This is the first flashlight that I've actually built into a regular flashlight body. It didn't start out that way though. When my white LED's arrived from BG Micro I realized that I needed some kind of reflector for them. First off these dont appear to be the latest bright whites. They are plenty bright for a very nice flashlight, but they are only rated at 20ma and I think the latest ones are rated at 30ma, and are also more expensive. For the next project I'm going to get some of the $3 a piece ones and see how much brighter those are. So I ordered some individual LED reflectors from Fiber Optic Products
Since I was originally planning to build this into another DV Video case even smaller than the last one I was planning to use a 3AAA battery case that fit nicely inside the case. Running NiMH rechargeables that would give me almost exactly the right voltage for the white LED's, so I planned to just connect them all up in parallel, but that turned out to be not the best way to do things. 5 LEDs in those reflectors would fit across the case. So I lined up 5 reflectors on a piece of tape and started soldering the LED's in parallel. I put a piece of stiff wire along each side and tied a knot around it and the LED post with some wire wrap wire and then soldered and trimmed everything down.
It actually lit pretty good, but pulled a lot of power and once I connected up a little dimmer circuit it just didn't light to full power from those batteries.
and inside of the DV case
Further study has gleaned that most people recommend against running the LEDs in parallel because they are not all made exactly the same and some will have slightly different voltage drops which can lead to very different light output across the array. I did see a slight variation in their output, but only when they were dimmed down a lot. I must have got lucky with this batch. Wired in series they even out the voltage across them, but require a higher voltage.
I built a VERY simple dimmer circuit by simplifying even further the first schematic on ODDONE's White Led page. You can buy all the parts at Radio Shack and when dimmed all the way off the current is un measurable on my multi meter. Less than one micro amp. So no switch beyond the pot is necessary. Just dim to off.
But since they didn't come on bright enough through the dimmer circuit I had to have a higher voltage power supply and opted for a 9v battery in this case. I'm using a NiMH rechargeable in it now and it's working great. But that battery just wouldn't fit inside the DV case, it's too wide and the case would not shut. So I dug around until I found a very old Duracell Durabeam flashlight.
I spray painted the case with a white epoxy enamel and then a matt finish to make it easier to hold on to. The bezel is rectangular and would fit 6 of the LED reflectors with only a little bit of sanding on the edges to get them to fit close together. There is a lot of room inside this light to hold the 9v and the dimmer and anything else you might want to add.
The nasty looking knob glued on the top is the dimmer pot. Eventually I'll attach a decent looking knob over it to hide the glue and connections there. This was the only way to mount it without cutting into the case.
The beam is actually very nice and round even though it's coming from 6 separate LEDs. They are wired in 3 parallel sets of 2 wired in series with a 47 ohm resister for each series pair. At full power they pull just over 30ma each, so they are overdirven somewhat from the spec of 20ma but I've run them like that for extended periods and they dont even get warm so I'm not worried about them.
The light is very bright! I'm very happy with the way it's turned out. The beam has a nice hot spot while still spilling enough to light a whole room. I haven't done any runtime testing yet, but a 9v doesn't hold a whole lot of power so it probably will not last more than a few hours at full power. But with a rechargeable in there I don't mind.