Curiously Strong Bike Light - 400 lumen Cree LED ALTOIDS

Build a 400 lumen bike light in an Altoid tin for ~$50. The new incredibly bright, high efficiency LEDs by Cree, the Cree XR-E are simple to wire and are relatively cheap. Drawing very little power but able to output 100 lumen each at 350 milliamps and an incredible 200+ lumens each at 1000 milliamps these little LEDs are at least 30% brighter than last years best Luxeon LEDs. Power for 2 or more hours with 4 AA NiMH rechargeable batteries. Everything tucks neatly into an Altoids tin. Ride bright and never fear the dark again.
Parts List
- 2 x Cree XR-R Star LED (LEDSupply.com 2 x $8.49)
- 1 x 3023-D-100 Wired BuckPuck, 1000mA Output (LEDSupply.com $19.99)
- 1 Altoid Tin
- 1Minoura Mounting Bracket (for water bottle cages) (Nashbar.com $3.50)
- 1 Plastic 4 x AA battery holder (Radio Shack $1.50)
- 4 x AA rechargeable NiMH Batteries (multiple sources ~$7)
- Cree L2 6 degree optical lens (LEDSupply.com 2 x $2.00)
(others - solder, solder iron, 5/64 drill bit, drill, artic silver epoxy (preferred), LEDSupply.com )

Step 1 Drill 4 holes in your Altoid tin

Drill 2 holes in the bottom of the tin to mount the bracket which will hold the tin to your handle bars.

Drill 1 hole on each side, 1 for the wires to the LEDs and one hole to mount the dimmer switch which will control the LEDs.

Comments

[mtaylor22]

Thanks a lot. I have been looking around at home-made lights and wondered what a "buckpuck" was as it was mentioned in some forums. I thought of using a guitar pot. switch but figured it probably would be the wrong sensitivity, and cheap ones are staticky. Great find. How do you feel about the LEDs with no reflector on them? Looks like it works ok, though. Good job.

[pteranosaur]

Me thinks you say-use the paralell connection for 4 batteries(6vdc),for higher voltage,use series connect...Will not the paralell connection only give 1.5vdc ?!

[mtaylor22]

He surely means the LEDs are connected in series or parallel, in the above post, as shown. The batteries are of course in series.

[eterzi]

I got the the 3023 D-N-1000 on accident... will this be ok?

[Entropy512]

Running LEDs in parallel without individual current limiting for each series strand (in this case, your series strands are just single LEDs) is a bad idea - If one LED fails or disconnects, the other LED will receive all of the current and be overdriven. LuxDrive also sells the BoostPuck, which would allow you to drive a 2-series LED array from 4xAA.

[lolzertank]

Doesn't the buckpuck require a higher input voltage than its output voltage? So even though the buckpuck can operate from 5 volts or possibly a little less, your leds have a forward voltage of 3.7V each at 1000ma for a total of 7.4V since they're in series. With each led getting less than 2.5V, there is no way they are operating even near 350ma, much less 1000.

[swamp_yankee]

Read the datasheet. As you say it can operate down to 5V, but the output is a current (as specified in the part #) and the voltage can exceed the input voltage, up to a max of 32V. This is known as a "boost converter". Current drawn from the lower voltage input is higher than the current to the higher voltage output. Go to zetex.com and look at the datasheet for ZXSC300 or ZXSC310 for actual schematics of how this works.

[outfieldman]

I just finished soldering up everything, and I have two quesions. first, it seems that the lens needs to sit flush against the led for proper placement of the light, but the solder is in the way of letting the lens sit flush to the light??? Also, the light really isn't very bright; both bulbs are on, but the dimmer really just works as an on-off, and its not that bright. Thanks for any help on this...

[outfieldman]

Thanks. Would it be possible for you to add a schematic or photo as I don't know anything about wiring. Thanks!

[pobriant]

outfieldman, No problem. Let's see what I can do. There are many ways to complete this little circuit but here is one option.

[outfieldman]

Wow, it works great. Thanks.

[pobriant]

Outfieldman, My apologies for not having corrected this sooner. Step 3 is incorrect, the LEDs should be wired in parallel not in series as shown in the picture. And you are absolutely correct that the lens should be flush with the lens. If you are very careful and only apply a thin strip to the solder pads of the star leds I believe the lenses should glue flush. The lenses are plastic and quick work with a file or a dremel tool grinder wheel might correct any issues. Again my apologies and good luck.

[hammertong]

Does the dimmer come with the buckpuck? What potentiometer would you recommend?

[pobriant]

hammertong,
Sorry for the long reply. Ledsupply,com offers buckpucks with and without the potentiometer. Model http://ledsupply.com/03023-d-e-1000p.php (newly raised to $19.99) comes with the potentiometer, model http://ledsupply.com/03023-d-e-1000.php (now $15.98) comes with the control wires for a potentiometer or resistor but none attached. Without a pot or resistor the buckpuck is full on. If you just want full on/off this would be simplest. The pot appears to be a standard 0-5k potentiometer allowing current control of the buckpuck, Mouser.com sells this for $1.38, partnumber 31JN305-F but i have not tried it (Digikey should work as well). For biking on trails with oncoming pedestrians and bikes, I wanted a simple high beam / low beam switch so I replaced the potentiometer with an on/off switch in series with a 360 ohm resistor. On = 360 ohms resistance across the gray and yellow buckpuck control wires = low beam, off=open = high beam. (To turn off, there is a second switch on the power to the buckpuck).

[hammertong]

I just got my shipment from LEDsupply today and was glad to see the dimmer switch prewired. I then soldered everything together and thought my rechargable AA's were dead, then realized I put the jumper wire on the wrong polarities. + in & + out to - in & - out. I swapped it and the light works great. Great Instructable, awesome (and simple) design. Thank you!

[pobriant]

hammertong, Fantastic. Thanks so much for your feedback. I appreciate that very much.

[goodgnus]

Interesting... I wonder what kind of heat those babies generate and if you maybe should have had some intermediate heatsink between the LED's and tin. How hot does the tin get around the LED's after it's been running for some time?

[pobriant]

Outstanding question and got me thinking I should try to measure the temperature. I stopped by the local RadioShack tonight and got a 10k ohm thermistor and copper taped it on the back of a spare Cree LED Star sitting on a wood bench. I figured this would be pretty close to worst case, no extra airflow from riding, no heatsink at all from the Altoids tin. I measured the resistance after half an hour (seems to be steady state) and read 2.66k ohms and the fine Radio Shack conversion puts this at around 63 deg C (plus or minus 5%). Cree's spec sheet states "LEDs to maintain an average of 70% lumen maintenance after 50,000 hours, provided the LED junction temperature is maintained at or below 80ºC." The back of the Star may be cooler than the LED junction, but I think it is probably ok. No guarantee.

[clark]

when i went to radioshack a few weeks ago they told me they didn't have themistors! where did you find it?

[pobriant]

clark, Thanks for pointing this out., RadioShack cat. # 271-110A- 10 kOhm @ 25 degC. , was the unit I found in their bins. I just checked Radio Shack's website and it does not show up. Sorry. Digikey or Mouser might be your best bet.

[clark]

i got one at mouser, it worked for what im using it for.

[QuiksilverRox]

I thought LEDs don't produce heat, just light.

[jmengel]

As "goodgnus" says, the heat is still significant. It just shows how inefficient the incandescents are. If a typical incandescent is 2% efficient in terms of visible output (~12 lumens/watt), then a 100W bulb puts out 98W as heat (Easy Bake oven brownies anyone?) and other wavelengths. The best LEDs are in the range of 120 lumens/watt, which is roughly 10x the efficiency of an incandescent or 20% luminous efficacy. So a 3W LED still puts out about 2.4 watts of heat and other waste wavelengths. This need to be dissipated to keep junction temp down and luminous efficiency and lifetime up. So, yes LEDs output a lot more light compared to incandescents, but the heat output still dominates.

[goodgnus]

LOL. I do suppose we all start at 0,0. Led's certainly produce heat. At low power it is less detectable and certainly less heat than a comparable incandescent would generate. However, todays high power led's produce significant heat.

[malkari]

yea its brill,be nice to see the wires a bit better from the battery and petentiometer to buckpuck.

[pobriant]

Thanks for the suggestion, I'm currently waiting on parts from dealextreme for version 2.0 and I will try to include better pictures of the wires. Dealextreme does not always have everything in stock and the shipping is from Hongkong but their prices are worth the wait in most cases.

[szaballos]

Can you run more than two Cree's off this buckpuck while connected to the 4.8v source?

[pobriant]

szaballos,
If you parallel the LEDs instead of wiring in series the answer is yes, The disadvantage is you are reducing the current and reducing each LED output. The star LEDs have 2 positive solder pads and 2 negative pads making parallel connections easy so you can experiment and find the optiminum configuration.
For LEDs in series like I show in step 3, the answer is no. The LEDs will not run. Two is the limit for 4.8 volts with a series connection. Most of these high power LEDs (Cree, Luxeon, etc.) need a threshold of 2.3 volts to run (but not more than 3.9 volts or they lose life quickly). So 4.8 / 2.3 = 2 LEDs maximum in series is the maximum for a 4.8 volt driven buckpuck.
Dealextreme sells drivers that both step voltage up and regulate current, allowing high power LEDs to work with one 1.2 volt battery. examples shown here;
http://www.dealextreme.com/details.dx/sku.15880
http://www.dealextreme.com/details.dx/sku.7302
http://www.dealextreme.com/details.dx/sku.4735
Or If you want to stick with the buckpuk but want more light, I recommend stepping up to a higher voltage battery pack. The 3023 buckpuck can handle up to 32 volts. Unfortunately more than 4 AAs is a tight fit in an Altoid tin and the run time of AAAs is just too short. An empty water bottle makes a good battery case, and the cordless drill packs work well too. The Dewalt 36 volt lithium is really only 10 cells yielding a nominal 32 volts and I have used it with a buckpuck and 12 luxeon LEDs. But in my opinion, 12 LEDs may be a bit too bright for oncoming traffic. Good luck.

[Ledgehanger]

Would you please forgive my ignorance and answer a simple question for me? When soldering the AA battery holder to the buckpuck, does it just require attaching black to black and red to red? Thanks.

[pobriant]

Ledgehanger, Yes red to red (positive), black to black (negative). I like to solder and then add shrink wrap tubing to insulate but a wrap of electrical tape will also work.

[krupan]

Any thoughts on whether one of the smaller cheaper LED drivers would work?

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

I'm worrying that the min. input voltage for the buckpuck is 5V and 4 NiMHs don't quite add up to 5V. And I'm cheap...

[pobriant]

Krupan,
Also Check out
http://www.dealextreme.com/details.dx/sku.7612
I share your concerns about the voltage of NiMH Batteries. Typical individual NiMH batteries fully charge to around 1.4 volts but drop to 1.2 volt. And of course 1.2x4 is only 4.8 volts. The buckpuck states the minimum voltage as 5 volts but mine appears to still work at a little lower voltage ~4.6 to 4.7 volts. (But I'm also very cheap as well. The micropuck listed first may not be able to drive multiple high power LEDs and the bucktoot in your second link States the same 5 volt minimum as the Duckpuck. My Altoids Version2.0 will likely use either a single LED with a single Deal extreme driver or multiple Drivers with one LED per driver. I really like the Dealextreme prices.

[sarubin]

Great fabrication. Could you please check the name/spec of the Cree lights and buck puck listed on the front page? They are different than that available at LEDSupply and different from what you state in the next steps.

[pobriant]

sarubin,
Hope this is more complete then the abbreviations above;
White Cree Q4 XR-E Star at http://www.ledsupply.com/creexre.php, note that these are rated 100 lumen at 350 mA, but I drove them at 1000 mA with the buckpuck below,

3023-D-E-XXXP: 1000mA Constant Current Output, External Dimming w/ pot. The pot appears to be a standard 0-5k potentiometer allowing current control of the buckpuck. ( note - An option to save $4.00 and possibly improve the control is to buy the same device without the potentiometer 3023-D-E-XXXX: and control with a 3 way switch, open or wires unattached = full-on 1,000 mA, with a 5k resistance = full off, and ~360 ohm resistor = 100 mA which in my opinion is a nice be seen light / low beam option). Or in other Instructables find your own "how-to" build your own circuit control for LEDs and eliminate the buckpuck entirely. Your mileage may vary.

[heavypiece]

Dude...that is such a cool set-up... 400 lumen from an Altoid tin. Great idea.