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These articles first appeared in Audax UK's hardcopy magazine, Arrivee, and have been only slightly adapted for the web.
Please read them in the context of their original publication date, as prices, specifications, weblinks and even opinions will change over time.

Upgrade an LED light by Francis Cooke
A slightly adapted reprint of the article first published in Arrivee, December 1995

I've had a few requests to reproduce my article about upgrading a front LED light, which was first published in the 1995 Calendar edition of Arrivee Extra. So, if the Editor can find space, here it is. The instructions refer specifically to the 'KnightLite' 5-LED light, which is particularly easy to work on. Other lights can be upgraded in a similar way but may well be more fiddly.

The 'KnightLite' 5-LED is a neat and well-made light, with several modes of operation - personally I think the faster of the two flashing modes is the most visible of all, but it's good to have a steady mode available at the touch of a button. Best of all, it's very easy to disassemble, to substitute the latest and brightest LEDs into the circuit. The rear light hardly needs this treatment - it's one of the brightest on the market already - but the front light can be transformed using LEDs which are over 30x brighter than the originals. It's a fiddly one-hour job.

The KnightLite is also available as Halfords' own brand - this is the 5-LED oval-shaped light, not the newer 1-LED BS-approved light which is also badged as both brands. The mounting arrangements on the Halfords version are different - I prefer the original mounting but otherwise the lights are identical.

Here's how to upgrade a front 'KnightLite'. You need: small flat-blade and cross-head screwdrivers, thin-nosed pliers and end-cutters, a low- or medium-wattage soldering iron, and a magnifying glass. A de-soldering tool would be useful but not essential (I don't have one), and a couple of bits of wire for testing the LEDs before re-assembly would also be handy.

And you need the latest brightest substitute 5mm LEDs. As I write, these are, for the front, Toshiba TLYH180P, available as Farnell part no. 623-738 for 90p each. These are a searingly bright deep yellow and very directional. The attached panel shows some other very useful LEDs that you could use for front or rear upgrades - all except the new white ones are electrically interchangable with the ones you will find in any LED light so can be used as described below.

Open the light and remove the batteries. Remove the three small cross-head screws, two to the right of the row of LEDs and one near the left-most LED and put these and the metal battery-clip that has come loose to one side. Gently prise up the strip of circuit-board on which the LEDs are mounted (not the thin silver reflector, the thicker board underneath). This comes free, attached only by two thin wires. Remove the small (but vital) black plastic moulding at the '2-screws' end and put it aside.

De-solder the two thin wires, noting that the red wire (+ve) attaches to the terminal nearest the end. The 5 LEDs are now freed and isolated from the rest of the circuitry.

You can replace any or all of these LEDs - you could just replace 3 for example to get a colour mix. Cut the old LEDs out with the wire-cutters - when the leads are free they just push out backwards. Clean up the solder-pads by holding the board upside-down and applying the soldering-iron from below, then use the magnifying-glass to check you have not created any short-circuits.

Now it gets ticklish. Peer inside the old LEDs and you will see two electrodes, one big and one small. The small one is the +ve. Find the +ve on the replacements and bend the leads at right-angles in the same way as on the old LEDs. This can be tricky as they are quite delicate - use the thin-nosed pliers to start a bend as near as possible to the body of the LED, then push it down flat by hand. Remember there's not going to be much room when all this is put back together!

'Tin' the leads on the new LEDs. This needs care too, as LEDs can easily be destroyed by a hot soldering iron. Just dab some solder on the tip of the iron, then run it quickly along the 1cm of lead nearest the bend.

Push an LED into place and solder the leads back onto the pads. Repeat with the others. Push all five into a nice straight line, all pointing the same way. Soften the solder again if necessary.

Check for short-circuits again, then check everything works, using your bits of wire to connect any 3V source (you could use the batteries supplied, fitted back in the shell) to any pair of 'legs' - the LEDs should all light. Wrong polarity won't matter, but even so, make this a brief check - don't keep the power connected for more than a second or two or you may damage the LEDs.

Reassemble - trim all the legs back neatly. Resolder the thin red and black wires to their pads, red nearest the end. Replace small (but vital) black plastic moulding and then screw LED strip back into place, not forgetting the metal battery clip. Make sure the strip is nice and level. Clean up any fingermarks. Batteries in, cover on.

Guaranteed - this light will now earn maximum respect from every oncoming road user!

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