3W LED Hat Lamp - 300 Lumens

• Hands-free
• Dimmable with three settings
• Run times: 2-3 hours (high), 4-6 hours (medium), 20-30 hours (low)
• Uses 3 AA batteries
• Options for other LED colours

This hat lamp was inspired by ProdMod, who designed a 3W LED video camera light.

3W Hat Lamp

• 3W White LED
• 10 or 30 degree LED lens with holder
• Heatsink (2cm x 2cm)
• 2 pin connectors
• Heat shrink tubing
• Clear Epoxy

Battery Holder with Brightness Control

• 1 ohm 1/2 watt resistor
• 10 ohm 1/4 watt resistor
• 3 AA rechargeable batteries
• On-off-on switch
• 4 AA battery holder (with cover and on-off switch)

Hat Lamp Holder

• Hat
• Velcro straps

Tools

• Drill
• Scissors
• Dremel with grinding disc
• Soldering iron
• Hot melt glue gun
• Alligator clips (to hold parts when setting the epoxy)

Remove the contacts so that there is more space for the components. Use the last contact already soldered to a red wire to make this a three cell holder. The remaining slot is for the brightness control switch.

Drill a hole for the brightness control switch. A hot soldering iron may be used to enlarge the hole. Warning: When heating the plastic, do this in a ventilated area.

Wire the holder as shown.

This hat lamp uses two switches. The switch included with the battery holder is the power switch. The on-off-on switch combined with the built-in switch allows three different brightness settings.

If using red/yellow/IR LEDs, a 2-ohm resistor is required. It can be soldered to the LED externally if you plan on using different colours.

Brightness settings (for 3.8V 3W LEDs)
Direct drive - 1000mA
1 ohm - 500mA
10 ohm - 100mA

Note: The recommended forward current for 3W LEDs is 700 mA, but you can drive them a little higher. These LEDs usually have enough internal resistance for 3 AA batteries if you drive them directly. If using Luxeon Rebel and certain Cree emitters, you may need a minimum resistor value of 0.5 ohms for the high setting to limit the current to 1000 mA.

Mount the LED to the heatsink. I used JB weld and clamped it with crocodile clips overnight, minimizing the space between the base plate and the heatsink. To provide strain relief for the wires, glue the wire to the heat sink

2-pin connectors allow your lamp to be detachable, giving you the option to use other colours such as red for dark adaptation. You can also use it to select beam sizes.