These are instructions on building a very bright, very low power portable light for less than $100. I use these on my bike.

Step 1: Gather Parts.


64 16000mcd LEDs -- you can use other LEDs if you cant find these.
soldering iron
needlenose pliers
side cutters
4-5 dipole molex connectors
1 micromini toggle switch
1 type N or M DC connector. male and female.
a spool of approx. 26 guage wire.
a spool of approx 18 guage two strand wire.
4x2 project box
small (at least 2x3) circuit board, prefer through hole.
two part polyurethane resin
real rubber weather stripping
duct tape
2 lithium ion batteries and a charger for them

dremel tool
desoldering braid


I buy a lot of LEDs from these folks:

I bought my batteries from here:

I bought my resin from TAP Plastics in San Francisco:
http://tapplastics.com/ - Look for the "Quick Cast" two part resin.

Most other parts came from what I had laying around, or from the nearest RadioShack.

These lights take around 4-5 hours to build if you dont do these kinds of things all the time.

Step 2: Getting Started!

Heat up your soldering iron, and get out your LEDs and sidecutter.

I assume you're using LEDs with a 3.3v forward voltage drop. In fact, the entire project uses that assumption. Adjust your numbers accordingly if that's not true for you.

You will solder down 16 rows of 4 LEDs, so stuff the first row in to the board. You'll connect these positive to negative down the row, so make sure they all point the same direction.

Step 3: Flip the Board Over.

Stick your thumb over the LEDs and turn the board over. Bend the leads down so that your LEDs wont fall out when tacking them.

Notice how these are connected, you'll do this another 15 times.

Step 4: Cut Off the Soldered Leads.

Clip the soldered leads flush and bend the outside leads away from the row.

Next, bend your unsoldered leads down to the leads you just cut flush and solder them together.

Connect a 12 volt power source to each row when you're done soldering it. That way you know that each row works before moving on to the next.

Once you have 8 rows soldered down, your project will look similar to the photo for this step.

Step 5: Tie the First 8 Rows Together.

Bend the outside leads upward. Leave the top most leads long.

Cut the rest of the leads off and solder them to each other.

Step 6: Start on the Last 8 Rows.

Insert your next set of LEDs in between the rows which you've just soldered. The leads will be perpendicular to the first 8 rows, and the positive and negative leads will alternate being upward and downward. e.g:

+ - + -
- + - +

The LEDs may be a little hard to get in between your existing rows, but a little press with your thumb should send them in to place.

Experiment a little with this row before soldering, and it'll make sense.

Step 7: Solder Down the Last 8 Rows.

Connect each row to your positive and negative leads from the first 8 rows. You'll have to use a small tool to jump the negative lead for one of your outside LEDs.

Dont worry about insulating the leg you used to jump the negative lead, because you'll be casting this in resin at the end of the project.

Step 8: Attach Leads.

You're done with the hard part. Make sure all your LEDs are lit. Run your thumb over the solder joints for a bit and make sure they dont break. Resolder anything which comes loose.

Insert a couple of approx 26 guage wires through the LED side of the board and bend them over on the solder side. Connect up the long legs you left at the top of the board to them. Test the array again.

Step 9: Trim Down Your Board and Project Enclosure.

Cut your board down to size. I've seen people use a razor knife, a dremel tool, and tin snips for this. Find what works best for you. I prefer a razor knife and then a dremel tool for the final touch up. Knock the corners off the trimmed board.

Trim your project enclosure until you can get your board to easily rest on the shorter set of standoffs. Secure the board with toothpicks.

Step 10: Cast the Project in Resin!

This is a little bit tricky, so improvise as needed.

Block the section of enclosure off where you will place your switches. Dont drill the holes in until you cast the board in the resin.

Mix your resin and fill the enclosure up until the board is just barely submerged. Make sure to do this on a complely level surface. You cant go back once it's hardened, so make sure your light is working properly and that you like your board placement.

Step 11: Remove Cardboard and Toothpicks, and Allow the Resin to Set.

Wait until the resin has hardend just a little bit, and remove the toothpicks and cardboard.

Next, wait until your resin is completely set before moving the light to another surface.

Step 12: Drill Holes for the Switch and Power Connector.

Knock out the two exposed posts, and drill in the holes for the switch and power connector.

Solder them up and fold the wires aside. I like to keep a little length to them so that if I need to replace a switch sometime later, I have some extra wire to work with.

Step 13: Buff the LEDs and Close the Case Up.

Take a dremel tool or a soft cloth and buff off fingerprints of residue from the resin from the LEDs.

Cut a length of rubber weather stripping in half and line the edges of the light with it.

Fashion a cover for the front out of a sheet of 1/16" plastic or whatever else you might want to use. I've heard of people using plastic milk jugs as a diffuser as well.

Take a length of duct tape and tape down the cover to the weather stripping. This allows you easy access to the enclosure if you're on the road and need to work on a switch.

Step 14: Cook Up the Power Source.

I ended up settling on using surplus Lithium Ion batteries for this project. I use two 8 volt cells in parallel.

Apply flux to the battery leads and solder down your wires to the terminals.

A side note:

If you dont want to use these batteries, you can use conventional NiMH batteries. Your local electronics shop will carry holders for them.

While the LEDs are soldered to take around 12 volts at about 33mA, I found that I could drive my LEDs at a brighter output with around 16 volts at 41mA. Mess around with it.

Step 15: Modify the Battery Charger to Use Molex Plugs.

Open up your charger and attach two wires to the leads inside for use with your molex connectors.

Step 16: Make a Y Adaptor

Wire up a "Y" adaptor to connect from two batteries to the cable which plugs in to your new light.

Step 17: Attach Mounting Hardware to the Enclosure.

I pulled off a mounting bracket from an old bike light, and superglued it to the enclosure. You can do what you'd like with yours.

Step 18: Conclusion

You've just built a bike light which is brighter than most car headlights and weighs in under two pounds with batteries.


I'd love to hear from you if you build one of these, and would love feedback on how well it worked for you or any brilliant modifications you made.

Have fun!
This is Excellent! But, what about a dimmer for it?? any ideas? yhmmc@yahoo.com
Any "colloidal" material would work, powdered glass or tinted vinyl for example.
Where are your current limiting resistors or current limiting circuitry? LED's have to be operated at their specified current or their life will be greatly reduced. They won't limit current on their own - in fact it's very easy to burn them out if the current isn't limited. I think the only thing that's preventing this from happening with this circuit is the fact that the battery can't produce enough amperage to cook all of your LEDs. If you connected this to a power source that COULD supply more current the whole circuit would go up in smoke!
I think adding resistors to this array would actually be an easy added step to this process. You could just add one resistor to every one 1-2 LEDs and have em flush to the array and there you go.
You should never connect LED's in Parallel. They should be connected in a Series/Parallel circuit using current limiting resistors.
why not use a few high power leds?
Looking directly at the lit cluster it likely is brighter than many auto headlamps, however I question it's projection distance. Without a lens and reflector to better focus the light, it's more of an area illuminator instead of a beam projector. A couple of 3watt Luxeons, a reflector and even a lens of sorts would serve to REALLY be something a nighttime cyclist could benefit by.
Sort of off-topic, but you seem to be knowledgeable :-) I was wondering if there are bike dynamo/generator units with a converter to direct current? I've been planning GOOD frontlights to my bike but I hate charging at home and then switching batteries (and forgetting to do that). Also, I take riding as a physical exercise so I don't mind the extra payload to generate the current myself while riding the bike. My plan would be: - have one or more generators installed - those would charge a small battery to cover slow sections and traffic lights, maybe 1-2 minutes of full reserve power - a bloody mindblowing LED frontlight with a good reflector, capable of consuming enough watts that my lighting level would only ever be capped by my own foot power instead of e.g. voltage regulators at the dynamos. (A standard dynamo+bulb seems to reach the cap before I hit halfway of my cruising velocity.) How much of this could I buy off-the-shelf and how much building would it require? I don't mind tinkering but I have no idea of the size of the project. Is it feasible to even use these small generators to generate lots of power -- I know the efficiency won't be skyhigh but... high enough? thanks, ww
Ive seen small ones that are nothing more then a motor with a rubber wheel on the end that is in contact with with the wheel.
Rather than a small battery or hooking lights straight to a dynamo might I recommend a full fledged battery powered system? Still use the dynamos just buy a set of rechargables that will take the trickle charge, you may need to step down the current, but it is something I have been thinking about.
use a few of those stepper motors with a wheel on one end... and then mount the motors to your bike frame... and have the motors recharge a battery(or 2)... and then put a toggle switch on the handlebars...close to the thumb...(for easy access...) than hook the light up to the front of your bike... and house the wires (for the nice finished look...)and put a case around the batterys, motors, lights and reflector... the stepper motors from old floppy drives... batterys... depends on how long you want the light to last... and the wires are everywhere... you can even tear your walls apart and find some... and you might want a few regulators... and for a better one... you can add a high and low setting pretty easily... get a rocker switch... and hook half of the lights to the bottom one and the both of the lights to the top one... and then you can switch the power to high or low... hope this helps...
and you can mount half of the a quarter of the lights on the handlebars to let you have light in the direction that you are steering... and what i ment by a quarter of the lights is to have half of the over all lights mounted on the handlebars... and have only half come on when you have it on low...
<a rel="nofollow" href="https://www.instructables.com/id/EUMTL5CBVKEWZM48RO/">dynamo</a><br/><br/>an instructable for making dynamos<br/>
You can always use a medium-sized DC motor (try with your multimeter if you don't believe me)
Good idea! You can buy the generator from a bike light kit at kmart or somthing.... just make the LED hedlamp and put a battery on it. simple project motors used in reverse (not powered by battery, but powering the device) would work as generators.
I Need help creating a small LED display that I want to mass produce. Can anyone make suggestion as to who can help me build something like this? Please.....
I want to fix my old desk light with leds. It's one of those 12v ones. Will this work the same way. Output on the transformer is 50watts.
Also you don't have resistors thought that they are always needed.
wow...i love many leds!!!! they are right and small
Anyone know why they don't use something like this inside a Projector, instead of those super hot Xenon lamps. I would think that putting LED's in you can remove that stupid fan!!
Actually there are some (at least one) projectors using LEDs for the lightsource now, I don't remember the model but one of the major brands came out with one past spring. It was midrange "portable" model if I remember accurately. I think it still has a fan (LED still need the heat pulled away from them at high power levels), but if I remember the review it was a very small quiet fan, compared to other projectors.
Alex26i, they don't use leds in projectors because LEDs don't produce a full spectrum of light, while xenon etc. do. In a projector, you need the full spectrum for the colors to look right. And yeti, good job, I'm most likely gonna make this. Thanks X)
If you use the right materal you could blend the light togather to make a solid beam and make it seem like a light pannel on the frount of you bike or what you use it for. And a lense might make it a little brighter maybe?
in the top of a led, there is already a lense... so that is pretty unneccesary
perhaps you could use a larger lens to focus all the light coming from the little lenses on to one point. just a thought
Just curious... Is there any way to use the peddling-power of the human riding the bike to power the light (instead of using batteries)? Ben
you cold use any brushless toy motor as a generator for this including lego mindstorms
The downside of using a dynamo to power your lights is that, if you slow down and drop below the critical velocity (say on a hill or at traffic lights) you lose your illumination. You can use the dynamo to charger batteries but that's a more complex circuit.
There is, and it's done with a device called a dynamo. They're available in two forms.<br/><br/>The first is called a &quot;bottle dynamo&quot;, and it mounts on the fork and has a roller that contacts the wheel:<br/><a rel="nofollow" href="http://www.peterwhitecycles.com/images/products/Lights/ZinkensLT1.jpg">http://www.peterwhitecycles.com/images/products/Lights/ZinkensLT1.jpg</a><br/><br/>The second is called a &quot;hub dynamo&quot;. It's more efficient than the bottle dynamo, and it replaces the hub of your front wheel.<br/><a rel="nofollow" href="http://www.peterwhitecycles.com/schmidt.asp">http://www.peterwhitecycles.com/schmidt.asp</a><br/>
Great project! Do the LEDs get hot enough to cause any kind of fire concern? Thanks, Craig www.cahoonlawoffice.com
Great project! One question though. How much heat do the LEDs produce? Is there any kind of a fire danger? Thanks, Craig www.cahoonlaw.com
New cheap Nichia LED's and Luxon 1W-3W &amp; 6 watt LED's have high power smaller footprint and better power management... SMD devices can be a few cents each...or get 10 for free..<br/><br/><a rel="nofollow" href="http://vivalux.en.alibaba.com/product/50090690/50416001/LED_Modules/LED_Modules.html">http://vivalux.en.alibaba.com/product/50090690/50416001/LED_Modules/LED_Modules.html</a><br/><br/>Also get FREE samples from manufacturers upto 10 per order, LED, IC's and passives.<br/><br/>Cheaper than Ebay use Arrow, Avnet, Digi-key and buy bulk wholesale. China suppliers on Ebay can take 3-4 weeks to import and have poor quality.<br/><br/>
Ugh...better to calculate from Vf LED loads and Vd with LED's in serial configs, current limiting resistors are ok but better yet LDo or LED drivers...<br/><br/>(http://www.ngineering.com/LED_Calculators.htm)better to do the math. Do not exceed max V or mA raitings on the LED's this shortens life for brightness. better yet use a IC LED Driver for 80-90 efficiency, long battery life and LED's last tens of thousnads of hours.<br/><br/>
Ugh...better to calculate from Vf LED loads and Vd with LED's in serial configs, current limiting resistors are ok but better yet LDo or LED drivers...<br/><br/>(http://www.ngineering.com/LED_Calculators.htm)better to do the math. Do not exceed max V or mA raitings on the LED's this shortens life for brightness. better yet use a IC LED Driver for 80-90 efficiency, long battery life and LED's last tens of thousnads of hours.<br/><br/>
Inexpensive (< 20 USD) 40+ LED lights are popping up now that have bike mounts included. I was searching for LED lights on Ebay and ran across so many that I had to modify my search to exclude them !
Going by availability on eBay, this project can easily be renamed to 3,200,000mCd lights as there are 50,000mCd white LEDs available now. If you spend $40 getting 100 of those, you could even cut down the number of LEDs to 50 and still have much more light and make this more compact too. For 50 LEDs, the total power consumption shall be 4.5W. This would mean that a pack of 3 X 'AA' NiMH cells would theoritically last 2 Hrs!
You can rename this 3,200,000mCd light if you use the 50,000mCd White LEDs available on eBay for $40/100Pcs!
I built a similar light about a year and a half ago. I used 3mm ultra bright LEDs because I was able to aquire them for free. I made an array of 90 leds consisting of 30 parallel strings of three LEDs in series with a resitor on each string. I packed them tight like the above design and overheating has not been a problem. I wired three 3.7v lithium digital camera batteries together to create a 11.1v battery. I understand that this can be dangerous but so far I have had no problems. The board was mounted in a small radio shack project box with three push button switches on top. Each switch controls a bank of 30 LEDs for simple brightness control. My light was originally designed for mountain biking but due to the wide angle of the LED bulb the overall light was not focused enough for high speed. The light is amazing for night hikes in the woods or biking on the street. I am currently revamping the design with ultrabright 10mm 12 degree spot focused LEDs and a voltage step down circuit which will eliminate the need for most of the power robbing resistors. I will probably post an intructable on the next project.
Your gell cell was bad. 40W @ 12V is 3.3A, so a 10AH battery should last you almost exactly 3 hours.
Late reply here, but if anyone's browsing the archives, look up "Peukert's law", which talks about the efficiency of battery charging and discharging. Essentially, the faster you draw current, the less efficient the process gets. The battery's internal resistance burns off a lot of the energy as heat, so you see less power at the terminals. Each chemistry has its own Peukert coefficient, and it changes as a battery ages. Lead-acids are particularly affected by this, which is why they're usually rated at the 8-hour, or sometimes even the 20-hour rate. Nickel-Cadmium has the best Peukert performance of any common chemistry, which is why even modern power tools frequently use NiCd packs. They simply do better under sustained heavy load, and they hold up to hundreds of hard-use cycles, whereas a NiMH pack under the same conditions might be toast after a few dozen recharges. Check out batteryuniversity.com for tons of info.
the amp hour rating of gel cell batteries is not as simple as that. They're rated at some optimum load, and the actual current you pull out of them affects their performance: the more current you're draining the lower the _effective_ amp hours. So a 10 AH battery might last 25 hours at 0.5 Amps, and 3.3Amps might well drain it in less than an hour.
Im very interested in using this to create my home projector. I'm needing more info on using the switching regulator. Which regulator would I need? Thanks ll0ll ps : completely naive when it comes to electronics, but im tring to learn :o)
Heres some LED lamps I made years ago, some nice photos here.I havent updated my website for quite a few years, so looks awful lol<br/><a rel="nofollow" href="http://www.geocities.com/malc_hurn/index1.html">http://www.geocities.com/malc_hurn/index1.html</a><br/>malc<br/>
can someone make an instructable for a 5.3W bike-dynamo?? :D
The lumen output of 64 16000mcd 15&Acirc;&deg; LEDs should be about 55lumen<br/>Why didn't you use luxeon or lamina leds?-You can get a luxeon3 emitter(80lumen!!!!!) for 3.5$!<br/>I've built a portable light, using a 120lm luxeonV emitter (needs a small heatsink)<br/>take a look at <br/>www.lumileds.com<br/><a rel="nofollow" href="http://www.laminaceramics.com/">http://www.laminaceramics.com/</a> or www.mouser.com/lamina<br/>
If something isn't interesting enough, build it bigger. Great job.
Yeti, have you obtained any measurements of actual lumens? My understanding is that mcd cannot be directly converted into lumens, because lumens measure light energy flux falling on a surface. In particular, I'm interested to know how your led light compares to HID lights, e.g. the Light and Motion ARC lights.
or watts perhaps?
Could you post a schematic for the leds? And you list 72 led's but I only count 64 in your matrix.

About This Instructable




Bio: I'm a computer guy living in a computer world. I dream of making every object I touch daily myself. That's all.
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