1300 Lumen Bike Light

Let me start with this: I love biking at night. Everything from the empty streets to the cool air keep me biking into the night. But my quick setup of a LED flashlight pipe-clamped to my stem was not cutting it. I needed more power. I needed a true headlight.

And so was born my second LED lighting project. It totaled about $150 after several trips to the hardware store and a custom water bottle battery pack. 1300 lumens is about the total output of the LED star, the actual output through the lens will be about 10% lower. It is still comparable to both of my car's headlights combined and, even when under-driven, is plenty bright for any biking needs.

Fun Feature - The b2flex board is capable of flashing the LED in a strobe pattern at full strength with an effect similar to a police dazzler. NOT recommended for biking. Blinding muggers and spontaneous rave parties, maybe.

Parts List:
CREE XPG R5 3-up star
3-up Carlco Optics
Arctic Alumina Adhesive (Note: Needs to be the ADHESIVE)
CPU Heatsink I choose this on based on size and a radial design for looks, Personal Choice.
B2Flex LED driver To save money one could use a buckpuck from LEDSupply, I wanted the extra features.
Project Box
2.5mm Jack
2.5mm Plug (I reused some broken headset cords)
Off-mom-on button: Any will work as long as you can easily push it.
Any 3mm or 5mm LED, low power.
Handlebar Mount Be sure to measure your own handlebars to get the right size.
Lexan - At least 3x3 Square, any thickness
1 inch PVC slip plug
Aluminum bar -at least 1" wide, 1/8" thick
Various Hardware
-4 10-36 thread 1 1/2" machine screws with fitting locknuts and washers
-4 small machine screws, max 3/8" long
-A  1 1/2" x 1/4" machine bolt, hex head with matching nut.

Battery Pack:
1x Female Tamiya Connector
1x Male Tamiya Connector
14.4v Battery Pack The size is only dependent on budget.
NiMH Charger
Double-Conductor Cable: I used a old lamp cord
Cheap Water Bottle- Bigger than battery pack
Optional - 3" heatshrink

The battery pack is only NiMH due to the cost of starting a lithium setup from scratch. If you have a 4-cell charger, a lithium pack would be the cheaper (and lighter) route.

Step 1: The Driver enclosure

The driver, the b2flex driver, really is a cool little bit of engineering. Sporting a micro controller, the driver has several sets of configurations for applications like automotive, cycling, camping, and general use. I am in no way affiliated with TaskLED, the driver is just a huge step above the standard buck constant current drivers. But with the added features comes added complexity which I've addressed to varying extents.

First, the mounting holes for the board and holes for wires were drilled out. I then used machine screws and nuts to clamp the board down. Nylon screws and nuts should have been used but it is what I had on hand. No matter what method you use, be careful on how tight you secure the board. The Inductor on the back is brittle and cracked when I tightened down on it.

The interface holes include LED power, the 2.5mm jack, status LED, and battery connection. Sizes will of course vary depending on what cabling and status LED you use. An 1/8" drill will get you pretty far though. To keep wires short, I soldered connecting wires after the board and components were mounted.

To follow my order, install both the 2.5mm jack and the status LEDs without the board installed. Hotglue works for the LED and the jack should be panel mount i.e. clamp right to the enclosure. I had to use a scrap jack and JB weld it in.

Next begin to install the battery connector and the LED leads. For all board soldering, a flux pen is essential. Use a pencil tip iron and carefully begin to add the connections to the board. Connections should be labeled and easy to figure out; consult the b2flex manual if you are confused.

A final bit of hot glue for the battery and LED leads for strain relief finishes the enclosure. Two holes in the corners opposite the closure screws will be used to mount the enclosure to the heatsink.

Comments

[cpotoso]

Nice! But also consider http://www.dealextreme.com/p/900182510 for 1200 lm.

[snowluck2345]

not 1200 lumens, a xml t6 goes upto 900 at 3 amps, I have one, more like 600 lumens. still an awesome light though.

[jeff-o]

I have that light! It rocks. Highly recommended.

[techxpert]

brighter that the sun! great work :)

[espdp2]

Switches bug me. I'm always forgetting to turn them off (though maybe not so much with this fine project). How about an Arduino Teensy or the like and some kind of jiggle switch? Move the bike and headlights, taillights, and EL wire comes on. No movement for one minute cuts it all off. Shouldn't be too complicated, right?

[brainiac27]

Well, the light does have a sleep timer if you are worried. A small Attiny connected to in irregularly-placed tilt switch (maybe horizontal) could keep a mosfet on for a minute longer than the last 'jiggle'. The driver can be set to quiet mode where it turns on when power is applied disabling the strobing startup sequence. A very interesting idea, I hope someone chooses to pursue it.

[tyty100]

@step 3
just like ur pp after ur born

[PearlZenith]

Heck, I'd rather be blinded than surprised by an invisible biker when I'm driving. I bike a lot, too, and should make one of these for myself.

[jmengel]

Have you burned yourself on the heatsink yet? My best guess is that the junction temperature on your LEDs are going to be too high when run at 1500mA. This will translate into reduced LED life, perhaps dramatically so. If this light were left illuminated in still air at 1500mA my guess is the LED life would be shorter than the battery life.

Based on the datasheet for the XPG line, at 1500mA you are dissipating more than 5W per LED. With a junction to solder pad resistance of 6C/W that is a jump of 30C within the LED itself. Being mounted on a star, you've got the interface resistance of the LED package to the star, the star itself, and then the star to your epoxy, the epoxy to the heatsink, and the heatsink to ambient. A good guess for the solder pad through the star to the heatsink would be 3C/W, or 48C at 16W. In still air the heatsink is going to be around 5C/W for another 80C. So you can estimate the the junction temp at 1500mA in still air is going to be around 178C in ambient 20C air which is well above the recommended 150C max. Of course, when riding the heatsink will get convective cooling so that will drop your junction temp somewhat depending on how fast you ride and the ambient temp.

I like the driver, lots of great features. The $32 is a bit steep though. Nice light as long as you keep pedaling! Thanks for sharing your design.

[QuackMasterDan]

Amazing job, this is exactly what an instructable should be -- well-written with good photographs, concise explanation, and a novel and well-implemented idea. It turned out very nicely, great job on the light and guide. Keep up the good work, I can't wait to see what you make next!

[phburns]

Nice build!

I used a module from Lux-RC to build this: http://forums.mtbr.com/lights-diy-do-yourself/microcool-build-sequence-752328.html

[MadScott]

Good build - I'm inspired! One thing to add would be a cylindrical (wide angle) lens to "flatten" the beam into a wide, very flat swath of light that is much less likely to blind cars - I've used this one with some success though there are a lot of people selling similar ones.

http://www.amazon.com/Angle-MagicShine-Gemini-Lupine-Headlight/dp/B004WLCLQY

[roftranspo]

In a later version, could you hook up the battery to recharge from the wheels/gears of the bike while riding so while you riding (especially long rides), you don't have to worry about running out of juice? Just a thought. I do like the use of a heatsink on this build :)

[brainiac27]

It would be a possibility. No dynamo would not be big enough to worry about over-charging so a direct connection would be fine. The hard part would be getting a dynamo that operates above 14.4v to charge the battery. A solar panel for the long sunny rides would work as well.

[roftranspo]

good point on the solar panel. While its in the sun during the day, it can charge the battery for night rides :)

[rox34itl]

braniac27, your build looks excellent! The heatsink you're using looks like one of the stock intel heatsinks that are currently out. Its a creative solution and I like it a lot. I have a spare one, so this might be a perfect use for it.

Also, for the LED light falling off of the heatsink: If the piece that holds the LED light is slipping from the washers you're using to clamp it in place, why not fuse those washers to it? I think you could use JB weld, or some kind of epoxy to do it. You mentioned using hot glue, which I wouldn't use for the purpose I just described. I imagine the heatsink might cause it to melt. o.O I think JB weld is more suited because it can withstand some high temps.

Thanks for the guide!!

[brainiac27]

Much appreciated! And I am still working on the clamping problem. The LED assembly is still held fast by the thermal adhesive (more like an epoxy than a paste), the clamps are only in case of falls or other knocks. I will have to try fusing the washers, v2 of the lens cover may include holes for the bolts built in.

[jortega7]

Good Job with the light, I am a MTB rider, I'm designing a bike light for night roads, my point it's design a portable light (sufficient portable to put the lamp in a MTB helmet), by the current and voltage of your power LEDs I think they will be of 3 W aprox, http://www.agspecinfo.com/pdfs/L/LEDPOT3W.PDF (sorry if the datasheet is in spanish), I have this LED, and works well with 4 Bateries of 1.2 V (in few words the forward voltage of the LED is 3.5 and the average current is 750 mA). I tried a 1W LED (http://twitpic.com/5q5n7q) but I think this is not enough.

What do you think of my idea of portable light?

[brainiac27]

For a headlamp, 3W may be enough assuming it's for closer ranges. But once you get into high power LEDs, constant current drivers are recommended. The following driver could drive smaller 3-up stars and single LEDs fairly well from two AA batteries.

http://www.ledsupply.com/02009-sho.php

Explore the BuckPuck if you want to be more serious about efficiency and life span of the LED.

[rimar2000]

Good work!

[tigerbomb8]

you could use this between the LEDs and the heatsink
http://www.sparkfun.com/products/9771