My homebrew lights .. finally ...


A long time i set out on here to list out how i was going to build up a set of lights. I never really kept up with the posts and my design changed somewhat since then, so i figured i would complete my task and share the ideas with others.

I took them out on their first full nighttime ride the other day and quite simply, they are fantastic. The fronts are so bright that car drivers flashed me to dip them ... i just pointed them at the ground a bit more. In a couple of cases, some drivers dipped their beam before coming round the corner ! Now thats what i'm talking about :biggrin: :sad:

In another forum, i posted this picture of the throw from my twin 3W Lux red light unit ... remember, this is the REAR light ... :biggrin:


Some people were asking questions about it, so i thought i would share the deets ....

Seriously folks, its blindingly / dazzlingly bright and i think too powerful for using on the roads in all but the absolute worst of weather. I have 2 units of a similar design on the front of the bike which are Seoul P4's and oncoming drivers flash their headlights at me to point them downwards.

I will finish the rear light build though and get it seat / seatpost mounted, just for the sake of completing the build and novelty factor.


As for its components, actually its quite a simple build compared to some excellent detailed work that i have seen posted here in terms of workmanship. Having wasted time and money trying to build something fancy using dimmer controlled boards, i wanted something simple that would switch on and off and thats it. So I spent a LOT of time looking round for the right bits so that the build would be simple and this is result of the internals :


An extruded aluminium case which has an internal dimension of about 20mm x 42mm ... perfect for two 20mm LED's + lenses.
Source: Maplin
Box type: 1455C801

Current Driver:
An all in one driver with integral heatsink. Big bonus was that it has screw in connectors for less hassle of me making an arse of soldering tiny joints. Also 20mm in height ... a perfect fit for inside the box !


See similar products for different versions of the this ( 1A, 700mA, 350mA )

i think they came from But basically, any luxeon start emitter should do the job. Remember, this design will work for front and rear lights

Optics + Holders
Carclo optics and holders ... 20mm in diameter ( oh look, that magic size again ! )
The rears were elliptical lenses.
The fronts were a narrow beam + wider beam in each unit. Great for a good spread of light.

For the rear lenses, to get the lens stripes vertical, i had to file out an extra notch in the holder so the lens would sit in the right direction. ( Its only plastic )


What you dont see above, but is fitted on the final units is a small thin sheet of plastic which covers the front of the lights to protect them from the rain and muck.

LED heatsink / mount
Ah, my master stroke
In BnQ, there is normally a small section where you can buy lengths of steel and aluminium in all shapes and profiles. One of these is an alu C-section shape which is ... you guessed it ... 20mm tall. Cut to the right length and filed down to allow it to fit into the box at the edges and its a perfect sized heatsink/mount combo.

Bar Mount
I used a lumicycle bar mount ( you can buy them as spares online ). If you slot the driver in upside down, then the middle space between the heatsink sides leaves enough space to put a small nut to tighten the lumicycle bolt onto. Simple.


Power source
7.2V RC batteries NiMH. ( these read 8.4V when fully charged )
But basically, if you read the specs on the driver board, then it can handle a max supply voltage of the 2 leds ( 6.5V ) PLUS an additional 4 to 5V on top of that ... so that gives me and input of around about 7 to 11V .... the RC batteries sit perfectly in that range and are easy to source and connect together using tamiya connectors.

Throw it all together and its a perfect little fit with super heatsinking quality and minimal fuss about making it.


so there you go.

What about the price ? I hear you ask. Well, cause i bought the bits of a long long time and wasted money on previous driver boards, i dont have an exact figure. But i reckon that its in the region of about £45 to £50 per light unit, not including the power source.


Don Fisha


New Member


Endurance .... not done a full burn time as yet. But basically my target spec was to acheive a burn time of 2 hours. This was because at the time, my commute was 1hr each way, and i wanted the facility to have lights on the whole time for that.

The front light units use a 1000mA driver unit, and I use two 3300mAh 7.2V RC batterys. So on given a typical 10% efficiency overhead on the driver, thats about 1100mA current drain .... so in theory the batteries should be able to last 3 hours. Even if they dont quite manage 3 hours, then my 2hour target would be easily acheived.

The rear light unit uses a 700mA driver, so with the another RC battery, that burn time should push out a bit more .... again definitely reaching the 2hr target.

In terms of coupling the batteries and lights for the front, I have 2 batteries in parallel which feed a pair of switched ( 1 for each light unit ). So both batteries act as a single unit running both lights. That way, i can then run 1 light off both batteries and further double the burn time if I only use one light.

In terms of being usable on the go: One light unit is easily enough to cycle by in a general manner. At speed, the second light steps in and the pair provide enough light to feel happy at running at full speed down hills. With them pointed at the ground about 3 to 4 metres in front, they dont get drowned out by oncoming headlights. With them pointing more forwards, they'll notably highlight reflective signs about 200yrds away.

The front lights have a narrow spot lens and a medium spread lens in each unit. That way i get a nice wide even spread of light plus a nice sweet bright spot, regardless of whether 1 or 2 lights are on.

If its not crap weather tonight, i'll try and take some pics of them running in complete darkness.
I'm impressed. I'd like one. Can you post links to the LEDs and optics you used? I started looking at optics and just got overwhelmed with the combinations possible. It seemed quite expensive and I didn't want to try things that wouldn't work and then have no further use for them.

Those two bits of info are all we'd need to repeat your success.


Phil, no problem. I understand what you mean about which LED and lens. There is a ton of the out there and easy to get bogged down in it all.

Nowadays, the LED ( or emitters as they are often called ) seem to come in 2 main formats. one where the emitter is just on its own ... so its a small blob with 2 little solder arms on it, or as a star emitter. The star emitter is the same blob, but its already attached to a star shaped heatsink with considerably larger solder tabs. The star emitter is the one to go for - much easier to work with.

Then of course you have the choice of which make of emitter do you go for. Again, there are loads out there. Luxeon are one of the first, but these days, the Seoul P4 and Cree emitters are some of the more commonly available top end choices . The principle factor is lumens. The higher the lumens, the brighter the output. At the time of me buying, the Cree emitters just slightly outperformed the Seoul P4's, but the Seouls were easier to get a hold of, so i went with Seouls P4's. When driven at 1000mA, they crank out 240 lumens each. So my set of 4 cranks out 800+ lumens.

Again, another minefield, and there are all sorts out there. As i see it, there are 3 main categories. Fraen, Carclo and Reflectors.

Fraen and Carclo are similar in that they generally have clear lenses which you hold in place over the emitter with a lens holder.


Fraens are taller and wider ( say about 1" wide and 1" tall ), so they take up much more space. Too much space for my build.

Carclo optics and holders are typically about 20mm in diameter. So the lens and its holder occupy the same space as the star emitter it sits on. This make them great for grouping them together without worrying about spacing the stars apart. from each other.

Reflectors are kind of an all in one unit. More like the reflector of a torch. They needed to come from the states and i wasn't really sure about the dimensions and stuff. Although, from what i had read, certain reflectors offer the best performance of light spread versus loss.

I went with Carclo lenses for my build.


So. Links:

Front Seoul P4's
Rear Lux 3's

Front Spot Beam 6°
Front Spread Beam 15°
( One of each in my front units )
Rear Elliptical Beam

Optic Holders
Carclo Holders

Just take care when mounting the LED's onto the heatsink / holder part. Make sure you put the optic holders on top of the LED's in order to make sure they are in the right place and that you can fit the holders on when the glue has set.

Also there are a couple of other points to this which if you serious about copying the design would help to make things a little easier rather than you having to figure it all out from scratch.
I used a Luxeon 1W emitter wired via a couple of resistors to make an LED bulb, a drop-in replacement for the 2.4W bulb in a front dynamo light (altho I actually power it with a pack of five AA tagged NiMH batteries) a couple of years back. In fact I have pics of it:




It's just a couple of resistors (I didn't have a single one of the right value) soldered into an old bulb cap, with the emitter soldered (carefully) on top. Then I used epoxy to insulate the bits from each other and to fix it all together.

Now you can buy bulbs like this ready-made (but not as cheap) from Nite-Ize and the like - and I believe some of them have constant-current circuits built-in, so a bit more efficient than my crude resistor chain.

But it's not bright enough - I want MORE! Hence my interest. I may well look into replicating what you did in some way, so the clues about the driver, lenses etc are most welcome. I hadn't hit upon either of the .de suppliers you name - they seem well worth knowing about.



New Member
Fisha's lights are seriously bright, I can vouch for that !

I decided to go down what I thought was an easier route.
I used a D cell maglight cut down with a Seoul 3x 3.5W Plug & Light Kit driven by a 1 amp constant current buckpuck. I have a 5 position switch controlling the brightness, I am going to experiment with other lenses as the standard 40 deg lens on the led kit is a bit too wide for the single track road I normally use.
Build was probably around £90 excluding battery and charger.
If I knew how to post pics from my " My Pictures" file I would put some up to let you see the build etc.

LED thingy ...

Buckpuck thingy ....
fisha said:
Also there are a couple of other points to this which if you serious about copying the design would help to make things a little easier rather than you having to figure it all out from scratch.

I am serious. I'm always looking for a better light. What are the other points? PM me if you like.



its nothing secret or anything ... just daft little things like filing down 1 edge of each of the LED bases and also the optic holders so that your wire slots through the gap easier.

i have pictures on CD's somewhere which i'll dig out soon and show you the points i mean.
Fisha, the parts are ordered. Expect plaguey posts/pms asking for details you thought were trivial...

I'm going for a front light initially. I'm planning to add an extra 2000mAh AA NiMH battery to my present pack of five, to up it from 6V and 10 Ah to 7.2V and 12 Ah. The 7.2V should be enough to drive the two LEDs, and the extra capacity won't hurt.

I'm a bit ignorant about these constant current thingies. Could I simply put in a switch between the constant current power supply and one of the LEDs so I can drop to one of them when not so much light is needed? (I like to eke out my batteries by switching to a lower power light when I don't actually need the light to see where I'm going. It helps ease the feeling that my batteries are going to conk out before I reach my destination).


i dont think you would be ableto switch off just 1 led like that.

reason is that you wire them up in series ... one after another.

[+ve driver] <---> [+ve LED1][-ve LED1] <---> [+ve LED2][-ve LED2] <---> [ -ve driver ]

as for the battery, the voltages do add up like that, but the Ah bits bits dont. your overall 5 piece battery is 6V 2000mAH, adding another cell will only increase the voltage, not the Ah part.

so depending on which driver you chose, you basically divide the Ah by the rating of the driver. So a 1Amp driver will last about 2 hours, probably slightly less.

that being said, you could make up a second battery pack, and put that in parallel. That way you would have 2 sources of 7.2V, but also 2 sets of 2000mAh to drive the lights .... so that would give you 4000mAh ... thereby increasing your run time.
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