This describes how I made my own LED bicycle lamps, inspired by the attempt of Fisha
Thanks to the 2 locosters who made the 5 mm aluminium discs and sent me small sheets of polycarbonate for the lens covers - you know who you are!!
As my Smart twin halogen lamps were ageing – plastic lenses getting more scratched as well as the silvering deteriorating, I needed to find a replacement. My options were to buy another set of Smart lamps, Halogen, HID lamps or LED lamps. I decided on LED lamps as these do not use bulbs and are the most efficient.
The down side is their cost and since I did not want to pay upwards of £ 150 for lamps, I decided to make my own.
The Fisha design ™ uses an aluminium box to house the lamps but I wanted something more compact and cheaper. The hardest part was making the lamp bodies. These are made from 2 different diameters of domestic heating copper tube, 22 mm and 28 mm plus one 22 mm coupler outer diameter 24 mm). A “thimble” was made by cutting a disc from a piece of flattened copper pipe with tabs and then folding the tab over a socket.
This can be seen on the far right, the pipe joiner in the middle and the larger diameter pipe top left. The “thimble” is fitted over the coupler and is a snug fit inside the 28 mm pipe – seems like the pipe wall thickness is 1 mm. There are two pairs of 2 mm holes, one set for bolting the LED emitter and the other for wires to the emitter. M2 screws were used as their heads are small enough not to touch the pads on the emitter. Larger size bolts could be used but would require insulating washers. After cleaning the metal, the copper tubing is soldered together with plumbers solder to make the lamp housing.
The emitter needs a lens to focus the light. One lamp has a 6° lens and the other a 15° lens each held in a lens holder. A clear polycarbonate disc fits over the lens and glued into the pipe with 2-part epoxy to hopefully make the lamp waterproof.
It so happens that the pipe coupler, outside diameter 24 mm, is the correct diameter for the handlebar clamps.
The lamp housing gets very warm when driving the LED emitters with the 5 W driver, I measured 49 C inside the lamps which although is within specification, is not ideal for the drivers. I later added an heatsink made from a disc of thick aluminium between the “thimble” and emitter as well as a short length of copper tube fitted inside the lamp. The lamps were painted matt black to maximise heat dissipation.
On my first test ride I could barely feel the lamps being warm so my concerns about overheating may be unfounded, admittedly the air temperature was around 2 C but hopefully the air flow will be sufficient to keep them cool.
When stationary, it seems the temperature rise is around 30 or so degrees above ambient so best to keep moving.
With hindsight, I could have fitted both drivers inside the switch box.
Initially I used 3 W drivers purchased on ebay, China which were later replaced by more powerful 5 W drivers, again from ebay with the added benefit of being on a smaller circuit board. Both boards will fit inside the 22 mm pipe coupler. Photo below shows both drivers, the 5 W driver is on the left above the 20 pence piece.
The two wires to the LED emitter were cut to length and stripped with two thinner wires soldered onto the ends. These were used to pull the wires through the holes in the “thimble”. The thin wires were then unsoldered before the wires from the driver soldered to the emitter’s pads – a fiddly process.
Photo below shows the emitter bolted down and wired up to the 3 W driver. The lens and lens holder are not fitted.
Finally the driver broad was sealed in 16 mm heatshrink tubing to insulate it from the copper pipe.
The drivers supply a constant current to the LED emitter and will work from a range of voltages, I am using 7.2 V NiMH 3800 mAH battery. The current drawn by the 5 W driver is around 1.4 A which gives a theoretical run time of 2.7 hours or 1.3 hours for 2 lamps.
The rear of the lamp is sealed by an aluminium disc. Initially I planned to fit a switch to the rear of the lamp but had difficult finding twin core cable of a small enough diameter to fit next to the switch, most cable being figure-of-8 which would have made sealing the lamps more difficult.
In the end I made a switch box to fit onto the handlebar stem made from a 9 V battery holder with the innards removed - the smallest plastic case I could find sold in Maplins.
The switch box has 2 power sockets for the lamps. I could have saved a bit of money by not fitting plugs and sockets but I wanted to make the lamps removable. The hole in the battery box cover left after removing the switch was covered by insulation tape (not shown in photo).
To make it easier to remove the battery from the bike for charging, the cable to the switch box is terminated with the RC type connector.
The switch box is held on by a Velcro strap and a strip of rubber with slots cut for the strap and for the switches – time will tell how robust this is.
Possible future enhancement would be to use more robust mounts – the ones used are two part held together by a tiny screw to allow the side to side movement, very likely this screw will loosen. Also very little effort is needed to pull the plugs out of the socket, I may have bought the wrong ones but there is enough tension in the cable to force the plugs in. They did not come loose on the trial ride.
Should the lamps run at a too high a temperature, the next version would be mounted on a length of 25 mm diameter aluminium rod but I haven’t figure out how to make the wiring neat.
Both drivers, 3 W and 5 W have a pin to modulate the output - I cold make a PIC to control the brightness so do away with one of the switches.
Parts required to make lamps.
Someone help me format this table!!!
Item Source Part number Price
Lamp body made from 28 mm and 22 mm copper tube and coupler for 22 mm tube A 26 mm diameter 5 mm thick aluminium disc for a heatsink. available from B&Q
M2 screw, nut, washer and internal shakeproof washer to bolt down emitter RS components but sold in bags of 100
Also on ebay
Seoul P4's white star emitter http://www.dotlight.de
these have now appeared on ebay products_id/909 6.98 €
Lenses Spot Beam 6° http://www.dotlight.de
products_id/473 1.84 €
Lenses Spot Beam 15° http://www.dotlight.de
products_id/476 1.84 €
Lens holder http://www.dotlight.de
products_id/48 0.5 €
5 W LED driver ebay UK: teap0t42 £ 4.99
16 mm heatshrink ebay UK:
Miniature toggle switch Maplins FH00A £ 2.29
Waterproof cover Maplins JR79L £1.99
2.1 mm power conector plug Maplins L48AY ? £ 1.29
2.1 mm socket Maplins JK09K £ 1.59
9 V battery case (with innards removed) Maplins L90AN £1.29
RC Battery charger
Maplins QJ37S £ 8.99
7.2 V NiMH 3800 mA RC battery, ebay China: £ 8
Connector for RC battery, ebay
ebay UK: selections-web £ 1.00
Handlebar clamps
Universal Bicycle Mount (22mm~32.8mm) Taiwan: www.dealextreme.com SKU 15342 $ 3.98
1994 Saracen Kilicomp, back in the day when they made top notch bikes. 
it's metallic purple NOT pink. 