Curiously Strong Bike Light - 400 Lumen Cree LED ALTOIDS

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Introduction: Curiously Strong Bike Light - 400 Lumen Cree LED ALTOIDS

About: Fat, old, and nearly bald, Pat O'Briant bumbled his way through an aeronautical engineering degree at an enormous state university which fortunately had an open admissions policy. I've spent the last 28 year...

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.

Step 2: Assemble the Internal Components

Bolt the mounting bracket to the bottom of the tin.

Insert a 4 x AA battery holder.

Insert the Buckpuck dimmer switch and bolt in place.

(The BuckPuck is the postage stamp size block in the picture. It accepts power from 5 to 32 volts and outputs the constant current high power LEDs like. The dimmer is a potentiometer switch which controls the brightness of the LEDs and comes prewired with the 3023-D-E 1000P Wired BuckPuck.)

Step 3: Parallel Vs Series Connection of the Star LEDs

Use the parallel connection for 4 batteries (6 volts). For higher voltage battery packs I recommend the series connection.

Step 4: Solder the BuckPuck and LEDs in Parallel

The Cree XR-E Star LEDs have very wide solder tabs, clearly labeled + and -. For the battery pack shown (less than 6 volts input into the buckpuck) wire the LEDS in parallel. If you have a higher voltage input you can wire the LEDS in series as shown below.

Step 5: Epoxy LEDs to Altoid Tin

Solder wires from 4 AA battery holder to Buck puck wire.

Apply epoxy to the back of the soldered LEDs and hold in place until solid. Arctic silver thermal epoxy is probably best as the Altoid box will act as a heat sink, but I have also used standard household repair epoxy and not experienced overheating with the Cree LEDs.

Step 6: Epoxy Optical Lens, Insert Batteries and Power-on

Epoxy plastic optical lens over LEDS. Try not to get epoxy on the LED lenses. Hold in place until firm.

Insert 4 rechargeable NiMH AA batteries.

Turn the Dimmer Switch to on and mount on bike. Enjoy the night.

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    35 Comments

    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.

    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 ?!

    1 reply

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

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

    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.

    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.

    1 reply

    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.

    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...

    4 replies

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

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

    Wow, it works great. Thanks.

    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.

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

    3 replies

    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).

    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!

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

    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?

    3 replies

    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.

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

    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.