fan speed control (PWM) fried
So Friday I accidentally hooked up the fan the wrong way and (as I found out afterwards) killed the fan PWM circuitry.
Turned out the fan speed control died "short". This also caused a power surge towards the micro-controller which also died. Strangely it still somewhat worked but when I tried to re-program that always failed. So I replaced the micro-controller for the second time, installed the boot-loader and firmware, and back to business.
Not so fast though, I first need to install a new fan.
So I open the lamp only to find out...
LED brokenI guess my crude mounting with the aluminium brackets put to much strain on the LED die and that combined with heat caused it to crack. Luckily I had a spare lying around.
It's not all bad though, while having the lamp open, I decided to improve some things.
Better LED mounting
With the help of some thick aluminium foil cut to the right size and bolted down, I get a much nicer mounting of the LED. While at it I also improved the location of the thermo-couple. It now sits all the way on top of the LED, right at the official temperature measurement point!
Speaking about temperature...
In my early testing with the LED, I found that when driving the LED at near or full blast (800mA-1000mA) the LED got warm really fast, easily reaching 60-70 degrees Celsius.
With my testing with the whole setup, temperature stayed nice and low, peaking at about 42 degrees Celsius. What is happening there?
First thing I did was measure with the thermo-couple of my multi-meter. Exactly the same temperature. Then I measured the current provided to the LED.
Turns out exactly 330mA is provided when PWM is fully on. And I'm using 3.3V PWM... That can't be a coincidence.
The LED driver officially works on 10V PWM, but I assumed as it was dimming fine with 3.3V PWM that it also supports that. My guess is now they're just using an analog filter to convert the PWM signal to a voltage., and then interpret the Voltage on a scale from 0 to 10V.
Easily fixed though, I created a simple amplifier circuit like this:
Brief testing showed this works just fine! Brief testing also immediately showed the temperature rising again rapidly!
While inside the lamp anyway, I decided to install another heat-sink:
Some more testing showed that even though the heat-sink does the job, some active (fan) cooling is still highly appropriate.
Here the new fan is spinning nicely during a test.
While working on the inside anyway, I got annoyed by all the cables easily blocking the fan, etc.. so I re-arranged and fixed them.
That's where the lamp is at now!