Convert a dive light into LED

This is not really physics stuff. Well, it could be, but I am not going to take it that way. This is just a post that I consider to possibly add to the usefulness of the internet. When ever I want to do something, I always search online first. Suppose I want to make one of my dive lights into an led - if someone has done it that will help.

So, I am super pumped up. I am getting ready to dive the Oriskany (off the coast of Pensacola) soon with some of my old dive buddies. Will I need a light? You bet. Do I think led lights are awesome? Oh, yeah. Do I want to spend tons of money on a new dive light? Ummm...no, I am way too cheap. Here is my conversion of a normal scuba diving light into an LED light.

For this conversion, I am starting with an Underwater Kinetics SL4 dive light. It has a normal incandescent bulb and runs on 4 C-cell batteries. I am also going to use (but not destroy) this awesome $15 TaskForce led light I purchased at Lowes. Indeed a bargain, it is a great light (I think I might pick up another one). There are a couple of other things I used, but I found them around my house.

Here are the two light housings from the lights. You can see that they are of similar size, but the SL4 has a larger diameter. This TaskForce light is awesome because inside the light housing is the led driver circuit, all in one package.

Let me look at the SL4. Here is where the light housing goes.

The arrow points to the important part. This little metal thingy makes electrical contact with the light housing. The led light (as it is) won't make contact due to its size. If only I could find some metal to put around the led light so that it becomes a similar shape. Check this out.

If you have an old 10 or 20 GB hard drive laying around. You should definitely take it apart. I mean, what good is a 20 GB drive these days? You can get a 1 TB drive for like $100. Oh, and the platters make awesome mirrors (except for the hole in the middle). Anyway, there are these aluminum rings that keep the platters apart. They are the PERFECT size for my light. (you will need a torx screwdriver to get these out). I actually had to use the rings from 2 hard drives. I could have just used one, but I would have had to glue or solder it to the light. I didn't want to do that because after the dive I would like to use the TaskForce holder again.

Here are the two light heads side by side with the modified led head.

There is still one problem. The TaskForce light runs on 3 AAA batteries and the SL4 runs on 4 C-cell batteries. I can take out one of the c-cells, but then I need a dummy battery to make the light work. I looked around for something of appropriate size, but ended up building my own.

This is a PVC pipe with pennies on each end. I have a wire in the middle connecting the two pennies. Also, I put a screw through one of the pennies so that it would have a 'bump' like a normal c-cell. This is a shot before I added some stuff inside to increase the density and before I glued the pennies down. The density is important because you don't want a flashlight that is very floaty (that is a technical scuba term).

The last step is to turn the batteries around. The battery orientation on the SL4 is opposite of that for the TaskForce light. For an incandescent, this doesn't matter, but it does matter for an led light. After that, done.