Mag-Lite Solitaire led mod

Hi everyone, I finally decided to join this forum after coming across it many times.

My goal for this project was to convert the Solitaire light to led, and to make it as bright as possible.
All the parts used were what I had on hand except for the A23 batteries. I used a half watt led salvaged from another light and mad a simple constant current circuit to drive it. I also used lenses from an old camera I dissembled to help focus the light.
The current draw is about 70ma to drive the LED at 65ma. (ish) The light should run until the battery voltage drops to about 4volts but only time will tell. I decided to go with a buck driver because I don't really know how to make a boost converter without an IC to deliver the current needed. Hopefully the time I spend here will help with that.


Here you can see the setup as it will be inside the light. The tail cap has been drilled to accommodate a tactile push button switch. (That was a challenge)



These first two pictures show the light with the two lens combination for better throw. (10ft)



And these two pictures show the single lens for a flood light effect. (10ft)


And here is the finished product, all in all I think it turned out well. Tell me what you guys think.

Very nice!

Nice first mod! I started with sticking a 5mm LED into a minimag.

There is a 10440 Li-ion battery that can be used to direct drive a high power LED. I'd read up on battery safety first before buying those batteries though, since they don't have a protection circuit.

:welcome:

Thanks guys, and I will look into those lithium batteries for sure.

Very nice!

Nice first mod Josh101 and welcome to CPF.:thumbsup:

Do you mind sharing which switch you used and where to find them. I have always had a hard time finding a switch that small that would fit. A pic of the switch would also be nice. Thanks for sharing.

I used these tactile switches from radio shack. There 6mm X 6mm.
To get it to fit I had to sand down the corners carefully as to not damage the leads, and drill out the back cap for it to fit. I don't have a picture of the switch installed because it's encased in hot glue. This part was probably the hardest part of the build.

Model# 275-003 ?
Did you shorten the button any or use it as is? Looks almost flush in the pics.

Yes it was a pack of 4. No I didn't shorten them, the switch has a short travel so it's practically flush. Try mouser electronics, they might have a better switch.

There are also some 6mm x 6mm latching switched on eBay if you want constant on.

A simple boost converter to make is the Joule thief (there are many sites that show the circuit). If you make it out of SMD components and a small coupled inductor, they can be made pretty small. SMD components can be hard to solder though.

I have made a joule thief before, but never with SMD components. I will have to try, but do you know how to increase the current from the joule thief? The most I ever got was around 30ma.

I've been trying to figure that out too. You can increase current by decreasing the resistance to the base of the BJT, but don't drop the resistance too low. I didn't measure the current out vs resistance, so I'm not sure how much the current can be increased.

A bigger inductor should also store more energy, but I'm not sure how much more power that pushes (should probably use a scope and see).

Diodes inc has some small IC boost drivers that are pretty easy to wire up. They don't run as low as a joule thief voltage wise, but they do work pretty well:
http://www.diodes.com/products/catalog/list.php?parent-id=92

I was able to get a Jfet joule thief to run down to 200 mV before the LED went out. It wasn't very bright, but it made enough light for reading my desk clock. I was drawing ~3-4 mA at that voltage, so probably a few hundred µA to the LED.

If you want to look more into DC/DC converters, I found this to be an interesting read:
http://www.maximintegrated.com/app-notes/index.mvp/id/2031

I just ordered some of those Diode inc IC's actually, the ZXSC380FHTA. It can deliver 75ma at 3v max.
Nice job on getting that joule thief to run so low, and thanks for all the help.
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