The Ultimate Power LED Head Lamp

This Tutorial shows you how to build a 8 Watt, 500+ lumen LED powered headlamp. It is a great alternative to buying a brand name headlamp, which is much more expensive. Lets start with the specifications of the finished product followed by the required parts.

1. Spesifications

1. Brightness: 500+ lumens / 7 million+ mcd @ 15 degree
2. Weight: 120 gram headlamp + 60 gram electronics + 280 gram battery pack = 460 gram total.
3. Cost: $60, including the batteries
4. Battery Lifetime: 3, 6, 12, 24 hours (4 brightness settings)
5. Size: Headlamp portion is aprox. 5cm x 5cm x 2.5cm
6. Rechargeable batteries: Ni-MH or Lithium-Ion batteries (your choice)
7. Unbreakable: Great LED technology

Figure 1: LED Lamp on one of my friends helmets

2. Collecting Materials

1. 4 x Luxeon Star 1W Cyan (LXHL-ME1D or LXHL-ME1C) OR Green (LXHL-MM1C or LXHL-MM1D) - (the circuit will work just fine with any color LED you want)
2. Old CPU heatsink (around 5cm x 5cm x 1.5cm)
3. LED Dynamics Buckpuck (3021-D-I-1000 or 3021-D-E-1000)
   
4. LED Dynamics Buckpuck (3021-D-I-1000 or 3021-D-E-1000)
5. 4 x L2Optics/Dialight OP-015 lens
6. 4 x L2Optics/Dialight OH-ES1-CL lens holder
7. 8-10 x AA NiMH rechargeables, or 3 x Lithium-ION rechargeables
8. 2 small toggle switches (digikey 519PB)
9. 1 large toggle switch (digikey 514PB)
10. Flexible stranded wire
11. Sheath for wire (eg: sheath of a 3/16" double-braid rope)
12. Silicone or epoxy
13. Thermal compound (also known as thermal grease or heatsink compound)
    
14. Plastic or fiberglass for heatsink mount
15. Old headlamp headband

Figure 2: Ingredients

3. Solder the LEDs together

Start by soldering the Power LEDs together so that they fit on the heatsink. The LEDs are in a series-parallel configuration (see below). This means 2 LEDs in series, 2 pairs of that are in parallel)

Note: If you want to make a white headlamp (or any other color for that matter), the project will work exactly the same.

Figure 3: Power LED Circuit (Note polarities)

4. Apply heatsink goop

Next, firstly clean the heatsink thoroughly so that glue will stick to it later.

Then apply the heatsink goop (hightech name is heatsink compound a.k.a.thermal compound a.k.a. thermal grease) to the bottom of LEDs. They will probably have aluminum underneath. You can also use thermal "glue " instead, but it is hard to find and a bit pricey.

Stick LEDs onto the heatsink and wiggle them a bit (but remember to keep the goop from getting all over the heatsink since you will need to have the glue stick later).

Figure 4: The thermal compound (or Goop)

5. Glue on the LEDs

The glue is all I used to hold down my LEDs. It seems sufficient enough and is quite tough and durable to me. However, if you are worried, the alternative is to drill 2 holes for each of the LEDs into the heatsink (matching the cutouts in the star), and bolt them down with 4-40 size (or 3mm size) nylon machine screws. These are available from www.mcmaster.com.

Tips:

1. Do not get any glue on the LED lens! Some glues (like silicone) you can get off the lens after it dries, but uthers are to hard.
2. Make sure the glue can handle 80-100 degrees celcius. The LEDs get pretty hot. (Don't use hot-melt glue!). Also, make sure it is waterproof (don't use superglue)
3. I used silicone as a glue, but if I do it again, I will definitely try epoxy instead. The silicone does not flow by itself and this makes it hard to get it to fully cover the LEDs (in order to have a submersible waterproof lamp). With epoxy you can dispense it with a syringe and so accurately get it everywhere but the lens. Smearing the silicone around was a messy job!
4. After applying the glue, press the lenses and their LEDs in place.
5. Remember to test the LEDs again before the glue is hard.
   

Figure 5: The glued setup

6. Attach the buttons to the Buckpuck

Again hot-glue or silicone works. The big switch I used for the master on-off switch. The smaller ones will control the brightness of the LEDs. You actually need only TWO small switches (three was a bit too much turned out to be overkill).

Figure 6: The glued buckpuck buttons

7. Solder on the "brightness" resistors

Refer to the photo below. We will be building it by using "point to point" wiring/soldering.
Resistor values (and colors)

• R1 = 680 ohm (blue gray brown)
• R2 = 1200 ohm (brown red red)

The above values worked for my buckpuck (despite a somewhat misleading note in the datasheet). I encourage you to test your resistor values before soldering.

These resistor combenations give you FOUR overall power settings:

1. both switches off: full power
2. one switch on: 1/2 power
3. other switch on: 1/4 power
4. both switches on: 1/8 power

Soldering notes: These particular switches are made from fairly crappy plastic so make sure you solder them quickly. If you heat them too much for a long time they will melt inside and not work properly anymore. Follow these steps to solder them without overheating them:

1. Heat the resistor's lead and melt a small blob of solder onto it (called "tinning" it)
2. Heat the switch lead and do the same
   
3. Hold the switch lead against the resistor lead and melt the two solder blobs together, without needing to add any new solder.

This is good soldering practice. In general, you should follow this technique anytime you are soldering something together that is heat sensitive (such as the battery holders).

Figure 7: The resistors thet control brightness

8. Assemble the headlamp

And now the fun part, assembly. For this you will need an old headlamp strap and mount (or you could make one yourself from plastic and a bungee-strap). You'll have to figure out the best way to attach your heatsink to your headlamp, since it depends on your component choice. For my lamp, I cut two simple pieces of plastic to make everything fit (see below).

Figure 8: Assembly of the heatsink and lamp strap

9. Do the wiring

First, I covered the entire wiring (from LEDs to batteries) with a sheath from a 3/16" rope. If you've used very durable wire this step is not for you.

Next, I made a so called "strain relief" where the wires are attached to the headlamp. This is to prevent the wire from getting tangled or ripped when the battery is dropped, or the lamp angle is changed.

Make an normal overhand knot in the wire. Now glue it to the base plate like in the photo. The knot gives better grip to the wire sheath and the glue.

Figure 9: I used a LOT of glue

10. Make the battery pack

The "Buckpuck" I used lets you use pretty much any battery pack. The buckpuck is just an very efficient (90-95%) DC-to-DC step-down converter that ensures an correct outputs (voltage and current) to the LEDs, no matter what the input voltage is. The power LEDs may need up to about 7V to run them, and you'll need to add 2V more for the Buckpuck. This means any battery pack above 9V will work. I used 8 x NiMH cells that give 9.6V. Other combenations include 3 x lithium-ion cells (11.1V) and 10 x NiMH cells (12.0V). All good choices.

I used AA size batteries. These are 2700mAh cells, which yielded an output of about 3 hours runtime at maximum power, and 24 hours runtime at minimum (1/8) power.

Figure 10: Nice and neat

11. Finish the wiring and test!

Fix the final wires to the buckpuck.

Figure 11: Final step, wires

The lenses just press-fit into the lens holders. Several different lenses are available for these standard mounts, so you can choose the angles you want.

Figure 12: If you think this looks good, wait till you switch it on!

Don't stare directly into the light! It will blind you!



Listed under leds