Race proven! I put the light to the ultimate test by competing in the Gold Rush 24-hour Adventure endurance race in the Sierra Nevada mountains of California. Many of the other competitors had $500 HID lamps from NiteRider, Light & Motion, etc, yet throughout the race nearly everyone that saw my light commented as to its extreme brightness or asked where they could get one. It was that much brighter than anything else.
brightness: 500+ lumens / 7 million+ mcd @ 15 degree
weight: 120 gram headlamp + 60 gram electronics + 280 gram battery pack = 460 gram total
cost: $60 including batteries
lifetime: 3, 6, 12, 24 hours (4 brightness settings)
size: headlamp portion 5cm x 5cm x 2.5cm
rechargeable: Ni-MH or Lithium-Ion batteries (your choice)
unbreakable: LED technology
- Cyan (or Green) high power/high efficiency LED's
- high-transmittance TIR lenses
- high-efficiency DC/DC step-down converter
None of this was possible just a couple years ago, but now it can be done easily with inexpensive components you assemble yourself!
i've got several other power-LED instructables too, check those out for other notes & ideas.
This article is brought to you by MonkeyLectric and the Monkey Light bike ilght.
Step 1: What's so special here?
(1) The rods are about 2.5 times more sensitive to light than the cones. That's why they are your night vision.
(2) The rods and the cones are not equally sensitive to all colors (wavelengths) of light. The wavelength of maximum sensitivity for your rods is 507nm, or blue-green. Why? Moonlight is more bluish than sunlight. The color of maximum sensitivity for your cones is 555nm green, about the color of plants. (more info)
To get the best possible vision at night, we'd like to build a lamp that puts out the most light at the 507nm that our rods are most sensitive to. This gets us the best vision at night for the least power used. If we had a white light instead, it would take much more power to get as much visibility.
Thanks to our friend the LED, this weird pure turquose light is possible! The latest LED technology is much more efficient than a standard light bulb to begin with, but using the special turquose color gives us even much better night vision than white, and is more efficient than even the fanciest HID lights.
Step 2: Ok, but really what is so special here?
1) use cyan or green LED's. these will give 2.5x their rated lumen output using your night vision, because they are rated based on your day vision. (see http://hyperphysics.phy-astr.gsu.edu/hbase/vision/bright.html )
2) use the latest high-power LED's. new LED's such as the Luxeon's are rated about 50 lumens/watt for cyan and green (this is the day-vision rating). this is equal to the high-end HID lamps and at least twice as efficient as a halogen lamp. The Luxeon LED's used to be pricey, but now they are about $3 each.
3) use the latest optics custom-designed for the Luxeon LED's. several companies are now making low-cost lenses for LED's based on the TIR (total internal reflection) principal. These lenses do not have a reflective mirror, and achieve 85%-90% transmission. non-LED lamps lose much more of the light because some of the light shines backwards where it can't be used, and because mirror reflectors are less efficient. typical transmission for reflector-based systems is only 65%.
4) don't over-power the LED's. looking at the LED datasheet, we notice that the LED efficiency goes down somewhat with higher power: 45 lumens at 1W power, but only 80 lumens at 3W power. so we get the best efficiencies with less power. this indicates the importance of having a brightness-switch on the unit. in practice i have found the 1/2 power setting to be nearly as bright as the full power setting.
Step 3: What you need
old CPU heatsink (around 5cm x 5cm x 1.5cm)
LED Dynamics Buckpuck (3021-D-I-1000 or 3021-D-E-1000) - $20
4 x L2Optics/Dialight OP-015 lens - $1 each
4 x L2Optics/Dialight OH-ES1-CL lens holder - $0.30 each
8-10 x AA NiMH rechargeables, or 3 x Lithium-ION rechargeables - $20 total for NiMH
2 small toggle switches (digikey 519PB) - $1.50 each
1 large toggle switch (digikey 514PB) - $2
flexible stranded wire (18ga to 22ga)
sheath for wire (eg: sheath of a 3/16" double-braid rope)
silicone or epoxy
thermal compound (also known as thermal grease or heatsink compound) - $5
plastic or fiberglass for heatsink mount
old headlamp headband
Where to get it:
old CPU heatsink - you will find these in any broken computer from 1995 onwards. in newer pc's the heatsink will be too large, but you can cut it with a hacksaw.
the LED's, lenses, and buckpuck all come from future electronics also see here - the 2nd link is a direct search for the LED's and buckpucks. for the lenses, here is the direct search to find them.
You can get the above LEDs, buckpuck & maybe lenses at farnell.com or rswww.com
- i recommend Luxeon 1W Stars, either Cyan or Green with either Lambertian or Batwing type. My testing shows that the 1W stars can be driven at 2W no problem with the heatsink, and they are much easier to work with than 3W stars because their backplate is insulated.
- Several different lenses are available for the lens mounts, so you can easily tailor the light to your needs. you can even change the lenses on the road in a minute or so. there are 5 degree, 15 degree, 25 degree and 5x25 degree lenses available, all are $1 each.
batteries are from http://www.batteriesamerica.com
switches from http://www.digikey.com (probably can find similar items from future electronics)
small quantity thermal compound. both computer and electronics stores have this. "Arctic Silver" is one of the common ones for computer use. Thermal adhesive is even better if you can find it (and it is pricey).
http://www.mouser.com (search for "thermal compound")
http://www.newegg.com (search for "thermal compound")
Digikey also has it, but only in $25 packs. CompUSA also will likely have it.
wire: 22ga is ideal here. you want something flexible that won't break after a few flexes. this can be surprisingly hard to find! radio-control hobby stores usually have something like this. at Home Depot you can get an 18/2 or 18/3 rubberized cable ("SJOOW") and split it open to get out the individual wires.
sheath: you want something to go over the wires and protect them. a good choice is a 3/16" or 1/4" double-braid rope (that means it has a core and a sheath). you pull out the core and have a sheath left. you can probably find this at Home Depot, if not try your local Marine store for yacht rope.
more information: the technical datasheets for each component:
Phillips Luxeon Star Led's: http://www.luxeon.com/pdfs/DS23.pdf
Led Dynamics Buckpuck: http://www.leddynamics.com/LuxDrive/datasheets/3021-BuckPuck.pdf
L2Optics/Dialight Lenses: http://www.l2optics.com/luxeon.aspx
Step 4: Solder the LED's together
note that if you want to make a white headlamp, or any other color, the project will work exactly the same.
Step 5: Heatsink goop
apply heatsink goo (heatsink compound aka thermal compound aka thermal grease) to bottom of LED's. you can also use thermal glue instead (and it is probably better if you do), but it is hard to find and a bit pricey.
stick LED's on the heatsink and wiggle slightly (but keeping the goop from getting all over since you need to have the glue stick later)
Step 6: Glue the LED's
1) do not get any glue on the LED lens. some glues (like silicone) you can get off the lens after it dries.
2) make sure the glue can handle 80-100 degrees celcius. (don't use hot-melt glue!). make sure it is waterproof (don't use superglue / cyanoacrylate)
3) i used silicone, but if i do it again i will try epoxy instead. the silicone does not flow by itself, so it is hard to get it to fully cover the LED (in order to have a submersible lamp). with epoxy you can dispense it with a syringe and accurately get it everywhere but the lens. smearing the silicone around is messy.
4) after pouring the glue, press the lens holders into place on top of the led's
Step 7: Attach buttons to buckpuck
the big switch is the master on-off
the small switches will control the brightness. you only need TWO small switches, three turned out to be overkill.
Step 8: Solder brightness resistors
R1 = 680 ohm (blue gray brown)
R2 = 1200 ohm (brown red red)
these values worked for my buckpuck despite a somewhat misleading note in the datasheet, so test your resistor values before soldering.
these values give you FOUR overall power settings:
- both switches off: full power
- one switch on: 1/2 power
- other switch on: 1/4 power
- both switches on: 1/8 power
1) heat resistor lead and melt a small blob of solder to it ("tinning" it)
2) heat the switch lead and melt a small blob of solder to it also
3) now hold the resistor lead against the switch lead and melt the two solder blobs together, without needing to add any new solder.
this is good soldering practice in general anytime you are soldering something that is heat sensitive (such as the battery holders)
Step 9: Attach headlamp
Step 10: Strain relief the wiring
first, i covered my entire wiring with a sheath from a 3/16" rope. if you've used very durable wire to begin with this may be overkill.
next, i made a strain relief where the wiring attaches to the headlamp, so that it won't get tangled or ripped when the lamp angle is changed, or the battery is dropped.
make an overhand knot in the wire, then glue it to the base plate. the knot gives much better grip to the sheath and the glue.
Step 11: Make the battery pack
I used 8 x NiMH cells, AA size. These are 2700mAh cells, which yielded about 3 hours runtime at maximum power, and 24 hours runtime at minimum (1/8) power.