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I don't know if this is the place to ask but I figure it can't hurt. I have built this crazy art piece for burning man that needs around 360 leds. I am going to have 4 differant circuits that require a string of 90 leds each . I figure I have to wire them in series/parallel. I was hoping to use a deep cycle 12V car battery to power all of these LEDs. 270 of these leds are 3.6 V 30 mA RGBs and 90 of them are 4.5 V 30 mA UV LEDSs. So my questions are 1. Will a 12 V deep cycle car battery power all these LEDs for 10 hours at a time? 2 Is the series/parallel method best for this project and conserving energy? and 3. I will be hot gluing the led lens and then sticking them into a clear film canister so will this cause to much heat? Keep in mind these will be used at night time at around 45 to 60 degrees while flying through the air. Any help would be greatly appreciated. I need to have this done within the next week. If there is someone whoe has extra time to talk to me my number is 719 439 6433 call me ANY time. Or email me. Thanks
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Re: Burning Man Project with 360 Leds NEED HELP PRONTO
Mon, August 14, 2006 - 11:54 PMIf this were my project, I'd wire them in parallel. Series and parallel are distinct methods of organizing the loads on a circuit - in series would go something like this
[positive lead] - LED - LED - LED - [negative lead]
The problem with this method is that the second LED is drawing power from the first LED's negative lead, etc. So if one LED fails, the whole string goes down. It's not likely with LEDs, but anything's possible.
Parallel would go something like this
[positive lead] [negative lead]
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+ - LED - +
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+ - LED - +
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+ - LED - +
If one LED goes out, it's not a big deal. Also, I wiring in series sometimes causes a drop in current travelling down the line. I haven't worked with LEDs, but I understand they can be pretty sensitive, and need to get the right input.
As to whether or not a car battery can power them... Probably. An event gig I did a while ago involved LED uplights using a lot of LEDs (thirtyish - not like your numbers,) that were powered by AA batteries. I'd be inclined just to try it and see if it works, but if you want to take a more mathematical approach... A lot of batteries have a rating in amp hours. If it's a 12V battery, you need to figure out your systems draw in amps at 12V and divide the battery's rating by that number. You'll end up with the number of hours the system will run, assuming that nothing is wasted generating heat or something. Some is always wasted. The RGB batteries draw 3.6V * 30 mA each - a little over a tenth of a watt. 270 of them draw 29.16 watts. The UV LEDs draw 4.5V * 30mA each - a bit more. 90 of them draw 12.15 watts. So the total draw for your system is 41.31 watts. But you need to know your draw in amps at 12V. It's a little short of 3.5A. In order to run something like that for ten hours, you'd need something rated for 35 amp-hours. If anyone else on this group wants to correct my math, they're more than welcome.
One of the cool things about LEDs is that they're just that - cool. So you can probably put as many as you can fit into a film canister and not have a heat problem. I'd just mock one up and try it overnight.
Are you using transformers for this project? If your LEDs are rated at 3.6 and 4.5 volts, it's probably not okay to run them at 12. -
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Re: Burning Man Project with 360 Leds NEED HELP PRONTO
Tue, August 15, 2006 - 9:36 AMI am just using resistors. How would you wire up transformers to leds? This web site has some pretty interesting info on wiring LEDS www.quickar.com/ledbasics.htm snd this is the site that gave me the idea to wire in series parellel, but I just don't know if this is what I should do because I hear bad things about each way of wiring. -
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Re: Burning Man Project with 360 Leds NEED HELP PRONTO
Tue, August 15, 2006 - 10:29 PMSo I'm more of a high-voltage guy, but...
From reading that site, I think I understand what you mean by "series parallel." They describe wiring the LEDs in an array in which groups of LEDs wired in series are wired in parallel. They suggest this to avoid raising the voltage or ampiere requirements to ridiculous levels, and to save on componentry.
If you wire using strings that raise the power requirement to just short of 12V, the resistor would be a practical way to adjust the voltage for the strings of LEDs. Then you'd put the strings in parallel until you got them all wired. If you were using a transformer, you'd just put it in the circuit between the battery and the LEDs. But on reading the site you link to, transformers seem like unnecessary complication.
The matrix method (it's the example near the bottom of the page using 12 LEDs) seems to me to be the most efficient way to power all those LEDs. Just add strings of LEDs until you reach the number you want. The only part that should produce heat is the resistor. So if you're worried about producing too much heat, put the resistors outside the film canisters.
I think the resistors will increase the total load some, so a string of three LEDs will draw more than 90 mA at 12V. I would just make one of these strings, hook it up to a 12V battery, and use a multi-meter to find out the draw in amps. Then multiply that by the number of strings in your system. That'll give you the total draw in amps. Multiply by ten, and you know how many amp-hours your battery will need to give you. Give yourself some wiggle room. The wire has resistance too. -
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Re: Burning Man Project with 360 Leds NEED HELP PRONTO
Wed, August 16, 2006 - 9:40 AMThanks I think all this has helped me out alot. -
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Re: Burning Man Project with 360 Leds NEED HELP PRONTO
Wed, August 16, 2006 - 1:59 PMAwesome. Post some shots when you get it working - whatever this is sounds pretty cool.
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Re: Burning Man Project with 360 Leds NEED HELP PRONTO
Wed, April 4, 2007 - 6:29 PMHi Clint, did this project get going for ya ? I'm very curious to see the outcome!
Good luck!
Albie
