Instructables
Picture of LED Dimmable Lightbox
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Build your own 18 watt LED light box 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.
 
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Step 1: Materials

Picture of Materials
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Light Box
  • 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 1 watt resistor
  • 4 x  1N4148 diodes
  • PCB
  • PCB standoffs

Step 2: How many LEDs will I need?

For white light, 10,000 lux is recommended. Lower lux levels may be used but it may take longer. 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. It was modified to allow the dimming of multiple LED strings. For power supply voltages above 15 volts, the gates and 555 timer will need a voltage regulator. The LM7812 may be used.

Step 4: Mount LEDs to Heatsink

Picture of Mount LEDs to Heatsink
Mount the LEDs with epoxy.

Step 5: Cut Holes in Box

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

Step 6: Cut a Square for the Cover

Picture of Cut a Square for the Cover

Step 8: Sand the Inner Surface of the Box

Step 9: Wash Metal Box

Wash box with soap and water to remove metal shavings.

Step 11: Enjoy the "Sunshine"

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famosas9 months ago
hi. im new to electronic. i want to ask this. how about the maximum effiency of your driver? thanks
hanlin_y (author)  famosas9 months ago
Around 90% efficient in this circuit.
famosas hanlin_y9 months ago
then if i use a higher voltage supply i use buck converter so the efficiency will decrease more right?
what is the rating for your adapter?
thanks
hanlin_y (author)  famosas9 months ago
You can add more LEDs so their forward voltages add up closer to the power supply's. I used a 2A 12V adapter.