Mother's Solar Tracking System

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HOW IT WORKS

OK, so now you know what this solar tracking rig is supposed to do ... but exactly how does it do it? Well, to begin, the movement of the frame (which, by the way, is counterbalanced—below its pivot point—to offset the weight of the boiler out on the 10-foot pipes) on its vertical axis is accomplished by a length of nylon line fastened to each of the frame sides. And this rope, in turn, is threaded around a regular 6-inch V-pulley which is connected by chain drive to a readily available Chevrolet electric window motor.

When (every three minutes or so) the motor is temporarily activated by a phototransistor in the electronic tracking system, it rotates the V-pulley slightly ... which pulls in a bit of the rope and causes the frame to move a tad. Thus, in effect, the frame "tracks" the sun across the sky.

Of course, this movement could go on indefinitely ... if it weren't for two very important factors: [1] The same phototransistor that turns the motor on also turns it off almost immediately (by virtue of an ingenious housing that casts a shadow on the sensor when the mirror frame moves slightly), and [2] towards the end of the day, when the sun is too low in the sky to be effective, a small "arm" mounted at one pivot point of the tracking frame kicks a switch that reverses the motor and brings the entire frame and boiler assembly back to its original position, ready for the start of a new day. (When the frame returns to its starting point, another switch is triggered by a second "arm" to stop this reverse flow of current in the motor ... which effectively shuts the motor down and sets the system back to "normal" so that the sun's rays can repeat the cycle.)

SHOPPING FOR PARTS

To make your parts shopping as uncomplicated as possible, all the electronic components for this project have been taken right from Radio Shack's 1979 catalog. If you can't locate a Radio Shack retail store in your area (there are over 5700 stores and dealers nationwide), write to Radio Shack, 500 One Tandy Center, Fort Worth, Texas 76102 for further information.

For the most part, all of the mechanical parts used in the tracking system are common items that you'd find in any shop, garage, or junk pile. Although we found that the Chevrolet (Delco) electric window motor used to drive the system is entirely compatible with the existing electronics, there's no reason why—if you're experienced in electrics—you couldn't use just about any window or windshield wiper motor to accomplish the same thing. In short, with a little bit of Yankee ingenuity, most any drive motor will work with this system.

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