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What is the safest (and most reliable) way to power a dozen LED's burried in a floor? Answered

I know sculpting and carving, not circiuts! I've added some custom glass etchings to the tile floor in a bathroom that are lit with LED's embedded under the Travertine and Grout. There are about a dozen 3v White LED's spread throughout the floor and all wired in parrallel. They are hard to change. Once they burn out, they most likely won't be dug up and chaged, so I want them to last as long as possible. In my previous installation, I simply used a 3v battery pack inside the closet with a wall switch in the entry to control the circuit. In my current floor, I've also used a battery pack to test them and am now ready to build a permanent solution. This time (thinking ahead) I have built a switched outlet in a wall cavity that will provide power to my floor lighting. The question is this: What is the best way to power them making use of the switched outlet? My original idea was to simply buy a 3v wall wart power supply typically rated at between 750 and 1000ma at the switched outlet. The reason I'm asking you fine folks about this is that Im concerned about providing too much amperage to the lights and burning them out (if that's possible). Once they're gone, theyre gone. It is not very practical to dig them out. Is this a good idea? There is nothing else in the circuit but the 3v LEDs and the power supply (no resistors, etc). My backup idea is to use a 120v relay and a battery pack at the switched outlet. This seems the safer solution (less chance of burning out the LED's), but would require changing the batteries once in a while (probably every couple years with typical usage.

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user
Padlock (author)2009-07-14

If you have them wired into the floor WITH a resistor, than you could have a wall-wart that gave you 100 amps - it wouldn't matter, because they only use as much electricity as they need (The resistor would limit the flow.). If they do not have a resistor, I highly recommend installing one- check Lemonie's post for a link to calculate the value.

As for a different solution, maybe buy a rectifier and power the LEDs directly off 120 VAC (Make sure it's safe, a.k.a none of the electrodes are extremely close. Unless they're sealed in grout.) Just use the link mentioned above, and for source voltage use 170 volts (120 * root(2)). If you add smoothing capacitors, however, it would just be 120.

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user
Padlock (author)Padlock2009-07-14

Also, when calculating your resistor if you choose to do so, pay special attention to the power dissipated by the resistor. Make sure to buy an appropriately rated one.

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lemonie (author)2009-07-10

Use this calculator and see if it gives you any help / ideas:
http://led.linear1.org/led.wiz

L

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