Info

Total Cost

£75.52

$113.10

beneath the resist, and the board can then be drilled to take the components.

Putting it Together

The resistors (available from any electronics store) were soldered into the board first. This minimised the heat to the LEDs, which were held in a small forceps used as a heatsink during their installation. As can be seen on the component overlay (enlarged to show details), a small length of wire on the component side of the board is soldered from the inner positive connection to the outer ring to complete the circuit to the outer LEDs.

Connecting the assembly to the Mag-Lite couldn't be simpler. The standard torch bulb is held in with a very robust screw collar. To make the connection to the torch, I simply broke the glass out of an old bulb, and soldered the two thin flexible wires from the PC board into the metal bulb base (first passing them through the reflector and screw collar). The base of the bulb is the positive supply, and the torch body the negative.

The torch doesn't have to be modified in any way whatsoever. The PC board sits in the reflector, and the LEDs just press against the plastic top of the torch. You can do this conversion on any flashlight designed to run on 4.5 volts, providing that the reflector housing is large enough to accommodate the PC board and the LEDs.

Results

The finished product is fantastic! It doesn't give a 100 yard pencil beam, of course, but that wasn't the point. The flashlight gives a very even spread of white light that is easily bright enough to illuminate a room or tent, or to light your way over the roughest of terrain.

I chose to optimise the LEDs for maximum light output, not being overly concerned with battery life. Higher value

Easy access to the reflector and connections made the conversion simple.

Easy access to the reflector and connections made the conversion simple.

resistances could have been used to reduce current drain, giving longer battery life. But this would have been at the expense of the light output.

Reliability and occasional use were the main requirements. Overall current consumption at around 220 mA may seem a little high, but nowhere near as much as the standard three-cell bulb at 750 mA. These LEDs are very efficient. Even when NiCds supplying only 3.6 volts are used, they will produce high levels of light, while reducing the current drain to 10 mA for each LED.

My total cost was around UK£55 (US$75). Expensive, yes, but still about UK£15 (US$23) less than buying the CC Expedition Flashlight in the UK. And I ended up with a torch with eleven LEDs rather than seven!

I was lucky enough to buy a twin pack containing a three C-cell Mag-Lite and a mini AAA Mag-Lite at the local wholesale warehouse for a total price of UK£19 (US$30). The mini AAA Mag-Lite is destined to have a single white LED * fitted to run from one AAA cell via a single transistor inverter, but that's another story!

The bonus of using solid state lights is their long life—at least 100,000 hours is expected. They also give a constant colour as the voltage of the battery drops, yet they still give a very useable light source.

The converted torch has been running for several weeks now, and after many hours of use, I've seen no noticeable drop in brightness. I took it on the first camping weekend of the season, arriving at the site by motorcycle just after dusk. The even spread of light made it ideal to use while I set up my tent. It also provided a really good interior light, easily bright enough to read by, even when reflected from the roof of the tent.

Comparison test: Stock Mag-Lite on left;

My flashlight conversion has generated lots of interest from friends who've seen it. Many of them want to have a go at their own conversion, so it looks like I'll be etching a few more PC boards before long!

Access

Peter Jones, 2 Highcliffe Dr., Sheffield, England S11 7LU, UK • 44 114 230 3704 • [email protected]

Farnell, International Distribution Centre, Castelton Rd., Leeds LS12 2EN, UK • 44 113 263 6311

Jones'converted LED Mag-Lite on right.

Fax: 44 113 263 3411 • www.farnell.co.uk LEDs, #993864, Nspw500, 5 mm white

Maplin Electronics, National Distribution Centre, Valley Road, Wombwell, Barnsley, South Yorks S73 0BS, UK 0870 264 6000 • Fax : 0870 264 6001 [email protected]www.maplin.co.uk Printed circuit board, photo-resist, and developer got solar?...we do!

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