Anonymous says:

I would use a 1000-ohm resistor in series with the LED you can go down to 650 ohm if you want it be brighter. The key issue here is to keep the CURRENT level below the rating listed on the LED. I run mine at half the current rating and then they will last a very, very, long time. You can series them together but again the current rating must NEVER be exceeded. If you have 12v of power and the LED are 2v each you will need 6 LED in series or more to get the LED to be rated at 12v of power output of the supply voltage. at that point you will have to add LED’s or resistors to get the current down to a acceptable level. There is one other option and that is go get a Radio Shack variable voltage adjustable regulator it will cost you about $5 plus parts to build and you could run up to 30 LED’s at15 milliamps each.——AlanC.