I have recently been working towards updating the sun tracking / heliostat electronics documentation. I am planning on adding a few new components along with rearranging some of the old ones. I think I will probably add some switches for manual control of the machines, but we'll see how that goes with the code first.
The pdf below shows what has already been done. So far, everything has been designed in Fritzing, but at some point I want to draw out a proper schematic and hopefully even put together a PCB for an Arduino shield. http://www.cerebralmeltdown.com/wp-content/uploads//2012/06/SunTrackerCircuit_bb.pdf
Sometime in the near future, I am also planning on doing a design for the Arduino Mega since I have managed to get sun calculations with much better accuracy to work on it. Technically, the program would work on a regular Arduino as well, but the program is so large that it doesn't fit.
One thing to note is that the circuit in the above pdf uses the Arduino Duemilanove. The newer Arduino boards, like the Arduino Uno, have extra SDA and SCL pins which the RTC can use in place of analog pins 4 and 5. As far as I know, you can still use analog pins 4 and 5 on the Uno, but then you wouldn't be able to use them for other things.
On a final note, I still need to add electronics for controlling multiple machines. I think I should be able to use triacs in place of the mechanical relays used in the past, but am still waiting for them to arrive in the mail before I can try it out.
If anybody has any ideas for things that could be added or improved, let me know.