I have been exploring and researching different sun-light positioning systems and tracking solutions that use light sensors for the solar tracker design and my main project. Many existing designs seem to utilize LEDs or LDRs for the sensor part of the tracking system, two of these for single axis or four or more for dual axis versions. I would also like to try and understand a bit more about the photo-transistor and photo-diode in comparison to the older photo-resistor or a plain LED as the light sensors for my main project. The differences between these components could be tested with some simple breadboarding, it would be possible to compare signal sensitivity and response with an oscilloscope. It would be appropriate if I work toward developing my own control circuit board to receive the signal from the sensors and drive two external actuators or motors based on the light levels in the next few weeks. I am also interested in testing out a secondary fine tracking system which would use a camera to track the motion of the sunlight, using coded image conditioning and quadrant positioning values to give coordinates and fix a blanced position to the suns barrycenter.
However, to begin with something more simple, as a start point for me as a beginner to get a better understanding about connecting sensors to read and capture data. Then about sending and recieving these signals - processing the data and visualising the output from the sensor. Therefore, for the purposes of this weeks assignment I will first be following the example of Niels - hello.light.45. Then I can progress to making a remote light sensor module for my solar tracker project with four or even an eight sensor array. This would then communicate with an IC control board to power the motor or actuator on each axis of the tracker.
The Hello.light.45 board design is relatively simple, it uses the AT-tiny 45 micro-controller, tied with the 6pin Isp programming port, an FTDI power and communication header, a PhotoTransistor with it's resistor, and another pull up resistor and capacitor.
As before I used Eagle to design the circuit board. With such a simple board it was quick and easy process I added components to my schematic from the fab libraries, I used the 16mm clearance in the desing rules for board layout arranged my components on the board, I found a good trace path using the auto-route feature then used a 'ripup' to manually route traces in a slightly more preferable, neater way in a few areas areas, And decided to go round and change the thickness of the traces making them more robust. After an Ok from the final 'drc' check. Then I was ready to export the monochrome image of the circuit and generate my traces and border cut files to output to fabmodules, in order to create the toolpaths for cutting on the Roland Modella mills. This time I used the Modela MDX 20 as it seemed to give me better definition around some of my traces.
Annoyingly on the above board I have forgotten to wire the sck pin to Pb2 connecting to the RX on the FTDI
review Niel's board>So I ammended the traces in the Eagle file, and will try to get the opportunity to re-make this board. I also tried to bridge the connections with a wire in order to try and program the board I had made.
ammended with jumper wire
Annoyingly when trying to send the C and make file to program my board, I was getting correction errors, after checking my connections with the multimeter I still can't see why, Perhaps I need to remake the board after all!
For the final project the solar tracker system, I have also been working on testing and coding LDR's and PhotoTransistors as inputs for light level sensing. These movie files can also be viewed at the end of Output devices week and during the group project week controlling the output to various motors.