Targeting Subsystem: General Purpose Microcontroller for Intelligent Solar Tracking 

April 2005

Spring already in Michigan's Upper Peninsula. Now this is really odd! We've been up here for over ten years straight, and on/off for over two decades, and we have never seen spring time this early. I don't know about the rest of you, but I've tracked the progression of global warming for a number of years, and the fact is -- it's here. 

About the only idiots still clinging to the "ain't happening" dogma are Bush, Cheney and a small group of republicans and industry-paid "engineers". Even knuckleheads can see that the earth is warming steadily as combustion and pollution increase, which makes somebody like Bush "dumber" than a moron. (Isn't political free speech fun? Let's use it before it's gone -- you never know how homeland security will be twisted around now that Gonzales is in.)

Along with global temperatures rising we see the ozone layers around the North and South poles diminishing. The northern ozone hole extends down as far as northern USA, which is why the sun here in the U. P. is brighter and whiter than normal -- with less filtering of ultra-violet rays. 

That creates a situation that is both positive and negative for those who live here. It is positive in that solar energy is more abundant, but negative in terms of health. UV rays are extremely hazardous for your eyes and skin. Advisories in our local area call for everyone here to wear sunglasses at all times of the year on sunny days.

So it looks like solar heat is going to be a good source of free energy for the duration. I'm all for it, as I'm sure neither you nor I will be able to keep up with the soaring costs of fuel. If China and India want to pay the skyrocketing costs of imported oil, let them have it -- we can do much better on alternative energy. Now if we can't get the Republicans to get their heads out of the sand and move the country from fossil to free energy, too bad. What the country puts up with, they'll have to answer for. But in my company and our turbine builder's club, we are moving on into the future!

This month, as promised, we are going to begin looking at aiming/tracking systems for our solar reflector. 

In a lot of these designs discrete components are used -- op amps, transistors, resistors, capacitors, etc.

The design I am presenting uses a microprocessor -- in this case a PIC 16F84 which allows us much greater freedom of movement in four directions, and opens the door to intelligent robotics.

PIC 16F84

The PIC 18F84 is both low cost ($5-$10 each @ Digikey) and easy to use with low-cost development tools. The versatility of the processor is what I first look at when choosing a microprocessor. The 16F84 part is probably the most universally versatile chip I've worked with so far. Even though the chip has only 18 pins, there are two input/output ports -- one with 5 bits and another with 8 bits -- for a total of 13 general purpose pins. (See Figure 1)

Figure 1 - PicBasic Compiler circuit

You will also notice from the above diagram that this chip requires very few discrete parts in order to function. In this example, the cpu may be programmed to blink the LED on/off to show it is "alive". Using MELabs' PicBasic Pro makes it really easy to assign particular functions to individual I/O pins.

For example, RB2 and RB3 may be allocated to communicate with a PC-compatible through its serial port. RB4-RB7 may be assigned sensor input tasks, with RB0 and RB1 driving LED's for visual feedback. Finally, RA1-RA4 may signal relays for energizing tracking motors, with RA0 sensing a clock alarm input.

So there you have a good idea of how to configure an easy to use, general purpose, microcontroller for intelligent solar tracking.

If all of this looks daunting, don't worry about it -- for those of you who are not suited to developing microprocessor systems, we will make available a pre-programmed microcontroller board at the end of this series.

Next month we are going to continue with our discussion on the microprocessor system. We'll take a look at how to connect cadmium sulfide and phototransistor light sensors to the cpu, and how to write a simple program to test the sensors and report to a host system.

We will also take a look at a new 4.5-inch hot rotor kit we are planning to offer to our club members in the near future. We have just recently sent in a work order to our laser cutter for about 50 units, and we should hear back from him shortly.

Until then, keep working on your project and let us know how you're doing on it.