Mountain Biking - DIY lighting project begins

I went to the LBS to see if they had any decent lighting systems that cost less than my bike and they were all unsuitable for night trail riding. I decided to put together my own LED lighting system with six 1W LEDs and a bunch of 5AH C-cell NiMH batteries with tabs.

Here are the LEDs:
http://www.theledlight.com/starswith_optics.html

and here are the batteries:
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=217

I plan to assemble a pack of shrink-wrapped batteries inside the frame/seat post. That way, they won't fall off or interfere with other things and I'll still have my bottle holder open. I don't know how many will fit, but I'll include as many as will fit. Based on that, I'll decide how to arrange the LEDs in the circuit. If I can fit 10 batteries in the frame, I'll have 60WH to work with which will mean about 10 hours of run-time with all 6 LEDs on. I'll build a custom car charger so the bike can charge up as I rest or as I'm transporting it.

Does anyone have experience with high-wattage LEDs? The only one I've seen is the 3 watt luxeon my dad has in his flashlight. It's pretty decent, but I'd like more for trail riding at night. I guess if 6w is not enough, I could always order six more for a 12w LED array.

sounds interesting. unfortunately I don't have a lot of experience with LED's so I'm not sure what to say/recommend. Post up pics as you go though! I'm really curious as to how this will turn out.

That's right. I'm sure a lot of guys will be waiting for the pics.

Wow. it's what Ihave been waitting for. Please post lot's of picture with.
By the way, I want to someone makes HID DIY. I did my other car's HID headlight as DIY but have no idea about bike light.:o

I still like the 10watt halogens over the 10watt equivilent LEDs...

I've been meaning to do this for a while - here are some links I've found if they help:

http://www.instructables.com/id/E3BGQT6Y7PEP286N6P/
http://www.bike-recumbent.com/headlight.shtml
http://www.members.optusnet.com.au/richardbtt/richards_bits/DIY_Lights.htm

Post pics!!

Wow. it's what Ihave been waitting for. Please post lot's of picture with.
By the way, I want to someone makes HID DIY. I did my other car's HID headlight as DIY but have no idea about bike light.:o

All the bike HID bulbs come from the same company, they know you will build a bike light if you buy a bulb so they price things so that it is cheaper to buy a finiished light from a bicycle light maker. They protect the best customers, they are smart. There is no reason to make your own it would triple the cost of a finished light you can get now. Forget the idea for now.

They flat out say it on the web site.

"Solarc" or solarc bulbs is the site. Made by Welych-Allyn.

I know I could have gone the halogen route, but I don't find it nearly as impressive as a high power LED array. Also, the runtime and dependability wouldn't be nearly as good. A 3w LED is quite impressive to see and the bike lights that come equipped with them are expensive for no good reason. I'm anxious to see how bright 6w (or even 12w) worth of LED light can get.

Does anyone remember those hand guard type things that are popular on dirt bikes? Do they make them for mountain bikes? If so, I think if I had to use 12 LEDs, they would be a good option for mounting them since my shift/brake cables interfere with handlebar mounted lights. I figure six on each side should be plenty to light up the night and still give a good five hours of runtime.

I'll also have to come up with a current regulator circuit to drive the leds at about 32mA from the battery pack. I'm pretty sure I can throw together a MOSFET based circuit that will do the job. For testing purposes, I'll assemble the LEDs and drive them with a 12v source and limiting resistor. This is too wasteful to use on a bike, but I'll have a good idea of what the LEDs are capable of and will post pics.

Still awaiting parts...

I am in the lighting industry. In laymans terms keep in mind the LED's while having crazy intense pearcing light, the carry on it is minimal. Try it with your LED's vs incandescent flashlights. The LED will provide you with a high lumen level but the footprint ( or area occupied ) will be very small. We have the same problem with using LED's to light roadways. Its about halfway there, but still needs alot of RnD. Some of you may have noticed it in your towns and roadways, but its still a beta test in most cases...

just my $.02

I've seen ****ty 3watt Luxeons and great 1watt Luxeons and they're about the same. I don't know what makes the lame 3watters so dim. Resistance value? dunno. But I've also seen impressive 3watters from like SureFire flashlights.. dang.. they're pretty impressive.

If you can get them to work efficiently.. try moving on to 5watt Luxeons and publish some results!

I know I could have gone the halogen route, but I don't find it nearly as impressive as a high power LED array. Also, the runtime and dependability wouldn't be nearly as good. A 3w LED is quite impressive to see and the bike lights that come equipped with them are expensive for no good reason. I'm anxious to see how bright 6w (or even 12w) worth of LED light can get.


I would think that 1 3watt led would be brighter than 3 1 watt LEDs .. just beacsue the 1 source would be easier to focus. Am I wrong here?

I have a 3 watt led flashlight and a 10 watt halogen bike light.. I use the flashlight on the helmet occasionally the halogen is definately brighter. My flashlight is of the 10 dollars on ebay direct from hong kong variety though.

I recently was at an LBS for a light demo. It had a bunch of Halogen, LED and HID light systems on display. I've dealt with the owner a few times so when it was essentially over, we went out back to a park and tried them. I was most impressed with the Cateye Double Shot, the LED, I was showed. I ended up buying it and it was stellar on a recent night ride.

The trail I usually go to is fairly tight but when there was 100 yards of straight, I could illuminate the entire straight with the lighting. It also had a good halo of decreasing light of probably about 15' or so (probably more) when used directly in front of me and helmet mounted.

I guess the point of this post is to say good luck and if the LED light is designed well enough, it should be more than enough light for trail riding. Also, as the name implies, it only had 2 LEDs. I do not know what wattage or any specs on them, but I'd imagine it shouldn't be too hard to find.

FWIW- I ended up spending about $200, which is about the HID price, so that wasn't a deciding factor, just the light emitted.

FYI, there is a gigantic thread on this in the Commuting sub-forum. It's called "Total Geekiness" and is stickied up top. There are literally hundreds of posts on DIY lights. Personally, I'm using the Batteryspace/Trailtech combo. 13W HID with 4.5 hr runtime. The battery is a Li-ion and weighs just over half a pound. The light itself is fairly hefty, but I got used to it after two rides. $239 - best money I ever spent on a light, bar none.

I would think that 1 3watt led would be brighter than 3 1 watt LEDs .. just beacsue the 1 source would be easier to focus. Am I wrong here?

These LEDs are integrated with the optics, so they project a fairly narrow beam (10-15 degrees) right out of the box.

My goodies have arrived! I mounted the 6 LEDs to a PCB, studied the datasheets for a while and fired them up. The nominal current for the LEDs is 350mA, but to be on the safe side I ran them at 240mA.

All I can say is HOLY #@%#! These things are BRIGHT. From 20 feet away, it hurts to look into them. I really doubt I will need any more LEDs. I tested them indoors in my pitch black basement and they lit most of it up.

Right now I'm working on the on-board current regulator. Because of the discharge curve of the NiMH batteries, a simple dropping resistor will not do. With a resistor, I'd either have to:

1. Charge them up to 1.2v per cell to get a relatively flat discharge curve, forfeitting 20% of the battery life or..
2. Charge them to full capacity but deal with the 50% reduction in brightness beyond an hour of runtime with a larger resistor value.

Both are unacceptable, so now I'm testing my MOSFET regulator circuit which only needs 0.5v of headroom to operate. The regulator will keep the LEDs lit at maximum safe current as long as the battery pack provides at least 10.8 volts. After that the regulator effectively cuts itself out of the circuit, and brightness will drop off very slowly as pack voltage drops.

Pics are coming!

Preparing the PCB for the LEDs



Test fitting one of them

The LED light shining on a wall inside my basement at 20 feet away. Keep in mind this camera sucks in low light and the flash is disabled. All the lights in the room are off. The rectangular yellowish spot at the bottom is a cheap incandescent bike light with a fresh change of batteries shining on a toolbox at the end of the room. If you can't see it, try turning up the brighness on your monitor. The cheapo light can be seen in the lower right hand corner and compared to the big white spot of the LED light, it sucks. This picture illustrates how bad my camera is in low light. The spot is much more impressive in person.

The completed board with the built-in regulator.

This one was taken with the lights in the room on. The camera is still overwhelmed at 18' away.

A shot of the rear of the board.

The completed board with the built-in regulator.

Another nice thing is that it works as a "be seen" light, although the angle is fairly narrow. It will work in be seen mode long after the batteries are "dead" whereas incandescents and HIDs even more so go from usable brightness to completely out within a fairly short period of time. Hooked up through a 39K resistor, all six LEDs light up to the point where you can see them at a distance. Connected this way, the batteries should last over a year (not counting self-discharge).

I've seen ****ty 3watt Luxeons and great 1watt Luxeons and they're about the same. I don't know what makes the lame 3watters so dim. Resistance value? dunno. But I've also seen impressive 3watters from like SureFire flashlights.. dang.. they're pretty impressive.

If you can get them to work efficiently.. try moving on to 5watt Luxeons and publish some results!

Heat would be my first thought. A lot of the LED packages at this wattage need to be surface mounted to a copper plane of n area in order to hit their Tj numbers. The hotter the PN junction gets the less light you'll emit as it takes more voltage for the electrons to cross the potential well of the depletion region. More voltage = a higher Vf forward voltage drop and thus a lower voltage across the junction itself... which directly translates to lower current and fewer photons being created as the electrons shed their energy.

In other words, HEATSINK the crap out of the Luxeons, but watch the time above liquidous on the diodes as the junctions can also be damaged by excessive heat.

Anything else?

My goodies have arrived! I mounted the 6 LEDs to a PCB, studied the datasheets for a while and fired them up. The nominal current for the LEDs is 350mA, but to be on the safe side I ran them at 240mA.

All I can say is HOLY #@%#! These things are BRIGHT. From 20 feet away, it hurts to look into them. I really doubt I will need any more LEDs. I tested them indoors in my pitch black basement and they lit most of it up.

Right now I'm working on the on-board current regulator. Because of the discharge curve of the NiMH batteries, a simple dropping resistor will not do. With a resistor, I'd either have to:

1. Charge them up to 1.2v per cell to get a relatively flat discharge curve, forfeitting 20% of the battery life or..
2. Charge them to full capacity but deal with the 50% reduction in brightness beyond an hour of runtime with a larger resistor value.

Both are unacceptable, so now I'm testing my MOSFET regulator circuit which only needs 0.5v of headroom to operate. The regulator will keep the LEDs lit at maximum safe current as long as the battery pack provides at least 10.8 volts. After that the regulator effectively cuts itself out of the circuit, and brightness will drop off very slowly as pack voltage drops.

Pics are coming!

Look into Supercaps to stiffen the circuit with. Cooper-Bussman makes good ones that are pretty small and pack 50 Farads at low voltages [2.5V?]. If you're regulating it anyway you can use the caps to store additional power at a pretty low weight cost.

Heat would be my first thought. A lot of the LED packages at this wattage need to be surface mounted to a copper plane of n area in order to hit their Tj numbers. The hotter the PN junction gets the less light you'll emit as it takes more voltage for the electrons to cross the potential well of the depletion region. More voltage = a higher Vf forward voltage drop and thus a lower voltage across the junction itself... which directly translates to lower current and fewer photons being created as the electrons shed their energy.

In other words, HEATSINK the crap out of the Luxeons, but watch the time above liquidous on the diodes as the junctions can also be damaged by excessive heat.

Anything else?

Take it all back, since the datasheet shows the diodes pre-mounted to alumina. Sorry for the geek response.

Take it all back, since the datasheet shows the diodes pre-mounted to alumina. Sorry for the geek response.

Is that enough of a sink though? Their backs are to a PCB and they're only somewhat warm, I'm guessing around 110F. Also, the circuit is current regulated, so Vf shouldn't be an issue. Each LED is designed to run at 350mA so since I have two strings, it should be 700mA. The circuit supplies 620mA at room temperature, leaving a decent margin of safety.



Look into Supercaps to stiffen the circuit with. Cooper-Bussman makes good ones that are pretty small and pack 50 Farads at low voltages [2.5V?]. If you're regulating it anyway you can use the caps to store additional power at a pretty low weight cost.

What will caps accomplish? This is a fully DC circuit, the load and the supply are fairly constant.

I know it's a little late to add this, but it might be helpful. www.bikelight.blogspot.com

Every one keeps telling me that Luxion LED's are not that good- I have the Exposure Enduro Turbo as the in the link and this is twin 5 watt luxions. Just tried to get pics to prove it but I am not used to the camera and can't get it to run properly so sorry just believe me.
Last year I used a twin 10 watt halogen. Not bad but still only just on the edge of usable at speed. Spot light ran out of real power at about 40 yards and was a distinct spot light and the flood did not fill the gap from the front wheel to the spot. My halogen spot on the helmet was more usefull as this was a tight beam for 50 yards and this is only a 2w bulb so must be down to the quality of the lens.

The Exposure throws light from the front wheel to 60 yards in front and it is full up to that point and then it stops.The beam is also wider than last years lamp and no unlit area at all in the range of the lamp.
No external battery- so no leads to fall off or get pulled out and I can get 8 hrs on low light that gives as good a light as the twin halogen. On the turbo I only get 2 1/2 hours but you do not use the turbo that often. Disadvantage- It is still expensive.

High power luxions are not here yet but I rate this twin 5w as good as the mid price HID's that I tested and better than the cheap ones. No way will it compare to the top of the range though but that will come. Probably at a price that puts them out of the market for most of us but they will come.



http://www.use1.com/exposure/products/exp_enduro/index.php

High power luxions are not here yet but I rate this twin 5w as good as the mid price HID's that I tested and better than the cheap ones. No way will it compare to the top of the range though but that will come. Probably at a price that puts them out of the market for most of us but they will come.


You can't get as much light out of 10 watts of LED's as you can out of 10 Watts of HID. It's not possible.
You get more lumens per watt with the HID bulb. I don't know of any HID's on the market that are less than 10watts. There might be one somewhere.

LED's (~20-30 lumens/watt) HID's (~50 lumens/watt)

My HID is 59.375 lumens per watt.

I enclosed the board in a VHS-C cassette case and mounted it to my handlebars. I tried putting the batteries inside the seat post but there were too many complications so I just strapped them to the outside of the frame. I went for a ride from 2:30AM to 4:00AM and it worked quite well. The lights were bright enough that I could see a dead cat from about 25 yards away, plenty of time to avoid it. I may build a second cluster sometime in the future, but for now, this works pretty well. The batteries held up well in freezing weather too.