Del Mar Fair Exhibit & Largest Solar Fountain yet!

Hi There,

Too long without a post. Been busy with many experiments, projects, two river trips (canoe/camping and Kern whitewater), life, and get-paid-for-type-work projects.

The controller is running pretty good. Needs some software reworking but hardware is solid so far. The motor controller that worked fine at Earth Day with the 1 amp pump got pretty hot with the 9 amps being pulled by the three 1200 GPH pumps I put in my newest, and largest backyard solar fountain yet. Check out the pics below.

I started this project but paid some pro's to finish it. I have plenty of 3" PVC from my failed experiments if anyone in N. County has a drainage problem :)... let me know I can hook you up!

Anyway I had a MOSFET thermal issue (i.e. overheating to the point of cooking the PC board to a charcoal crispy and delaminating the TO-220 MOSFET package, rainbow tempering the leads... Good stuff. The guys at All About Circuits forums helped me out and I have it fixed now simply by lowering the value of the series resistor between the GPIO pin on the PIC and the MOSFET gate. From 1.9K to 100 ohm. It's all in the new schematic which I'll post as soon as I add some circuit protection (actually burned a trace off hooking up the battery wrong the morning of the day before Earth Day... one more green wire). I'm on the fence as to whether or not to use a further optimization that the power guys like, the gate driver for the MOSFET. I'll have to test and figure out how much performance improvement the gate driver could provide and see if it's worth the money to add it and the various discreets to the board to support it.

Here's the deal on the FET gates. You want them to be either on or off. The in between stage is where the resistance happens and your pushing all your amps through that resistance and generating heat. A small problem, when repeated 5,000 times per second, becomes out of control (in the form of too much heat) fast. So the gate driver sends all kind of current fast to the FET gate and snaps it on and off cleanly. Thus wasting less energy to heat (which is good and efficient) but I'm not sure that it would pay for itself during operation over a year or two. Right now with the 100 ohm it generates no heat, at 12 volts and 9 amps that I can sense with my finger so that's not much efficiency burning off. It deserves a proper experiment with good measurements and math to make a decision though.

Come on down to the Del Mar Fair and check out my fountain. It will be installed as part of the Green Acres Nursery exhibit. http://www.greenacresvista.com/

So check it out and let me know what you think.