (max)", which I believe is 0.17 amps @ 12V. I just took some readings when the fan is running, self-consumption of the timer appears to be 0.09 amps while running a 0.06 amp fan. Hard to get consistent values with such low amperage using my clamp meter. Total draw on this circuit was ~0.15 amps.

    The timer looks well made on the outside. Took a minute or two to figure out how to program it, it has an excessive number of settings, but guess I'd rather have too many than too few. For the price, these timers seem like a bargain. I put Anderson Powerpoles on mine to be able to easily move it around.

    I suspect the first thing to give out will be the LED screen, I've had some issues with cheap LED screens on clocks stored in a trailer with a wide temperature and humidity range. Not sure if this is reparable, but for a $5 timer it probably wouldn't be worth it.

    Instructions say "resistive load capacity" is 16 A @ 250 VAC, and maximum "lamp load" is 2000W. These ratings seem generous for such a small unit with unknown internal wiring, but regardless it'll work fine for my low amperage DC loads.

    Generic picture of timer in question:

    51tc17fXbDL._SY355_.jpg