UPDATED 6/25: Jerald Cogswell has created a gadget designed to find the sun for solar applications. He put light sensors in baffles, and his device takes 30 samples vertically and 30 samples horizontally to determine the brightest intersection. The process identifies the optimal spot to point solar collectors.
Using the same multiplexing gadget, Cogswell can find the inventory for each item in a vending machine, find and sort the heaviest macadamia nuts on a factory line, or sense the position of a magnetic or inductive source.
Jerald Cogswell's sun finder multiplexes 64 light samples to one microcontroller pin.
This multiplexing project can be modified by adding output routines to the program to drive motors or other devices.
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I remembered Forrest Mims describing his solar tracking device in the defunct Science Probe Magazine. It consisted of an analog circuit driving a dc motor. The detectors for the circuit were solar cells attached to the dc motor. Based on the sun's position, the motor will point the solar cells in the direction of the sunlight. As explained and demonstrated in this project, a small microcontroller can enhance the performance of such a basic sun tracking device. Cool project!!
Here in Europe, I would choose a microcontroller with a built-in RTC (real-time-clock). Knowing time and date, I can predict when the sun appears on the horizon, the elevation and when it disappears again in the evening. On cloudy, rainy days it might be useful not to switch on the servos. However, if the sun shows some erratic behavior which makes it necessary to follow it by an X/Y-tracker, your circuit might be better... (but I've never seen this on our planet).
I have my old design for sure. All this interference and "chatter" can be eliminated by integration and delay of a signal that is usually splendidly done by installing a capacitor in the output driving circuit.
I mostly agree with you. In fact, I tried connecting four photocells to four opamp comparators. I ran the non-inverting of one into the inverting of the next one in a ring. The binary search for right/left, up/down didn't work. It kept getting distracted by clouds and rocks and shadows and the motors went wild like a hound dog on a scent. If anyone has an efficient analog design, I'm interested.
But, again, I'm disappointed that everyone focuses on the solar application -- but then I guess I should have changed the title. The circuit and program is really about multiplexing in general. When I did aircraft flutter tests back in 1980 this little circuit would have been more powerful than the DEC PDP 11/70 we were using.
I tried to understand "almighty" processors being used everywhere. From MP3 players to refrigerators and even coffee machines.Why do we love to complicate things? I agree with John E , who described a design similar to the one , that I published (with Bob Pease blessing) about 30 years ago in Popular Electronics. Hundreds of trackers are using it and it has only 4 photo resistors and simple differential-servo system.I had tons of positive feedbacks and never heard anything negative on it , except that some people did not understand how servo works and what kind of transistors to use on an output.Sixty phototransistors?Isn't it a bit of overshoot?It would be great for navigation , but to move solar panels we do not need such a sophistication.Just my humble opinion.....I always loved analog.
Rob, thanks. I had gone through the source code and trying for an implementation. I will let you know within a couple of days that, whether it's working fine or not.
Andrew Morris designed a circuit that could detect a stroke victim's groan and convert the sound into a signal so caregivers would know when help was needed.
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