Shifting Solutions

The schematic of Figure 2 is one that I developed back in 1978. It is by no means perfect and there are many ways to accomplish the same thing. I am presenting this design as an experimental version that does work. The point here is that a circuit like this is destined for some evolutionary changes, especially if enough people start experimenting with the idea. I have used this exact circuit to drive a windshield wiper motor and a threaded shaft hooked to a piece of plywood. It all worked just fine. Watching a piece of plywood track the sun was real satisfying, even though it sounds rather demented. Actually it really WAS demented, but electronics tends to do that to it’s practitioners. I did not have any P.V. home solar panels back in ‘78 either!!

Parts List
Integrated Circuits
U1 & U2 NE555 Timer, in 8 pin DIP
Transistors
Q1 & Q2 Phototransistors ECG 3031- $10.84, ECG 3032- $11.13, ECG 3034- $1.68
Phototransistors from slotted optocouplers- SDP 8403-301 Radio Shack Infrared phototransistor – $1.98
Q3 – Q8 2N3904 or any small npn 2N2222A, etc
Q9 – Q12 2N5294 or any NPN with Ic > motor current Zeners Z1 & Z2 3V-9V zener Z3 & Z4 18V – 24V zener current rated >1/2 motor current

Of course building a tracker system is a fine start, but now a days, you can actually use it on a home solar power system, instead of the plywood I originally used. To find out how you can build your own solar panels easily and cheaply, click the link above and explore the many options avaialble along with teriffic reading materials availalble on a wide variety of topics in sustainable living, green construction and so much more.

See ya Monday

The right side of the circuit works almost identically as the left.

Close inspection of the right channel circuit reveals that the motor control transistors have been “swapped” in terms of the polarity. This makes the motor run in reverse when needed. The two transistors (Q5 & Q8) provide insurance against short-circuiting the power supply through Q9/Q12 and Q11/Q10 by assuring that only one channel may operate at any time. Q5 disables the right channel when the left channel Q1 is turned on and the reverse scenario happens with Q8 when the left side is energized.

The circuit as it stands is flexible. It will run on supply voltages between 6 Volts and 16 Volts without any modifications or performance degradation. The 2N3904 transistors are not critical. They may be replaced with virtually any small signal switching transistors, like the 2N2222A. The zener diodes could easily be replaced with versions having zener voltage anywhere between 3V to 9V. I used heat sinks on the motor control transistors for reliability. With the present circuit it should not be necessary to bother with heat sinks on Q9-Q12. There is nothing special about the 2N5294 transistors. They were cheap and readily available. I did like the TO-220 case outline since a single 4-40 screw is the only necessary hardware.

Substitutions for Q9-Q12 only need to have collector current maximum ratings that will accommodate the specific motor used. All resistors used can be 1/4 watt dissipation. Add some series resistance to the motor if you want it to operate more slowly. This will allow you to use motors that have high RPM at rated voltage.

You know, the ability to build your own solar panels is really rather quite simple. Click on the link at left and you’ll find several DIY home solar system kits available that show you in clear language and precise drawings with videos the complete process from where to find the cheapest materials locally, how to assemble them, mount the units and connect to the power grid of your building. From those with experience, we know this can be a fun weekend project. But more importantly, having your own renewable energy system will save you hundreds of dollars a year in electrical costs from your utility company. Building your own solar panels systems will also save you thousands from having a company do it it for you. They don’t take long to build, give it a try! Click the link above and exp-lore the possibilities.

The Electronic Works
The photo transistor sensing and motor control circuitry as shown in figure 2 ( see tomorrows blog) has a left and right side which are mirror images of each other. When Q1 is shadowed, it is turned off, and there is no current flow through R1 and R2. The voltage on the zener’s cathode is below the 5.5V threshold necessary for any current to flow through the zener, so Q3 and Q4 remain off. The 555 timer output is low, and Q9 and Q10 are turned off, leaving the motor with no applied voltage. Light shining on Q1 will turn it on, applying 12 Volts across R1 and R2 and the 10k current limit resistor. R1 and R2 are sensitivity adjustments allowing the user to accommodate various photo-transistors. Q3’s threshold is determined by the sum of the zener voltage and two base-emitter diode drops through Q3 and Q4 or Q5 (whichever is greater). When Q4 and Q5 turn on, Q4 will discharge the 4.7μf capacitor connected to pins 2 and 6 of the 555 timer. When pins 2 and 6 of the timer are below 4 Volts (1/3 of the supply voltage) the timer output (pin 3) will go high. Pin 3 will source current into the base resistors of motor driver transistors Q9 and Q10, turning both of them on. The motor will begin to turn, moving the PV panel in the proper direction to shadow Q1 from the sunlight and turn off the motor. The 555 timers were used to generate a pulse extension that would ensure a small amount of mechanical overshoot for the motor so that the system will not draw current during shadow mode. Total idling current is on the order of a few milliamps.

Great, we’re well on our way. Just wanted to remind you that there are DIY kits available that show you how to build your own solar panel systems, and a wind power generator rather cheaply and have a weekends worth of fun while building your own renewable energy system. Click the link above and find several kits worth pursuing, you’ll also find reading material on sustainable living , green construction and solar panel systems as well as residential wind power systems that can make fun projects. Interesting to note that the instructions are so clear that even my wife was able to build one on her own. By that I mean, that she normally is not all that familiar with even the simplest of tools,( though I am sure that some women are just as handy as most men! ) but is great with following precise and clearly written directions and videos.

Tomorrow, we finish up the circuitry, check back

AN ACTIVE SOLAR TRACKING SYSTEM

This is a four part series on building your own home solar tracking systems. I hope you enjoy the article and find it of some value as your pursue the sustainable living lifestyle that cam be fun to achieve.

In the spirit of fine home-brewing, this tracker uses cheap ubiquitous parts – a windshield wiper motor and a 555 circuit – as the guts for an efficient machine which keeps panels aimed at the sun.
How This Tracker Works:
Driving a threaded shaft attached to the tracker’s underside, the windshield wiper motor is powered by a circuit controlled by two photo transistors which are turned on and off by a shading device.
The photo transistors and shading device are mounted on the face of the tracker and the tracker rotates in the appropriate direction so that the shading device blocks sunlight to both photo transistors.
State B in Figure 1 shows the tracker facing the sun so that both photo transistors are in shade. As the sun progresses across the sky the right hand photo transistor is turned on (state C) and the tracker moves (clockwise in Figure 1) until both photo transistors are in the shade (state B). This CBCBC…BCB pattern ends at night in state B. In the morning the tracker is in state A (it is in the same position, but the sun is on the other side!) and the motor turns on swinging the panels from their night time position until they face the sun.

Tomorrow we’ll discuss the electronic components that make up this incredible little cost effective device.

But as you sit around pondering the feasibility of building one of these your self, you should also, consider the aspect of how to build your own building solar panels to use the tracker on. they are incredibly easy to build yourself, even for the faint of heart. It can make for a fun filled weekend, you might learn a thing or two as you go along and even though you can build a solar panel system all by yourself, you can invite your buddies over for beer and have them help you…it’s amazing what friends might do for a free beer!

Click the link above and learn how you can save a ton of money building your own solar power systems.

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