Final project - first lamp assembled
Some progress: I have completed physical assembly of the first lamp, and learned a lot in the process.
The lamp is shown below, with the LEDs lit in red, yellow, green and white.
Read past the link for more thoughts and observations.
Based on experience with the midterm project, I ran a power and ground "bus" the vertical length of the lamp, for the sensors and the LEDs to tap into. This will make things a lot simpler when actually wiring.
However - this means you have to be careful when making some of the cable joints (twisting wires together and soldering), since the LED pins are quite close together, and short easily. This is turning out to be a major problem for me, and manifests as sudden, erratic flickering of the LEDs.
I have also found that the extra resistance of the wires (and possibly the crappy solder splices) changes the behavior of the AD5206 digipot. The LEDs are dimmer, and respond differently to variable voltage. There seems to be a big "step" in their response curve, after which they become much dimmer suddenly.
I have also noticed that when there is a short in any of the LEDs, the behavior of the of the other leads connected to the digipots becomes quite strange.
Todd pointed out that since I am using the 50k ohm part, this is to be expected. At full brightness, it will perform like the 10k ohm part, but at half brightness, the greatly increased resistance will make them much dimmer. I will have to compensate in software for this, and but will end up with fewer usable brightness values.