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Gadget Freak Case #217: Finding the Sun With a Microcontroller
6/22/2012

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This multiplexing project can be modified by adding output routines to the program to drive motors or other devices.
This multiplexing project can be modified by adding output routines
to the program to drive motors or other devices.

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radioman63
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Re: Bob Pease must be rolling in his grave.
radioman63   8/27/2012 11:04:50 AM
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Yes!  I remember reading that article 30 years ago.  Would you be able to point me towards a copy of it?  Thanks.

mrdon
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Gold
Re: Any Analog Solutions?
mrdon   7/22/2012 9:34:50 PM
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The motors were probably driven by discrete or IC based H-Bridge circuits. These circuits are commonly used to provide directional control for motors.

mrdon
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Re: Bob Pease must be rolling in his grave.
mrdon   7/22/2012 9:22:00 PM
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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!!

charly5139
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Re: Bob Pease must be rolling in his grave.
charly5139   7/22/2012 5:04:59 PM
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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).

Regards

Charly

Chris PE
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Re: Bob Pease must be rolling in his grave.
Chris PE   7/5/2012 1:06:56 PM
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@Jerald,

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.

Best Regards,

Chris

78RPM
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Re: Bob Pease must be rolling in his grave.
78RPM   7/4/2012 6:45:39 PM
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Hi, Chris,

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.

Jerald Cogswell

Rob Spiegel
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Blogger
Re: A question of efficiency
Rob Spiegel   7/3/2012 12:54:34 PM
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Thanks, Mydesign. We are certainly eager to see the gadget. 

Cadman-LT
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Platinum
Re: Bob Pease must be rolling in his grave.
Cadman-LT   7/3/2012 11:31:06 AM
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I thought that this had to have already been done..for the solar. As it turns out I was right.

Chris PE
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Bob Pease must be rolling in his grave.
Chris PE   7/3/2012 11:21:37 AM
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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.

Mydesign
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Re: A question of efficiency
Mydesign   7/3/2012 4:55:58 AM
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1 saves
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.

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