This instructable is created and provided by the Edmonton Bicycle Commuters' Society (EBC) ( , , ), a non-profit organization that supports all cyclists in Edmonton by providing advocacy, education, free services at events, affordable used and new parts, and bicycle recycling.

EBC also operates BikeWorks, a fully-equipped, volunteer-run community bike workshop, where volunteer mechanics teach & help members of the public to learn how to fix their bicycles. EBC also sells used bikes.


This is the introductory video to building a high-power three LED bicycle light. The design here has 3 modes: High, Medium, and Strobe (blinking), and runs on a voltage between 5-10V. The price of the light, including batteries, charger, and worldwide shipping, is about $50 US. Including batteries, it weighs about 200 grams, and should last about 1.5 hours on high mode (and significantly longer on medium or strobe modes).

This light is something that you can build with minimal investment in components and small hand tools. You don't need to know electronics: there are just 18 solder points, 6 drill holes, a bunch of hot glue, and a few screws. It doesn't require a microcontroller. You don't need to know what an Arduino is. It doesn't require you to fabricate metal, use PVC tubing, laser cut anything, or weld. With a bit of experience (e.g. if, for whatever reason, you make a half-dozen), you can put one of these lights together in less than an hour.

The Edmonton Bicycle Commuters' Society occasionally runs in-person courses on designing and building your own custom bike lights: this design or one customized to suit your needs.

This light is the same brightness, about 600 lumens, as the "Three P4" design here: , but the design in this video is cheaper and easier to build and use, and has a cleaner design.

This light works in thunderstorms, blizzards, and has been used in temperatures below -30C.

That power source can be two lithium-ion rechargeable batteries, or four to six alkaline 1.5V cells in series, or five to seven rechargeable NiMH or NiCad 1.2V cells in series (any of AAA, AA, C, or D shapes). A 6V generator would also work, provided it can provide about 9-12W of power (this is a bit high for the average bike generator).

The parts you will need are:

=== POWER SOURCE ($20.11 US) ===
  • [DX sku.01251] - UltraFire WF-139 3.6/3.7V battery charger
  • [DX sku.19624] - 18650 3.7V 2400mAh lithium-ion protected battery (pair)
  • [DX sku.18074] - 18650 battery holder
  • Neoprene/velcro cell phone case (for the battery box -- something from the dollar store)
=== LIGHT ($29.20 US) ===
  • [DX sku.15084] - GU10 3-LED spotlight housing
  • [DX sku.02026] x 3 - SSC Seoul P4 (U-bin) LED emitter (buy three!)
  • [DX sku.05602] - Clicky switch
  • [DX sku.05031] - Silicone tailcap (glow-in-the-dark)
  • [DX sku.25516] - 5V~12V 9W 3*Cree 3-Mode circuit board LED boost driver
  • [DX sku.15234] - JST connectors
  • [DX sku.08274] - Universal bicycle mount
  • Two wood/metal screws, 10x1/2 plated steel, pan, button or round head (any hardware store)
  • Two small springs (scavenge these: in a pinch, you can use the spring from a pen and cut it in half, but if you can find a stiffer spring with a slightly larger diameter, it would work better. Springs from existing battery holders [e.g. for AA battery operated devices] can work well.)

=== TOOLS (if you don't already have them or can't think of a way to fake it) ===
  • [DX sku.22264] ($4.63) - 30W soldering iron (110V AC)
  • [DX sku.04593] ($2.14) - Heatsink thermal compound (20g)
  • [DX sku.04643] ($9.99) - 0.6mm Solder Wire (200g)
  • [DX sku.19908] ($3.39) - Diagonal cutters
  • [DX sku.46862] ($8.40) - Jeweler's file
  • Hot-melt glue gun (available at any hardware, craft, and many dollar stores)
  • Glue sticks
  • Small Phillips Screwdriver
  • Drill
  • Tweezers (beauty section of a dollar store)
  • Wires (cheap speaker wire is nice)

=== OPTIONAL TOOLS (you don't really need them, but they're handy) ===
  • [DX sku.23451] ($4.16) - 3 metres Black Heat Shrink Tubing - Five Size Pack (0.8/1.5/2.5/3.5/4.5mm)
  • [DX sku.51713] ($16.20) - Third Hand Soldering Stand with Magnifying Glass
  • [DX sku.21392] ($6.21) - Wire strippers
  • [DX sku.10018] ($12.07) - Digital multimeter (if you already have a multimeter, but it doesn't have a connectivity testing mode, you can just measure resistance. A resistance of nearly 0 Ohms is the same thing as a connection, which is the same thing as a closed-circuit, which is the same thing as a short circuit.)
  • Foil duct tape (available at any hardware store)
  • Metal file
  • Small pliers
  • Hot air blower or lighter (for the heat shrink)
  • Permanent marker
All DX parts can be purchased from . Prices there include worldwide shipping. You may be able to source equivalent (or better) parts for less money, or make substitutions, but I've provided the DX numbers to make things easy for those that just want to follow a detailed shopping list and know that all the parts will work together. When ordering the part numbers listed above, you'll end up with extra components, since some of them come in multiples.

Be warned: I have waited up to 4 months for parts to arrive from DealExtreme. I've always received my items, or received my money back if they couldn't ship it or shipped a wrong/defective item. But some times it's a long, frustrating process. They don't make you jump through hoops, but they can be extremely slow to respond.

They're pretty much a lousy retailer and unacceptable by any normal standards, but if you want to save a few pennies and not  leave your house, and you can afford to wait potentially forever, they might barely satisfy your needs. If you work at it, you can often find the same (or better) items on eBay for less money.
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bobcov1 month ago

Any chance you could publish any details of your on-paper new design? That way I could get the components and figure out a housing on my own. Thanks!

munkytec2 years ago
I have all of the parts that you've listed here (I ordered them a long time ago), but I'm missing one of the LEDs and it looks DX doesn't have it anymore (or at least I can't find it). Do you know of some other LEDs that would be compatible with everything you've listed here? I imagine I would need to buy a set of three again since it may cause some issues to use the two old ones and one new?
fryingwoks (author)  munkytec2 years ago
Sorry, link rot! I've fixed the links now. You can still by the LED from DX; just use the (updated) link in the above bill of materials list.

A word of warning: this light is really outdated now. I'll put together a new Instructable soon for a brighter, cheaper, more efficient, easier-to-build light. Even has USB charging.

That said, I haven't put together the new instructable because, while I've designed the new light, I haven't actually built it, because this old one is still working really great for me. It was bright enough a couple years ago, and my eyes aren't any worse now, so it's still plenty bright enough now!
Thanks for this nice instructable !
Did you have time to work on the update you were talking about ?
It'd be great, I'm also particularly interested in the USB charging...
dangmpls2 years ago
So I'm new to the world of these high power LEDs. An your previous discussion about using one XM-L T6 LED got me intrigued but a little confused, too.

Will it work if I use one of the newer LEDs [XM-L T6 885LM LED Emitter 6000K White Light Bulb (3.0~3.5V)] with a circuit board [5-Mode 1000mA 7135 Circuit Board for Cree and SSC Emitters] that says it can be powered by a single 3.7 volt cell, and if I hook the two 3.7 volt cells up in parallel rather than series?

Thanks for all your work on this.
fryingwoks (author)  dangmpls2 years ago
Short answer: yes, it'll work, and you can have it work quite well.

Putting Li-ion cells in parallel isn't generally recommended, but it's certainly possible if you're careful about it. (Google a bit to find some details about that.)

The simplest possible thing to do would be to just run a single 3.7V battery, and change it when it dies (instead of running in parallel). But that's less convenient in some ways (while saving you the hassle of worrying about matching cells).

A buck converter (a switched mode driver) is what I suggested in my previous comment about the XM-L. The 7135 is a linear regulator, and that circuit you quoted is designed to be used specifically in a design with a single LED powered by a single Li-ion battery.

If you wanted to use it in a differing design, you need to be aware of several things:

1) Dropout voltage: your power source must be at least some number of volts higher than the voltage required for your load. I think on the 7135 it's about 0.2V. e.g. to run your LED at 3.5V, your power source must be at least 3.7V. This shouldn't be a problem for the XML and a 3.7V battery. (Buck drivers have dropout voltage requirements, too.)

2) Any voltage higher than the minimum will turn into wasted energy when using a linear regulator (and depending on the actual circuit that you get, there is an absolute maximum voltage before it melts anyway). If you wanted to use a different battery configuration that results in a higher voltage, you'll just be wasting power. Running at 3.7-3.8V though, you'll see quite good efficiency.
Great. I didn't know what a buck driver was, but now I do. Will probably go with the single cell set-up, but will look into the parallel cell set-up (I'm guessing the downside is that the cells catch on fire!).

Will let you know how it turns out. Thanks again for the detailed how-to!
Mar HK3 years ago
I've had all the peices for this for a while, but (finally) put it together for the fall morning commutes, hours before the sun comes up. The bright setting is wonderful for the pitch black river valley, the medium is perfect for pothole detection on residential streets.

Enjoying this much more than the duct taped flashlight I used last fall.
-max-3 years ago
upgrade to a 1000 lumen xml t6 led. it is 100 lumens per watt @ 1000 lumens and 130 lumens @ 1W
fryingwoks (author)  -max-3 years ago
Yep! They weren't available when this was designed several years ago (nor really even until late last year), but you're right: it's better.

There's a GU10 housing that's the same as this one, only the lens is for a single LED. So if you use:

- Single-LED GU10 housing
- Cree XML LED
- And an appropriate buck driver (you wouldn't want a boost driver for a single LED)

You'd have a brighter, more efficient light, for the same price! And it'd be less work to build.

One lingering advantage to the 3-LED design is that you can use LEDs with three different colour temperatures in one light, to get a much better spectrum covered. So you could put in a 3W warm LED instead of one of the P4s.
how bright is that one you have? it almost looks brighter than my flashlight with the t6 led in it being driven by a 18650 battery
fryingwoks (author)  -max-3 years ago
How much current is your battery feeding the LED?

I can't measure lumens, but I can say:

At 1.5A, my XML-T6 is not as bright as this 3-LED design at 0.8A. (the 3-LED design is consuming more power, though, since it's running at over 10V)

At 3A, my XML is brighter.

I tend not to run either light at max power, though. They're both plenty bright enough for me (on street and in dark trails) on the lower settings.
whats the voltage to the t6 led? if it were driven at full power, 1000 lumens. what is the wattage on the 3 led light?
fryingwoks (author)  -max-3 years ago
I didn't already give you these numbers in the previous post because I only had a rough idea.

So now I've actually looked them up!

The XML is 2.7-3.3V over its current range. It's nominally 3.3V at 3A. Which is 10W.

The P4 is 2.9-3.8V over its range. At 0.8A, it's about 3.65V. So all three together, at high power, consume about 8.76W.
the t6 led has to be brighter... it uses more power and is more effectiant than p7s right? is the p7 a cree led?
fryingwoks (author)  -max-3 years ago
I'm not sure what you're referring to now.

Brighter than what? This instructable never mentions P7s. The full details of the components are all linked to in the first page.

LEDs don't "use" more power than each other. LEDs have specified operating conditions, and some LEDs have a higher maximum power rating than others. That doesn't mean that you have to run them at their maximum, nor does it imply that a higher power LED is brighter than a lower power LED.

If you feed two LEDs the same amount of power, the more efficient one, by definition, will be brighter.

If you feed a less efficient LED more power than a higher efficiency LED, you can balance it so that they emit the same amount of light (at their respective power levels).

If you want to know which LED is more efficient, you need to look at the datasheets for the specific LEDs and read the data. Manufacturers supply the datasheets online for their products so that you can compare them and see if they suit your application.

I believe that the XML is probably more efficient than a P7, though I don't know the specs for the P7. You can look that up. If that's the case, then at the same power, the XML will be brighter. I have no idea which has a higher maximum power.
i meant p4s is you mentioned on you last reply. i understand how leds work, i am talking about there max output. but i dont think 3V drives ether of the leds at full power, but the t6 is more efficient it the same current and thus, brighter. p7 led its Chinese and i have a hard time believing its 900 LM at the max. its 10 mm square. i think they saids it draws 15W.
fryingwoks (author)  -max-3 years ago
Please just look at the datasheets. They have the exact empirical numbers there. Arguing with me on the internet about it won't make them any brighter.
i found a few places to look at the brightnesses. they are also 100 lm per watt bat i dont know how bright they are.
nielvaish3 years ago
quick question!! can i use a only camera part of cell phone in other devices like in pc , rc car , etc........................................
fgerdes3 years ago
beautiful instructable!!! Quick question, i found an old dynamo w/ 6v 3w output. would the driver still work w/ such a lower wattage?
fryingwoks (author)  fgerdes3 years ago
Depends on a lot of things.

1) Lots of dynamos say 3W, but are able to put out more.

2) The driver will likely drop into low-mode, and may or may not be happy with your power source, but you'd really have to test.

3) For running off a dynamo, this design isn't optimal anyway, and you'd be better off running only one or two LEDs at a lower current, and doing it without a driver, but instead using a couple resistors, a supercapacitor (for a standlight), and some additional simple circuitry.

4) Alternatively, use your dynamo (with appropriate circuitry) to charge batteries, and use those batteries to power this light.
That makes sense...thanks for the advice and quick response! I'll try a couple different configurations and let you guys know how it turns out. Thanks again
hanelyp3 years ago
What kind of solder did you use on the LED board?
fryingwoks (author)  hanelyp3 years ago
Regular leaded solder.
t-bird3 years ago
Where did the circuit board come from that you put the LED's on? Was it part of the spotlight housing?
fryingwoks (author)  t-bird3 years ago
Yes, the housing comes with a PCB with pads for 3 LEDs.
Jeffromg3 years ago
Thanks for the inspiration and VERY nice instructable. I know a lot of time went into this and I appreciate your taking the time to put this together!