[Part 10] Electrical Design - Adaptive Headlights Assembly




The adaptive headlight design is simple. The intensity of headlights are quantized into four steps by means of applying PWMs at four different duty cycles. In order to do this, I’m using a fast LED drive from Luxeon which, for its fast and precise reaction time, can even be used for strobing application according to the company website. The Propeller chip reads ambient light condition from the light sensor and depending on the reading, it outputs PWM at preprogrammed duty cycles. If it’s all sunny and bright outside, the headlights turn off itself without a user input. If it gets darker, the intensity gradually increases, again, without a user input.


The headlights were also custom assembled. The fact that the actual LED element is so small makes the soldering job particularly difficult just as it was very hard to solder resistors on the OSMC board. The LED mounting base from Luxeon is a solid aluminum plate. Therefore 30W soldering iron was not powerful enough to do the job. 


Instead I used my electric range to heat up the entire LED mounting board and then dropped the same size soldering bits on it to do the job. This is again, non-standard soldering, but it works perfectly fine. I just had to make sure I don’t drop at a wrong spot.


This is a power line for the mounted LED. It’s just 2 channels stripped off from my ribbon wires.


Each LED is so strong that it needs a cooling fin otherwise it will burn out after a period of time. I made my own headlight housing out of the same rectangular stainless steel pipe I used to fabricate the navigation pole. 



Between the fin and LED, I applied thermal paste to boost thermal conductivity.


Everything is tight pressure fit. Not a single screw is used to hold the geometry together. The fin was fixed to the base with epoxy.


This is a finished headlight. You can see a rectilinear array of optical surface. This is an elliptical projection lens. I chose this over the regular parabolic reflector design because I want to light up wider horizontal area and not too much vertical area so I can see the ground terrain better at night while not too much disturbing opposing pedestrians with bright light.

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