In my prior posts on this project:
Smart Solar Lighting Project - Initial design ideas
Smart Solar Lighting Project - Detailed design
Smart Solar Lighting Project - Mechanical designs
Smart Solar Lighting Project - Update 10/2/2020
and then recently for the Project14 competition on Control Systems: Smart Solar Lighting Project - LED Intensity Control System I have documented my progress (and sometime lack there of) on my smart solar lighting system. On one of my prior postings (Smart Solar Lighting Project - Update 10/8/2020 ), three-phase , wondered if a reflector would be helpful in spreading the light to the diffuser. Immediately (after slapping myself on the forehead in a Duh! moment) I wondered, "why didn't I think of that?". Way back in January 2019, while working on my kitchen lighting system, I twice blogged on maximizing light intensities through the design and use of reflectors (Kitchen Lighting System Phase 2 - Part 2 and Kitchen Lighting System Phase 2 - part 3 - Let there be (better) light! ), but somehow, this time, my mind did not go down that path.
It did not take be too long to see the light, and I opened up Fusion360 and got to work. In my first design, I attempted to build a stack of reflectors, with through holes matched to the mounting holes in the PCB to mount the reflectors to the PCB. While this might have actually worked, the holes created little divots in the reflector foil as I lined the inside of the reflector. That and a few other measurement issues (like wrong holes sizes and an interference with the battery holder) left me to consider a re-design (or two) to improve the build. Here are images of the first version:
My next attempt included blind holes in the mounting bosses (0.1" diameter, 0.25" depth) and a notch to accommodate the battery holder. Here are some images (design and actual) of the final version of the reflectors:
In the above image, the reflector foil was installed as for individual parallelogram shapes (see notes in the background of the reflector holder - above), held into place with the adhesive backing. The fit was pretty good, but the foil tended to peel and move easily as I inserted and removed the difusser panels. Laying out my individual parallelograms together, I was able to attached them with tape into a single piece. I then used this template to cut out the reflector foils.
With the new reflector foils, I added some glue stick adhesive (in addition to the adhesive backing) to securely glue the foils to forms. To attach the reflectors to the board, I used wooden dowels (handles from heavy duty cotton swabs) to mate the reflector standoffs, through the PCB mounting holes.
At this point I setup up the light with two different diffuser panels. On the top (battery side) I used the Lighting White Acrylic panels and on the bottom I used the Satinice White Acrylic - Clear panels. I then took some light readings and verified that the reflectors gave me a ~25% increase in light intensities for both panel types over the previous levels (open standoff brackets). With the light meter, I was still able to sense hots spots, but the light intensity levels were far more consistent across the whole diffuser panel. From here it was time to test and verify the fit of the fully loaded PCB assemblies into the acrylic tubes.
It was a snug fit, but the assembly was complete. I had worked hard to get a tight fit, with the diffuser panels (and reflector body) making contact with the inner diameter of the acrylic tube (thanks two my caliper and some long unused geometry). The whole assembly was very tight with no visible movement of the light within the tubing while given a rather vigorous shaking. Now it was time to try everything out, with the sun down.
The first two images are of the Lighting White Acrylic diffusers (first with intensity biased to the center of the image and second off to side). The next two images are of the Satinice White Acrylic - Clear diffusers (with the same intensity biases). So far, I think I still prefer the Satinice White Acrylic - Clear diffuser based on the higher light intensities. These images were taken of the exterior light boxes and decorative glass panels, with no back panels and with be holding the lighting fixtures in place. I am sure that I might be adding some reflected lighting from the rear facing LEDs, as my hand shows in the pictures, so it is still not completely like the final assembly. Either way, I am very happy with the difference that the reflectors have made in the overall lighting effects.
Look back on my task list from my 10/2/2020 update:
I still have some more software to write (and debug), but I am getting close to having a working system. Here are a few things that I need to finish up:
1) complete coding for remote command to the lighting modules (get/set time of day, get/set scheduling information, etc.).
2) complete coding of charging and 'lights on' status messages.
3) rework LED current limit resistors to increase current ( I might also need to change my control MOSFET to reduce Ron).
4) code closed loop PWM function to normalize LED current over the range of battery voltage (I am thinking of a simple PID loop to adjust PWM to achieve desired LED current).
5) finish 3D printed parts for the LED light spacers and diffusser holders.
6) install and commission the complete system.
7) rewrite analog measurement code, switching to 10 bit ADC mode and removing/revising scaling (new)
Thanks for reading along....
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