Easy to use + cheap light sensor / timer switch for 12v?

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Easy to use + cheap light sensor / timer switch for 12v?

Postby Shoeshine » Tue Jul 06, 2010 8:57 pm

OK this is silly automation overkill, but I just have to play around with this and if it worked, would be oh so cool.

I am bringing a deep cycle battery/solar charger setup this year for a 12v power system. I am going to be running mostly EL wire/LEDs and a homemade bucket swamp cooler.

What I am hoping is that someone has a line on 12v photosenstive switches or timers that could turn off my lights and turn on my cooler at daybreak.

A quick run to the local bigbox resulted in only 120v AC timers/switches.

And My Google-Fu must be weak today because the only 12v timers I have found online are either scientific instruments running at the minnimum $85 each or electronic componants (Arduino, etc...) that require circuit board building and/or programming that is beyond my scope to learn for this year.

It seems there must be a simpler and cost effective solution out there, especially as I can buy a 120v timer for $4, but so far no luck.

Any thoughts?

Thanks in advance,
Chris
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Postby rodiponer » Tue Jul 06, 2010 10:47 pm

Hi Shoeshine--

Sailing suppliers have something called a "Night Watchmen", a 12 volt photo electric switch. Google says these cost $35 and up, depending on where you buy it from.
http://www.kansaswindpower.net/dc_accessories.htm
http://aeesolar.com/catalog/products/H_ASW_LG_LC_PH.htm

For your EL wire inverter, I think it is important that you get the on/off "Night Watchmen" style rather than the electric dimmer style that gradually turns on at night by varying the voltage. Some EL wire inverters might hate being fed a low voltage during sunrise and sunset. Mine, at least, will start to flicker and seem to get much hotter than normal at very low voltages.

Some solar charge controllers have an output to turn on lights at night. They don't have an electric eye, they detect night through the solar panels. These can be nice because they have a low voltage disconnect, so that they won't let the lights completely drain the battery and damage it. Check out this one, $38, can handle 15 amps of solar panels, and has "16 programmable timers for lights and etc." Their in-stock/out-of-stock status changes quite a bit, so if you have smaller solar panels you could wait until the less expensive lower capacity one is back in stock:
http://www.virtualvillage.com/15a-12v-p ... 8-060.html

Though their website sucks, I have ordered a lot of stuff from Virtual Village for my mutant vehicle and have been very happy with how fast stuff arrives in the mail from Hong Kong (generally a week).

The solar suppliers have DC timers that are just like the AC timers, but more expensive-- $50-75, depending on if it is the LCD kind or the kind with the spinning disc:
http://store.solar-electric.com/fldctico.html (for the LCD kind)

For your swamp cooler, I think the ultimate is some kind of industrial Omron style cycle timer. I use one on my CNC mill to control a solenoid that blows chips away and am so happy with it. With one of these on your swamp cooler you could set it to 3 minutes on/5 minutes off, and easily adjust that with a twist of the knobs. That would save a whole heap of electricity and water. You can't really do that with a 24 hour timer. With two you could even have one on the water pump, since to wet the pads you may only need to run the little impeller pump for 5 seconds every 30 seconds, or something like that. McMaster and etc want to sell the expensive super-variable ones (from 0.01s to 300 hours), but there are cheaper models that have less of a wide time range (1-90 seconds or whatever).
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Postby Token » Tue Jul 06, 2010 11:35 pm

Go to the Home Despot or bLowes and get a single solar garden light that has two batteries in it (3V).

Go to DigiKey and order two micro relay switches that run on 3V.

Here is an example:

http://parts.digikey.com/1/parts/755644 ... -l-3v.html

Hack the solar light and attach one relay coil to the solar panel directly (this runs the swamp cooler). Replace the LED with the second relay coil (this is the night time lights)

The relays run 33 mA on the coil nominal so should work just fine in a solar light.

Total cost is $4 for the relays plus the cost of the lantern (under $10).

Or you could do it the right way as Rodiponer suggested.
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Postby Token » Tue Jul 06, 2010 11:50 pm

Oops, that relay is SPDT so you only need one.

Sine Pole Double Throw

Image
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Postby Token » Wed Jul 07, 2010 12:00 am

Shit, now that I think about it, you only need the single relay.

If you connect the relay coil to the solar panel before the built in diode the solar panel will do the switching for you.

If you can't find the diode or would rather not open the solar panel, an additional low voltage drop power diode can be installed anywhere between the solar panel and the positive battery terminal.

You would need a 12v relay but I'll let you search that out on your own at Digikey.
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Postby Shoeshine » Wed Jul 07, 2010 1:02 am

Nice...

Rodi:

That DC multi channel timer from solar-electric was similar to the best options I have found so far, but thanks for the link, it is a little cheaper.

At first glance it seems the timer would be the better option. the more I think about it, what I would want in a practical/ideal world, would be to have the lights go off about a 1/2hr before full light. They are primarily camp deco, and a lighted icon stuck up on a high pole to guide me home. Likewise the swamp cooler really only needs to kick in a couple of hours after dawn. I have an insulated hxayurt and though I have not yet used the cooler in playa conditions, I am anticipating I will really just want it to run in the 8:30ish to noon range. (ahhh extra sleep... glorious)

Now I just need to figure out if the budget will support automating what I can do by rolling over and flipping a switch.

P.S. I see you are in SD. Me too. U-heights/hillcrest. and funny enough I run a CNC machine as well, though a router rather than a mill. Nice thought on the cycle timer for chip clearance. I assume compressed air?

Token:

I love the way you think. Hadn't even occured to me to use a cheap PV panel as a sensor. I have a few laying around. I will have to buy a couple of those relays just to hack away at em. I might not end up using them. [see my thinking above] though if I dont buy a timer, it might be the way I go if only for the lights, and manually control the cooler. The lights surprisingly are the bigger draw than the cooler. It would definately help my total power bottom line to make sure they killed at dawn even if away from camp.

Anway thanks for the input. Ill post as the get the bugs out.

Chris
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Postby rodiponer » Wed Jul 07, 2010 10:06 am

Shoeshine wrote:P.S. I see you are in SD. Me too. U-heights/hillcrest. and funny enough I run a CNC machine as well, though a router rather than a mill. Nice thought on the cycle timer for chip clearance. I assume compressed air?


Yes, I have a girly little compressor that can't blow continuously. So the Omron cycle timer pulses the solenoid to blow compressed air every few seconds. It clears the chips really well.

I would so be into a CNC router if I had a larger garage. Or a cleaner garage with more room. After the mutant vehicle I want to make an aluminum proa (a Polynesian outrigger canoe thing) that breaks down into thirds and nests, to be the pen-ultimate dinghy for the next time we go sailing.
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Postby kman » Wed Jul 07, 2010 10:35 am

Shoeshine: We're in the same boat, so be sure to share your final solution! :)

(me also=new hexayurt, solar panels, battery, fans and lights, and maybe a bucket cooler!)
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Postby Talynt » Wed Jul 07, 2010 12:06 pm

For those of you lurkers without much electrical experience, what’s being discussed here is actually pretty simple. A switch makes and breaks a physical electrical connection (meaning that a piece of metal is sliding around, generally). A relay is basically a glorified switch. You solder it inline on the circuit you want to control the way you would any switch, but instead of having a button to push or flick, the way to make it connect and disconnect is by applying power to a 2nd set of terminals. The trick is it usually uses very, very little energy to turn “onâ€
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Postby gyre » Sat Jul 10, 2010 9:24 am

I think home automation might have some useful stuff.
Water control is often in 12 volts.
Solar supplies have been mentioned.

I think the larger photocontrols are actually voltage neutral, lowering resistance to throw a switch.
Maybe the switch part is voltage specific?
Might be possible to modify it?
I like the Fisher-pierce for twist lock and the large Tork model for a wire in type (can be screwed into a piece of conduit).

Alarm controls are almost always DC.
I know there are timers available now, long and short term.
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Postby Token » Sat Jul 10, 2010 9:39 am

You could also use a cheap thermostat.

The old Hg and spring don't care about voltage much.
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