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Looking to play around with the CREE Xlamp series LED and was wondering what would I need to drive them off 110V household power?

Output current needs to be in the range of 800-900mA.

EDIT: I am looking to do this for creating lighting for a NanoReef tank. I would be combining several of these in series.

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As was suggested twice already you do not want to power this directly from the line. You should have an isolated low voltage supply.

I would use a current-sink to provide a regulated current. An easy way to make a current-sink is to use an op-amp, resistor and FET. I have been working on a prototype that is four channels at 20A per channel. For an LED application the practical limits would be around 2A per channel (due to cooling). A picture of my prototype that is powering 5 1W LEDs is at http://tinyurl.com/yzg9kd7

I have mounted the LEDs on a heatsink. I use thermal grease between the LEDs and heatsink. I have a schematic of a current-sink (a.k.a. load cell) at http://tinyurl.com/6cbn6h (scroll down to the "Electronic Load" section.

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I would not advise driving the led directly with household voltage - it is far too high for this low voltage device. A further consideration is that the led requires DC to drive it and the household power is AC.

These LEDs will draw 800-900mA at a forward voltage of around 3.2 v. If you use a wall wart (plug and voltage regulator all in one) with an output of 5v DC (a common value) then a 1.8 ohm 2 watt (or greater wattage) resistor in series with the led would do the trick. Note the led will need a heatsink as it will need to dissipate about 3W.

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  • \$\begingroup\$ Good point. On another note: LED replacement bulbs then have the voltage regulator and load resister built in to the housing? \$\endgroup\$
    – jdiaz
    Dec 22, 2009 at 19:37
  • \$\begingroup\$ Edited original question to include more info. \$\endgroup\$
    – jdiaz
    Dec 22, 2009 at 19:47
  • \$\begingroup\$ Yes - led mains voltage bulbs need a rectifier and voltage regulator, they are contained in the bulb package. \$\endgroup\$
    – JohnC
    Dec 22, 2009 at 20:34
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At that power I'd use some kind of switching regulator for efficiency.

I wouldn't dare to go directly from household power to the LED without a lot more research. For a start I'd rather use some wall wart to provide say 12V and step that down to the LED.

Also, make sure to cool them sufficiently.

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