LED motorcycle tail-light

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Joined Apr 6, 2009
  • I have recently fabricated a custom LED taillight for my bike using flashlight guts. My problem is that the LEDs burn out quickly. I think I have to regulate the voltage to the LEDs but have no idea how to go about it. Any ideas would be much appreciated.​
  • Bike: 1974 Honda mt125​
  • Batt. Volt: +/- 6Vdc​
  • LED units designed for three AAA batteries (4.5Vdc)​


Joined Apr 6, 2009
Check out the 7805 regulators, or the LM317 adjustable regulators. Limit the current with a fuse or appropriate resistor. Good luck.


Joined Aug 7, 2008
Do you know how the LEDs are arranged, or what the current draw for the unit is? You only have 1.5-2.5V to play with, which might not be enough for IC reg. Might just need a resistor, and maybe a 5V zener diode for protection.


Joined Jul 17, 2007
Actually, you need two different levels of current supplied to your LEDs; one level for "running light", and one level for "brake light".

I think the original light for that bike was an 1157 type bulb with twin elements; a bayonet-base bulb with two connections at the base, one for park/running lights and the other for brake.

I suggest that the first step to take is to get a new bulb, and three new "AAA" alkaline batteries, and measure the current flow in the circuit.

Once you have the current flow, we have something to work with (the maximum current).
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