LED Dimmable Lightbox

Build your 18W LED lightbox to fight the winter blues. This lightbox is diffused and dimmable using PWM. If you have a lamp timer, you can use it as an alternative to an alarm clock.

Step 1: Materials

LightBox

• 6 x 3W white LED
• Heatsink
• Metal box
• on-off switch
• 2.1mm DC power jack
• 12V 2A power supply
• Cable ties
• Epoxy putty
• Twist ties
• Plastic diffuser
• Epoxy
• Wires

Dan's PWM LED Driver

• 1 x NE555 Timer
• 2 x IRFZ44N N-channel MOSFETs
• 2 x 2N3904 transistors
• 1 x 0.01 uF ceramic capacitor
• 2 x 0.1 uF ceramic capacitors
• 1 x 50k potentiometer
• 2 x 100k ohm resistors
• 2 x 0.82 ohm 1W resistor
• 4 x 1N4148 diodes
• PCB
• PCB standoffs

Step 2: How Many LEDs Will I Need?

10,000 lux is often used for white light. Lower lux levels are useful, although you need longer times. For green light, 350 lux is equivalent to 10,000 lux of white light. One lux is equal to 1 lumen per square meter. Note that diffusers also block light. A lux meter would be useful.

Lux/Lumen Converter
http://www.ledrise.com/shop_content.php?coID=19

Step 3: LED Driver

I used this driver because it allows PWM dimming. For power supply voltages above 15 volts, the gates and 555 timer will need a voltage regulator. You can use the LM7812.

Step 4: Mount LEDs to Heatsink

Mount the LEDs with epoxy.

Step 5: Cut Holes in Box

Cut holes for the DC power jack, screws, switch, potentiometer, and heatsinks.

Step 6: Cut a Square for the Cover

Step 7: Attach Diffuser to Lid

Cut the diffuser to size and drill mounting holes on both the metal lid and the sheets.

Step 8: Sand the Inner Surface of the Box

Step 9: Wash Metal Box

Wash the box with soap and water to remove metal shavings.

Step 10: Mount Components to the Box

Mount the heatsinks, switch, and DC power jack with epoxy putty.

Step 11: Enjoy the "Sunshine"