A probably-out-of-his-depth n00b asks: Weatherproof, "high" wattage electronics power supply?
I've got a solar measurement project I'm working on. Up until now, I've put it outside when I have a few hours to tend it, but I'd like to leave it out unattended and full time. I believe I have the mechanics and some of the electronics all worked out (I have a small model more-or-less working in breadboard mode). I originally thought the main problem here was the weatherproofing. But I think if I use a tightly sealing plastic container, well slathered with sealant and put the entire electrical part under the main body of the tracker, I should be good. Motor shaft will have to poke out somewhere, but it can remain sheltered under the tracker.
The real problem is the power supply. For the sensing part, I could just use a battery and then change it on a weekly basis, say. But the motor to move the solar tracker requires more power than that.
The way I've designed it only requires my stepper motor to take a few steps per day and it shouldn't need to be on and "locked" the rest of the time. The total power draw is low. But in order to move the large bulk for those few steps, the max amperage needs to be much higher than a 9V battery can supply. I haven't measured it exactly, but I think 1.5-2A. It's an ~8Ω motor, so the supply needs to be 12-16V.
One idea is to run an outdoor extension cord to a sheltered spot, plug a modified wall wart into it and then go from there. (The Arduino can take a max of 12V, so I might need some kind of voltage regulator in the mix to step down from 16V....?)
Another idea that I had recently was to repurpose a computer power supply. Run the plug into a sheltered spot and then use various combinations of the voltages available to run both motor and sensors. I even got a power supply to hack for this, but it's going to be some work to remove the spaghetti of extra wires and also build a special connector (I guess) to take the 20 pins and distribute them correctly. Messing around last night I also realized that heat may be a problem, at least from a computer PSU.
Thinking this must already be a solved problem, I did some googling this morning. I found
a site that sells all manner of power solutions.
For instance. But am I going to be able to plug that into the wall myself? And what about the heat problem?
Or maybe I don't need to be plugged in? (I'd sure be happier if that were the case.) With only momentary currents, maybe I can get by with, say, a dozen 9V batteries in two parallel banks of 6? This may especially be the case if I could get the motor amperage requirements down using mechanical advantage. I bought a few small pulleys but then decided that it was easier to "just increase the power" rather than attach all these pulleys, run the cord around them, waterproof all these mechanics, etc. Now I'm thinking that might be wrong after all.
Subscribe
What about a 12v sealed lead acid car battery? They're designed to provide large, brief currents to turn starter motors, so a normal car battery is good for a few hundred amps for a few tens of seconds.
You can get smaller volume batteries designed for jetskis etc if you want to get it into a tight space.
You can then just use a 5v regulator to power your sensing electronics from the same battery. Remember to put a fuse and a power switch between the battery and everything else.
posted by Mike1024 at 6:12 AM on August 21, 2008