I thought I would give you some pictures of my project. Its up and working now.
I built a plant nursery irrigation system. Basically the system uses 64 bit unsigned integers to schedule device turn on and turn off. The system uses a priority queue (a min heap) to accomplish the scheduling. I am using one of the at90usb646 timers set up for .1 ms interrupts to keep the time of day. The system works well.
This is how I started out
A 555 drove a couple of counters, which triggered a 555 configured as a one-shot.
This is the teensy++ version that does the exact same thing except its accurate, expandable, and only has two devices on the board other than teensy++. You may wonder where the heavy wire is that goes to the pump. At this stage of development, I was turning on LED's that were illuminating two on at dusk off at dawn devices that in turn were switching the AC to the pumps. You can get the gadget at home depot. It worked well for development, but it does exactly what you don't want it to do if the device loses power. If you're driving pumps, that means trouble.
Here's the final board. I say final, but I still want to add a real time clock to it at the very least.
The only thing that deserves much comment is that I solved the problem with usb power fighting with external power by modifying the USB cable. I stripped it back and cut the red wire - no more usb power. The system works great and it can communicate with my computer.
Here is a system picture.
You can see, I'm using lamps as test devices.
Finally here is how it looks buttoned up.
The reason that my herb garden looks a little mangy is that I made shish-kabob and basil bread last weekend. Mr. Herb Garden has yet to recover.
Thanks for all your help. I can't wait for teensy++ 2.0.
Keep up the great work!