Homemade *bright* LED light setup

[Mussels]

Have you considered reducing the number of LEDs and using the new high performance ones?

[Haku]

High performance ones such as the Luxeon Stars & Cree XLamps require collinators & heatsinks, increasing the overall physical size of the light, my aim is to make it as small and powerful as possible and unnoticable as possible when it's not switched on - hopefully such a tightly packed array of 15x20 3mm LEDs will in the daytime from a distance just look like a slightly large reflector.

[torrent99]

High performance ones such as the Luxeon Stars & Cree XLamps require collinators & heatsinks, increasing the overall physical size of the light, my aim is to make it as small and powerful as possible and unnoticable as possible when it's not switched on - hopefully such a tightly packed array of 15x20 3mm LEDs will in the daytime from a distance just look like a slightly large reflector.

Just ordered 100 5mm 5000mcd red LEDs myself...although I won't be going to the same lengths to line them all up. I'm after visibility from a range of angles, rather than as a headlight, so a bit of higgledy piggledy won't do any harm.

[Haku]

The best way to get visability from a range of angles is to file the heads completely off (angle grinders do the job in seconds), turning a normal domed LED into a flat-top increases the viewing angle to almost 180degrees, so no matter what angle you're looking from it'll always be a very bright dot.

I may well do that to the LEDs on the sides of my intended new light, facing the edge ones 90degrees to the others and have their heads filed off.

[Haku]

Just placed an order for a PICAXE 18X starter kit, a programmable microcontroller with 5 inputs & 8 outputs (one of which has pulse width modulation capabilities so a light can be dimmed to almost any level), programmable with something called pbasic so it shouldn't be too difficult to program a lighting setup

I will be using 4 (maybe 5) inputs and all 8 outputs, with the outputs wired into FETs that can handle the high current of mutiples of 60 LEDs (front light will be wired as 5 sections of 60 LEDs), and this should be a nice intro to programming my own chips for any future projects.

[torrent99]

I am in the process of designing my 3rd major incarnation of my bright LED light setup, I found as I thought that I'd be using the entire 60 LEDs almost all the time I'm on the road at night which does make me more visable but doesn't give me the ability to hi-beam, and I've been wanting more light for dark roads/paths. Night cycling with a very bright light setup is fun.

So after seeing that Dimension Engineering now sell a very small DC-DC step-down regulator capable of taking up to 35v and delivering 25watts with over 90% efficiency, I realised I can go ahead and make my 'monster' headlight; a very tightly packed array, 20x15 = 300 3mm LEDs in an area of 8cm x 6cm, 5 times the brightness of my current light in just 2x the area.

In order to pack the LEDs so tightly I've got to try and persuade a friend to do a favour for me; design & have made a circuitboard to hold all the LEDs+resistors as there's no way I'd be able to accurately drill out a grid of 300 3mm holes by hand in some plastic with a 1mm gap between them, even with a milling machine like I did with the original 60 LED light.

On the subject of DC-DC converters, the folks on EndlessSphere have been having quite a bit of luck using mains switching (i.e.transformerless) power supplies e.g. old phone chargers. It seems many of them aren't fussy about the voltage they receive...

My new low tech (i.e. resistor driven) 60 (5mm 5000MCD) LED back light made from old blister packs from AA batteries, cardboard "circuit board" and gaffer tape is now installed!

The 18 (10mm 15000MCD) LED front light has been working well for a few weeks. Much better than most of the addon lights you can buy and no-one will want to nick them! [Constructed from an old dynamo front light+ grease proof paper diffuser]

[Haku]

torrent99, post a pic! it's always interesting seeing how people solve the problem of seeing at night on bikes


A week ago I ordered a PICAXE 18X starter kit for building a bike light 'simulator' and getting back into the deep thinking of programming loops/states/inputs/outputs again. Last the weekend I finished this little box:



using all 5 inputs and all 8 outputs. (superbright LEDs are so difficult to photograph!)

Row of 5 LEDs represents the 300 (5 x 60) LEDs of the front light, the single red & white LEDs are going to be on the caps of the axles of the bike and the two large LEDs next to each other represent the 16 bright red LEDs of the rear light.

As for programming it, I've made a program that works - off/low/med/high/highbeam capabilities of the front light plus rear & side lights on, but having a real headache trying to program it so buttons have dual/triple roles depending on wether they're pressed on their own, held down for a certain amount of time or pressed down at the same time as another button.
I've written the main code twice but each iteration isn't capable of incorporating dual button presses & buttons held down for a certain amount of time. Just have to keep trying to think of new code it I guess.

[Haku]

Rewrote the program 3 times, 3rd time nailed it, I'll have to take a video of it or something because it's quite neat, pressing the highbeam button makes all the front light LEDs go on only whilst it's being pressed down, but press a 2nd button whilst the highbeam button is pressed and that locks the highbeam to ON, pressing the highbeam button again turns it off.

Today I got the circuitboard designed & sent off to be made, friend of mine has a circuitboard designing package that costs as much as a nice new car (!), this is a rough drawing I did of the final board:

A single 83mm wide board containing 60 3mm LEDs each spaced 4mm apart, ordered 15 of the boards so I got spares for other projects & if anything goes wrong, cost for the 15 boards without solder resist & silkscreening (white writing on the board denoting where the components go etc.) came to a mere £75... £5 per board! still, should be worth it in the end though

Now I'm off to order 1000 3mm white LEDs (only £29 from Hong Kong) & the required resistors, not sure wether I want 100ohm or 120ohm, using 100ohm will give slightly brighter LEDs but may reduce their lifespan.

edit: Just ordered; 300 120ohm resistors, 5 momentary pushbutton switches, 1000 3mm white LEDs, 500 3mm red LEDs (at 1/6 the price of UK bought ones, hell why not get 500 instead of 50! plenty of spares for future projects ), total for that little lot was around £55

[torrent99]

Rewrote the program 3 times, 3rd time nailed it, I'll have to take a video of it or something because it's quite neat, pressing the highbeam button makes all the front light LEDs go on only whilst it's being pressed down, but press a 2nd button whilst the highbeam button is pressed and that locks the highbeam to ON, pressing the highbeam button again turns it off.

Today I got the circuitboard designed & sent off to be made, friend of mine has a circuitboard designing package that costs as much as a nice new car (!), this is a rough drawing I did of the final board:

A single 83mm wide board containing 60 3mm LEDs each spaced 4mm apart, ordered 15 of the boards so I got spares for other projects & if anything goes wrong, cost for the 15 boards without solder resist & silkscreening (white writing on the board denoting where the components go etc.) came to a mere £75... £5 per board! still, should be worth it in the end though

Now I'm off to order 1000 3mm white LEDs (only £29 from Hong Kong) & the required resistors, not sure wether I want 100ohm or 120ohm, using 100ohm will give slightly brighter LEDs but may reduce their lifespan.

edit: Just ordered; 300 120ohm resistors, 5 momentary pushbutton switches, 1000 3mm white LEDs, 500 3mm red LEDs (at 1/6 the price of UK bought ones, hell why not get 500 instead of 50! plenty of spares for future projects ), total for that little lot was around £55

Looking good!

Re: the resistors, you might want to do some experimentation on this as the specs of the HK LEDS I got seem to vary quite a bit I found that my LED chain was pulling 40ma (LED rated at 30ma) even though I'd done all the calcs! I kept getting LEDS blow after a time. I've added a couple more LEDS to each chain now to reduce the current to 30ma, so hopefully they'll last a bit longer.

Also it's probably worth running the lights off the bike on a soak test for a few days, I've had several early deaths (not due to overcurrent). It'd be best to get your swap outs done before you spend the time mounting them.

[Haku]

Yeah soak test is a good idea, I'll be running the LEDs from a stable 12v source, 25watt DC-DC converter which is adjustable so if I find the LEDs are burning out I can simply lower the voltage. I stuck to 120ohm resistors which is for 3 3.2v LEDs in a row each drawing 20mA, whereas the LEDs I bought are rated for 3.4-3.6v, undervolting them will extend life & reduce brightness but heck there's going to be 300 of them so it can't be all that dim!

BTW, I just found the ultimate LED bike light: 100 watt LED (but it costs £240+)