10 May 2015

PowerBook G4 ambient light

The Apple PowerBook G4 was a powerful laptop ... in year ~2002. I was given a non-working 12" unit in case I could salvage some parts for my projects. Well, besides the battery pack that still holds the charge and lots of small screws, not much in there can be reused. But I was intrigued to find out how the typical Apple cover pulsing light works. So I started carefully dismantling the laptop until I was left with the metallic cover only.
While I have not really understood where the pulsing light is, I had a bright idea: use the metallic cover as heatsink for 1W LEDs and create a diffused light lamp.

After four LEDs and a little wiring the object finally shone:

The lamp held at about 10cm from the wall
In the beginning I connected the 4 LEDs in series, requiring about 12V 300 mA, but that voltage was a problem for a battery powered object that had to keep the low and sleek profile of the original source. So I rewired LEDs in parallel, and now I can use a 3.7 V LiPo cell that can sustain 1.5 A of current. That's much easier to recharge and doesn't need a booster circuit either.

The lamp with other room illumination.

Battery and (mesy) wiring.

I am really satisfied with the result. In a dark 20 sq.m room the lamp produces enough light for reading. I need to find a simple way to hang it 10 cm or so from the wall and a convenient power switch (now it is a jumper, the blue one in the third picture).

Possible improvements: PWM the current so that intensity and current drain can be reduced; use a microcontroller to control each LED and put up a light show, ...