Picture of £1 Poundland Übertorch (3 D-cell 25 LED torch conversion)
I've been looking for an opportunity to carry out an LED torch conversion for a while, but the criteria for finding a 'donor' torch were fairly stringent. It needed to be:

- inexpensive
- capable of powering white LEDs (so containing a power source generating over 3.6V)
- actually, very inexpensive (in case I made a catastrophic error during the build and broke it)

The benefits of an LED torch over an incandescent one are simple - with the 'high brightness' 20 candle-power white LEDs it's now possible to buy on eBay (I bought fifty for 9GBP), a great deal of light can be produced, and significantly less current is drawn, so the batteries last a lot longer.

I was really pleased, therefore, to find a donor torch in a shop called 'Poundland' for just one UK pound (hence the name!) - it takes three D cells, which generates 4.5V - plenty to drive an array of LEDs.

Here's a list of things that are needed for the project:
- a cheap 4.5V 3xD cell torch (eg. from Poundland)
- 3 1.5V (so not rechargeable!) D cells.
- a 13x13 piece of 0.1" pitch copper-clad stripboard (like "Veroboard")
- 25 high brightness white LEDs (like these: http://is.gd/2Gaa0 - eBay link)
- 25 47ohm 0.25watt resistors (or whatever's appropriate - there's a handy parallel array calculator here: http://led.linear1.org/led.wiz into which you can type the specifications of the LEDs you buy to get the correct value)
- 8cm of small insulated wire
- plastic packing ribbon
- resin adhesive (two-part if available)
- insulating tape
- blu-tak or equivalent (it's not a proper project if it doesn't involve blu-tak!)
- a couple of small screws

Tools required:
- a soldering iron and solder
- a drill or bradawl
- wirecutters
- needle-nose pliers for bending
- a craft knife
- a hacksaw to trim the board down.
siamonsez3 years ago
The ebay link is no longer valid, does anyone know a place online to get the leds and resistors?
markvid6 years ago
Nice instructuble, I'd like to make something similar myself. But I think it's better to wire some LEDs in series, instead of having all of them in parallel and needing resistors, which is a waste of energy. But in your case you would need more than 4.5V