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DIY Bike Light

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This page describes the construction of a DIY bike light featuring three 3W Luxeon LEDs housed in copper caps with heat sinks. This project had three main goals. 1.) Make a light suitable for use in 24-hour mountain bike racing. 2.) Use readily available material as much as possible. 3.) Offer the details to the community and invite any and all comments.

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#1    Back to top
Pictured at right is some of the basic material required for this project. On the left is a 5W halogen light from a VistaLite system (ca. 2000) from which the handlebar mount will be salvaged. At top are radio controlled helicopter motor heatsinks. The other items follow the goal of using readily available material: 3/4" copper plumbing caps, 1" corner irons, and a 2" long binder clip.
#2    Back to top
This is the key element for the whole DIY bike light. Luxeon LEDs, especially 3W and higher, require supplemental heat dissipation. Without proper conductance of heat away from the diode, it will overheat and fail. At the very least, the LED will operate with reduced efficiency. It just so happens that a Luxeon Star LED fits conveniently inside a 3/4" copper plumbing cap. It's quite possible that the cap alone will provide enough heat dissipation for 1W Luxeons. For 3W and above, an additional aluminum heat sink will only help. An R/C motor heatsink sized for a "280" motor typically fits the 3/4" copper cap very well. The online availability of the green heatsink pictured in this DIY comes and goes, but other 280 motor heatsinks should work. Always check measurements before ordering.
#3    Back to top
Pictured here are some of the specialty electrical items necessary to make a useful light. The two small toggle switches are available at your favorite local electronics supply store. The funny-looking things in the lower left are 2009 Micropuck LED drivers. Add these to the shopping cart when you order the Luxeon LEDs. Finally, the syringes on the right are tubes of Arctic Silver two-part thermal epoxy. This epoxy is the most exotic part of the project.
#4    Back to top
You'll of course need a soldering iron. As you might expect, soldering requires some skill. But don't worry, with just a little practice anyone can learn the process. For some extra help getting started, take a minute to watch the Soldering Tutorial video at Makezine.com. Always wear safety glasses when soldering. Molten metal + Eyeball = Bad. Enlist the help of acid paste flux where appropriate.
#5    Back to top
At last, a chance to unleash your aggression on office supplies! Measure and mark locations to mount the toggles switches. Position the clip in a vise and drill until your heart’s content (or until there is a hole). In this case there will be two switches: one powers up the top LED, the second adds power to the bottom two LEDs so that all three LEDs are on. For different ambient light and riding conditions it is useful to have some control over illuminating your path.
#6    Back to top
In this step, take a moment to fit the 1” corner iron into the clip. Push one toggle switch through the existing hole (you will probably have to enlarge it) and mark the corner iron for drilling a second hole. Did you know the binder clip was invented in 1911 by Washington DC native Louis E. Baltzley (1895-1946)?
#7    Back to top
Get an idea of how to position the Luxeon Star and optics holder inside the copper cap. You’ll want to put holes in the side of the optics holder with the most vertical surface area. In the photo, this is the side lined up with the gap in the heat sink.
#8    Back to top
Check the alignment between the LED housing and the binder clip. Mark the binder clip at the point of contact with the copper cap. This mark will be where you need to drill holes in the clip. Three holes are required per LED housing: two for the screws and one to feed the wires through.
#9    Back to top
Modifying the copper cap is an iterative process. Before modifying the cap, place the Luxeon Star and optics holder inside. Decide where it would be most appropriate to drill holes for the screws. Remove the Luxeon and optics holder and drill the screw holes in the cap. Now reinsert the Luxeon and optics holder and align according to the steps above. Mark the optics holder, remove, drill optics holder. Reinsert, add screws, and decide where it would be most appropriate to drill a third hole for the wires. Remove, drill hole… you get the idea.
#10    Back to top
I know what you’re thinking, “How am I going to fit three holes in this thing?” Trust me, there’s room. In fact, if you look closely at the photo, this particular cap was generous enough to accommodate a half dozen holes! The point is, if you’re not happy with the position of the holes, just rotate and try again. Don’t forget to file down the rough edges before moving on. The insulation on the wires will thank you later.
#11    Back to top
Here the builder is fantasizing that when he drills the next copper cap, the holes will actually be in the same positions as the first. Do the best you can here. To the amateur, small drill bits bend and wiggle all over the place when drilling on the outside of a cylinder. Allow yourself some loose tolerances and you'll have no problem.
#12    Back to top
Put on your safety glasses and fire up your favorite grinder. In order for the top LED housing to fit on the binder clip properly, two fins of the heat sink must be ground off. With aluminum, this task takes little time. The photo at right illustrates that precision grinding is not a requirement.
#13    Back to top
Perfect fit! With two heat sink fins removed, the top LED housing is ready to be mated to the binder clip.
#14    Back to top
Solder lead wires to the LEDs. Wear your safety glasses and make sure you haven’t had too much coffee. You’ll need steady hands for this task. Actually, the Luxeon Stars are designed with generously sized, pre-tinned contact pads making this step easier than you may think. (Note: “generously sized” is a relative term.)
#14a  Back to top
The wiring diagram! Click on the image to enlarge it. The LEDs and drivers in this build feature "buck/boost" wiring. Buck/boost wiring has inverting topology where the output voltage is of the opposite polarity as the unit. This configuration allows for a very wide range of input voltages. According to the ledsupply.com Micropuck applications guide , this driver arrangement works well with voltages between 1 - 7 V. This comes in handy when you might be using your light for various applications requiring different battery packs. One drawback is that this configuration is less efficient than standard "boost" wiring.
#15    Back to top
The Micropucks are wired in parallel in order to properly power 3W Luxeons. In the LED driver world, this particular parallel config is known as "buck/boost." It offers a wide range of input voltage (1 - 7V) and will effectively power the LEDs until the battery is exhausted. The parallel buck/boost config nearly doubles the current over a regular boost config, but sacrifices some efficiency. Click here: to visit an excellent document prepared by LEDdynamics, Inc. illustrating applications of the 2009 Micropuck. The configuration used in this project is described as "Two 2009s in Parallel, Buck/Boost."
#16    Back to top
Connecting the Luxeon Star to the cap is important for two reasons: One, you don’t want the LED to fall out. Two, you want heat generated by the diode to transfer to a heat-dissipating object. Epoxy is used in this project because it eliminates the need to drill more holes in the copper cap and it offers a lot of heat transfer surface area. As you know, most epoxies like a clean surface area in which to bond. Clean the cap by putting a drop of rubbing alcohol on a cotton swab and wipe away any dirt and/or oil.
#17    Back to top
Mix up and apply some thermal epoxy and smoosh the LED against the inside back of the copper cap. If you're using Arctic Silver, or any similar product here, I'm confident you read the instructions. Check your receipt and you'll know why I am confident you read the instructions. This stuff ain't cheap. You don't want to mess up. You think a gallon of gasoline is expensive? If you were to buy a gallon of Arctic Silver, it would set you back $9834.50. (No kidding, $12.99 for about 5ml) Oh, and among other things, it's photo-sensitive. So don't leave it exposed under the florescent lighting of your workbench all afternoon. So, why use Arctic Silver? Because Section 2 of the Arctic Silver instruction manual states, "There is a very good chance that any components you attach with Arctic Silver Thermal Epoxy will stay attached forever."
#18    Back to top
Take a break after adhering the Luxeon Stars to the copper caps. This will allow time for the epoxy to sufficiently harden and for you to relax after the stress of working with the most expensive glue you'll ever handle. Next, slip the wires through the optics holder, insert the #4 screws, and see how everything fits.
#19    Back to top
Mind the gap. If it hasn't occurred to you already. Everything in this light comes together pretty snug. Before going any further check to see that the LED leads are not touching the screw. This could lead to a short or at least an LED that doesn't light. If the wire is not touching the screw but looks close, it might be wise to drop in some non-conducting epoxy between them. But, before you do that, read the next two steps.
#20    Back to top
The O.D. of the optics holder is a bit smaller than the I.D. of the copper cap. If you fit the LED housing to binder clip, the optics holder will be off center. Avoid that issue by inserting a thin washer between the optics holder and the copper cap. Bend the washer to fit.
#21    Back to top
Slide the curved washer in between the optics holder and the copper cap.
#22    Back to top
Proceed with the steps above until you have all three LED housings assembled and ready to bolt to the binder clip. Take your time and think through each step. When ready, pull the leads through the previously drilled holes in the clip leaving some slack on the LED side. Use the #4 screws to attached the housings. Using thread lock compound here is a good idea. Shape the wire in the optics holder in order to accommodate the optics.
#23    Back to top
Connect the Micropuck according to the wiring diagram and stuff it inside the clip. For this project, the two Micropucks were intially epoxied together. However, in order to accomplish this step, the pucks had to be seperated. It's a tight fit and it's only going to get more cramped!
#24    Back to top
Connect the toggle switches according to the wiring diagram. Using acid paste flux really helps to get the solder to bond to the switch leads. Don't forget to slide heat shrink tubing on your wires ahead of time. When finished, cover any exposed wire or switch leads with non-conductive epoxy. Next, locate your magic wand and get ready to mount the switches inside the already-packed binder clip.
#25    Back to top
Behold! The switches magically insert themselves into the clip! Oops, how do I edit out the binder clip handles? Seriously, this is a tricky step. It's nearly impossible without prying open the binder clip. What better way to open the clip than to use is as it was originally designed? With the lights bolted on, the clip will only open partially. But, that is all that is needed to finish this step. Patience is the key. Don't forget to add a drop of thread lock compound to the toggle switch threads.
#26    Back to top
Pièce de résistance! To protect the internals from the elements, the bike light requires some kind of rigid, triangular-shaped piece on the front. What could be more appropriate than a Tazmanian Devil enameled house key? After a few minutes work with the grinding wheel, the head of the key was shaped to fit the opening in the clip. Also picture here is some hardware required to attach the handlebar mount. The neoprene washer may be used to help waterproof the opening in the front of the clip. For some positionability of the light, use salvaged bicycle brake pad washers. They are curved to allow a bit of a swivel motion before tightening.
#27    Back to top
In this photo you can see how the salvaged Vistalite handlebar mount is attached to the corner iron.
#28    Back to top
The bike light is now fully assembled. Well, except for batteries and a battery connector. In future updates I'll show some examples of DIY battery cases, but for now, I'll leave that up to you. In this photo the lenses are snapped into place. On the top is a regular 15 degree lens. The bottom two LEDs feature 10 degree collimating lenses.
#29    Back to top
5-Watt halogen light (shown in step #1) powered by 6 Volts. Photo taken at a distance of 20 feet with 1.3 second shutter delay.
#30    Back to top
Single 3-Watt Luxeon III with 15 degree lens powered by 6 Volts. Photo taken at a distance of 20 feet with 1.3 second shutter delay. Mouseover image to view the light with all three 3-Watt Luxeon IIIs illuminated.
Recommendations
1.) A Luxeon III Star can handle 1400 mA. The High-Output MicroPucks used in this project combine for 700 mA. At 700 mA, a single Luxeon III Star has a luminous flux of 65 lm. Use Super High-Output MicroPucks for a combined 1000 mA output. At 1000 mA, a single Luxeon III Star has a luminous flux of 80 lm. Brighter light, same price! 2.) Reposition the handlebar mount to some point beneath the light. This will help balance the weight and should allow you to swivel the light without using brake pad washers as described above. 3.) May 1, 2007. Per feedback from the LED Supply Sales Team, the wiring diagram has been revised. See step #14a. 4.) Oct. 20, 2007. Visit San Francisco rider and Yahoo! engineer Jim G.'s amazing collection of links to DIY bike lights here: yojimg.net 5.) Dec. 19, 2007. Binder clip is actually 2" in length, not 1-1/2". See Step #5 above. Thanks Will. 6.) Jan. 23, 2008. By far the most time consuming part of this project is fabbing a custom light housing and configuring the handlebar mount. A very helpful visitor to this site brought to my attention an Australian company that sells a DIY housing kit for a bike light. The price of the kit is more than the entire project described on this page, but it may be worth it considering your labor time. Plus, the kit appears to have the advantage of being much more weatherproof than the binder clip! Check it out: www.cutter.com.au Thanks Ron.
Props
Recognized as one of "five of the finest looking homemade bike lights on the web today" by Bikehacks.com, January 31, 2008.
Featured Instructable at Instructables.com, November 7, 2008.
Runner-up in the Instructables.com "Light up your Ride" contest, December 2008.

Shopping List
			(Prices in USD)
Item Name	Link to Item	Qty	$ Each	Subtotal
Luxeon III Star, White, Lambertian	ledsupply.com	3	6.99	20.97
Luxeon III Star Optic Holder, White	ledsupply.com	3	0.25	0.75
Optics, Collimating 10 deg	ledsupply.com	2	2.49	4.98
Optics, Narrow beam 15 deg	ledsupply.com	1	1.50	1.50
High-Output Micropuck Drive Module	ledsupply.com	2	9.99	19.98
Arctic Silver Premium Thermal Epoxy	ledsupply.com	1	12.99	12.99
Micromini toggle switch	radioshack.com	2	3.99	7.98
Aluminum Heat Sink for 280 Motor	Google Products	3	1.75	5.25
3/4" Copper Plumbing Cap	Local Hardware Store	3	0.60	1.80
1" Corner Irons (package of four)	Local Hardware Store	1	1.18	1.18
2" Long Binder Clip	Local Office Supply Store	1	0.25	0.25
Tazmanian Devil House Key	Local Hardware Store	1	4.99	4.99
Miscellaneous Hardware	Local Hardware Store	-	-	3.00
Miscellaneous Electrical	Local Hardware Store	-	-	3.00
Salvaged Handlebar Mount	-	-	-	-
Grand Total	-	-	-	88.62

Comments

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Date: 3/19/2007 Comment By: samsmeg So when do you reckon the battery case idea will come about? Your idea of using these leds is so much better my idea of using 12V 20w Halogen Bulbs on my own homemade light! I must get the parts for this light design and use it on my road bike, awesome!

Date: 3/21/2007 Comment By: RDN Send in a photo of your designs (both present and future)! The battery case designs will be posted soon. They are constructed using basically the same principles as this light – suitable for racing and from readily available materials.

Date: 3/19/2007 Comment By: jccoons Love the idea - I just purchased the items on your shopping list. I will let you know how it goes when they arrive. Very interested in your DIY battery packs as well. Thanks for the detailed post.

Date: 3/21/2007 Comment By: RDN Thanks! Please post back to let us know how your project goes. Also, send any photos to service@racedaynutrition.com and I’ll get them posted. One bit of advice I have is to redesign the way the handlebar mount is configured. With the design described above, the weight of the light is out in front of the bar which may cause it to rotate down. Try a design where the weight of the light is centered above the centerline of the handlebar for better results.

Date: 3/19/2007 Comment By: mpap89 what kind of power source are you using?

Date: 3/21/2007 Comment By: RDN The power source used in all of the photos above is a 6V DC 285 mA transformer. I typically use four C cells at 3000 mAh to power a 5W halogen. I may use the same four C cells for the LEDs – I’ll just get longer run times. I will post battery run times for this light when they become available.

Date: 3/20/2007 Comment By: vvvlado But why 'High-Output Micropuck Drive Module'? It delivers only 350-400mA. It is designed for 1 Watt LUXEON leds. 3.5-4.0V x 350-400mA = 1.2 - 1.6W. Isn't it better to use BuckPuck drive for 1000mA? It also has dimming capabilities.The difference is that MicroPuck requires lower voltage (3V) and the BuckPuck requires at least 5V and at least 1V more than the LED operating voltage - 3LEDs = about 11.0-11.5V. Higher voltage - lower current drained from the batteries. I have a bike light which uses one 3W LUXEON Star LED, a BuckPuck drive, 4x1.25V Ni-MH AA batteries and a 5kOhm potentiometer utilizing the BuckPuck dimming capabilities. The LED is mounted to a heat sink using two screw bolts and the same heat conductive material used for processors. I would put more LEDs or more powerful ones if I had an easy power supply solution. There are some 12-14V packs but I am not sure if they can be easily mounted.

Date: 3/21/2007 Comment By: RDN The BuckPuck is certainly a viable option. As you noted, the BuckPuck requires a higher minimum voltage. The MicroPucks, as configured in this setup, require 1-7 volts and deliver 700 mA. Therefore, if your primary battery pack happens to die, you may still ride out of the woods safely on that single AA cell you tossed in your seat pack as a spare. Another factor for choosing the MicroPucks was size (0.83”x0.83”x0.43” for the BuckPuck vs. 0.45”x0.3”x0.26” for the MicroPuck). Readers take note, there is now a Super Hi Output MicroPuck driver available that delivers 500 mA. Wire it as described above and you’ll get 1000 mA.

Date: 3/20/2007 Comment By: phil Hi there...We find your DIY MTB light very interesting. As we live in South Africa parts for this project might be dificult to obtain. Would there be any chance of getting a kit put together by yourselves and sent to a friend of ours in the States? Thank you very much and I look forward to any replies.

Date: 3/21/2007 Comment By: RDN I don’t think that would be a problem. Send a note to service@racedaynutrition.com to arrange. Thanks for your interest!

Date: 4/4/2007 Comment By: adammarksteiner Great design, I should be getting parts to build one today. I think I'm going to try a bit different design, putting the lights on the fork and with 2 led's on one side and one on the other. I also want to make them so I can use them as headlamps for those long Minnesota nights of x-country skiing. One note, the back surfaces of the stars need to be electrically insolated from eachother, you don't seem to have a problem with it, perhaps because arctic silver is not electrically conductive, but at least in if the right circumstances you could have some problems. I guess the best thing to do would be to isolate each of the 3 housings, so as not to mess up the heat transfer.

Date: 4/20/2007 Comment By: greggiles Your wiring diagram shows connecting the LED from O to B, whereas the AppNote shows O to R . . . is this on purpose? Also my quick reading of the driver is that it strives to maintain 700mA, does running the three LEDs in paralell cause the brightnes of the main light to drop? Overall great article, I ordered some parts last night!

Date: 4/24/2007 Comment By: RDN I'm pretty sure that as long as you have at least 700mA coming from your batteries, the lights will not dim. I will submit the wiring question to ledsupply.com and see what the good folks over there have to say. In the mean time, if any Double-E's would like to respond to greggiles question above, please feel free. Update: 05/01/2007 - According to ledsupply.com, there will be some dimming of the LEDs through the use of this driver. In addition, the wiring diagram has been revised. Thanks for questions, greggiles.

Date: 4/25/2007 Comment By: iroberts I'm about to order the parts to build my own lights. Any other comments or updates? I will be shiping parts to New Zealand and using 4 x Ni-Mi AA. as battery pack. Its a long and expensive trip to miss some details. Thanks Ian

Date: 5/2/2007 Comment By: RDN iroberts: The parts list is good. Order with confidence. Follow the recommendation above and design your light so that the weight is centered above the handlebar. Four NiMh AA batteries should be ideal. Cheers.

Date: 6/15/2007 Comment By: darren Hi RDN,very detailed instructions. what was the weight of the end product. I am looking to replicate your light but I would like to use 5w 120Lm luxeon star LED's. Do you think this feasable? I'm not electronics savvy so I need to ask your opinion of what may be required. Any help woud be appreciated.

Date: 7/09/2007 Comment By: RDN Darren, I have not weighed the light yet. As for the 5W LEDs - I say go for it. I think the heat sinks in this project are sufficient for the more powerful LEDs. Just take your time and make sure you use the correct driver. Let me know how it turns out. Thanks!

Date: 7/10/2007 Comment By: cadenaja Hello, I'm about to put this together with the High-Output MicroPuck instead of the Super High-Output Micro Puck, how long would four (4) NiMh AA batteris last?

Date: 8/26/2007 Comment By: RDN I haven't timed 4 AA batteries yet, but it should give you over two hours. Let me know how it works out for you. Good luck.

Date: 8/28/2007 Comment By: normafleming L.E.D.'s are the wave of the future. Halagens H.I.D. & Xenon are all cool, but for power consumption-You can't beat L.E.D.!! These Stars are powerful! I am NOT electric-Savvy & simplified schematics would help. I am mostly interested in how to wire a single Luxeon Star to a helmet? Can you draw me up some simple wiring for a toggle switch & a power source? I considered drilling the "T"-handlebar on my scooter & mounting them directly to the bar itself (at least one). The toggles will also be mounted directly to the "T" too. That way, the wiring is always protected!