Thursday, October 14, 2010

Refrigerator progress

I've spent the last few weeks being a total geek. My refrigerator uses way too mcuch electricity-- 4A @ 12V-- so I needed to build a timer to keep from having it on all the time.

My ultimate goal is to have a microcontroller interface with my SunSaver MPPT controller and read how many amp/hours I have coming in off the panels, and decide whether to run the refrigerator based on that. I have spent months researching how to do it-- MODBUS protocol stacks, serial interfaces, etc.. I now have a solid design and software that will work, and I'm still working on the last bit of electrical design.

But the rains have already started, and the sun is gone. I can't wait for this fancy interface-- I need to stop this cooler from using more electricity than I have available.

So, in the meantime, I hacked together a little Atmel microcontroller and a relay module, and wrote some code to let me choose a duty cycle of 15 minutes per hour, 30 minutes per hour, always on, and off. I'm choosing them manually, via a switch connected to the microcontroller, but it's better than nothnig. With the 15 minute duty cycle, I'm using only 1A per hour. This keeps me from running my batteries down at night. It's been so dark, I have to use the 15 minute cycle even in the daytime too.

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