I have an old halogen Undwerwater Kinetics SL6 (six C batteries) that
I thought would be nice if I could convert to LED. I will probably be picking
up a new LED light eventually but thought the SL6 is not super portable but
better than my UK C8 lite. If it's a big deal to change to LED will probably
just leave the SL6 as back up. They do get around 100 bucks for the UK C4
LED which I am considering as well. I know the LED's run a bit warmer but was
thinking maybe a 200 lumens LED would be great if it could be used in the old
SL6 Halogen light housing.
The conversion can go from not to hard to fairly complex depending on what you want to accomplish. The biggest electrical problem most people run into when it comes to converting a light to LED is how to match what the LED wants for voltage and current to what you have. The biggest mechanical would be how to mount the new circuitry in the old housing, so that it is both secure and placed properly inside the reflector.
Matching the current and voltage requirements can be done using a resistor to limit the current through the LED and letting the intrinsic voltage of the LED handle the rest. Simply look at what the data sheet of the LED and figure out what it's forward voltage and operating current are, then measure the voltage at the terminals of your light when it's switched on. The value of resistance you will require is:
(Vlight - Vled)/Iled = Resistance
Upside to this is that it's simple and cheap resistors run in the order of pennies. Downside is that basically you'll be throwing battery life away in the form of heat through the resistor.
A better way to do this is to use a switch mode power supply (SMPS). Again start at the data sheet of the LED and determine the same as above, then build accordingly. This is by far the most complex way BUT the good news is there are ALLOT of hobby sites out there that have the power supplies already designed and built for the majority of lights. If you search deal extreme for flashlight parts you can purchase power supplies for ~$2.00 (
Cheap Led Driver Circuit Boards for Flashlights at Dealextreme - DX)
The second method is much more robust as the SMPS will keep it's output steady in both current and voltage regardless (assuming you don't over voltage it) of the input voltage until the battery is dead.
All this being said the purchase price of $50 for a drop in module is more then fair for saving you the hassle of trying to devise a mounting system.
Best of luck
