Hey, My mum is doing an exhibition, part of which requires her to light up some cardboard-cutout "windows" covered with what is basically OHP-transparency type material, printed on with stained-glass designs. She doesn't have the faintest clue how to light them up simply, and she can't have wires trailing all over the place, so turning to me I suggested LEDs. I was looking at getting hold of a few of these, but I wouldn't be able to run wires, let alone a PSU to it. Here's where you guys come in. Is there some way that I could rig those beauties up to run off batteries, hopefully commonly-available ones? Or, do any of you have any better ideas re lighting for her exhibition? The lights would have to run for as long as possible (hence LEDs), but the whole thing goes for about three weeks. Oh, and she wouldn't have much use for the LEDs after, so if they were usable with Molex plugs afterwards it would be nice Cheers
im sure u could run them off batteries but they would have to make it up to 12v of course. Also i dont know how long the batteries would last
Don't LEDs usually run off 5V? Also, looking harder at that thing, it's not a LazerLED cluster, it's just three LEDs in serial. It would most likely be easier to buy LEDs and resistors, but I'd still have to set up a decent circuit. Help
Dunno what it is, says inverter-powered. What size are these windows? For even illumination on a decent size, a white CCFL would be far better than leds. Could run it off a 12v car battery, swap & re-charge every few days.
Those leds would run off 12v if u wanted it connected at the molex. It would have its own built resistor/s to bring down the voltage (u said u wanted to keep the molex if possible).I second a white ccfl
And there would be so much potential for the cathodes afterwards! The problem with the cathode idea is a) the price of cathodes and inverters; b) the price of a couple of decent car batteries; and c) where to hide the damn thing. Oh, what sort of wattage would I get out of one? Plenty to power 5 CCFLs, but I'm interested anyway
Well, I'd say it would be easiest and cheapest to buy some white LEDs. Most of them run off 5V, easily obtainable using batteries. 4 AAs will give you 6V and just need to shove a resistor in there. Now say your average bright white LED pulls 30mA of current at 5V. For the sake of this imagine the batteries are putting out 5V together. Duracell AA batteries contain about 2200mAH (milliamp hours) of charge, which means you'll get 2200 hours at 1mA. So we divide 2200 by 30 which gives just over 73 hours continuous running of an LED from 4 AA batteries. I don't know how long this exhibition will be on for but it might be best to use Ni-MH batteries instead. They can hold less charge but if it's up for a few days you could easily get a full 24 hour day from each set and replace them with some freshly charged ones. I don't know if it'd be a bit expensive to do since I'm not sure of the amount of light you need putting out. Just remember if you use 2 LEDs then the time will half. If you connected a second set of 4 AA batteries in parallel with the first you'd get double the amount of power to play with but still have the same voltage. Hope that was of help. PS. If you could hide away an old PC PSU in there u could use that for power
A 12 volt car battery will run a white CCFL for weeks. If you think about it, the systems in your car draw at least 100mA combined when the ignition's turned off, and the battery copes then. (Assuming you have a newer car of course).
Ok IMHO LEDs will be the easiest way - I'd use 5000 mcd whites running a LOT dimmer - you should get enough light if leds run down as low as 10ma or less I'd wire them from 4 rechargeable nimh batteries - 2000 mah. so one led would run for 66 to 200+ hours . Would be handy to know what size the windows are (all the same size?.) I can get some clip on lenses that diffuse the led light and also would use cheap mini pots - ie wire LEDs so the they run at 28-30ma if pot is set at zero ohms and turning pot dims light - taht way its easy to dim light to an acceptable level to find balance between brightness and battery life? CCFLs would give a better light - but expensive (though I can get cheap ones via USA - but an 12v inverter uses 300+ma - never metred the 5V ones.. Basically if ya wanna e-mail me I will help with cheap supplies etc.. When is the exhibition?
Thesedays a 5V led is rare - mine are 3.3V on the whole - blue,UV,white etc. Reds and Oranges at 1.7V.. As another thought - it would be easy to make backing lightboxes from white card?
Personally I'd try to avoid using any kind of resistor. When we're trying to prolong battery life you don't really want any wasted energy. I'd be tempted to use some kind of charge pump, or flash the LED's at a few hundred Hz to extend battery life. A CMOS device (4047?) would be ideal since they use very little power themselves.
i have some LEDs that are 8000mcd... they run at 5 volts... uses 9-10ma... remember: if a LED (led itself with no resistor) needs high voltage it normally uses less current...
