Thursday, July 19, 2012

Good Day Sunshine On My Arduino

Here's an update on my article Sunshine On My Arduino Makes Me Happy. This is part of my Amigo project, which in part experiments with alternative power sources for eight-bit AVR microcontrollers.

I went from a 1.5W to a larger 5W solar panel, then to much larger 15W solar panel. We'll see if that's enough to charge the 12V battery during the day and let the system run all night. I also had to go to Xbee Series 2 radios with external antennas on both the Arduino Uno with the Xbee shield in the "instrument pod", and on the Xbee Explorer that is USB connected to my desktop, in order to get the range I needed. The chip antennas couldn't cover the few tens of yards from the south-western edge of my back yard through a wall to my home office on the south side of my house.

Here's the instrument pod with its external antenna visible at the lower left. The pod looks fluorescent green in the photograph. It was originally a translucent white that I spray painted fluorescent yellow. The pod looks a lot better in the photograph than it does in real-life; it definitely has a cobbled-together look about it.

Instrument Pod: Cover Off

Crammed into this little box is the Arduino Uno with the Xbee shield, a battery meter activated by a tiny pushbutton switch, the solar charge controller, and a 12V sealed battery. The software on the Arduino merely pings my desktop every second. (In the past I've written about various environmental sensors I've already tried on this platform.)

Here is the instrument pod at the edge of my back yard connected to the largish (about 42" x 15" or 105cm x 38cm) 15W solar panel.

Instrument Pod and 15W Solar Panel

Here is the tiny Xbee Explorer, dwarfed by its own external antenna, USB attached to my desktop Mac.

Xbee Coordinator on Xbee Explorer

I'll monitor this for the next few days and see what happens.

Update (2012-07-23)

The instrument pod has been up continuously for over four days now. It pings my desktop once a second. The state of charge meter I have hooked up to the 12V battery, activated by a little pushbutton inside the pod, shows the battery to be completely charged. So far so good.

Update (2012-07-28)

The solar-recharged instrument pod has been continuously wirelessly pinging my desktop via its Zigbee radio for just short of nine days now, having survived several rain storms. Here's a snippet from the log file below. The ISO 8601-style time stamp is generated by the logging script on my desktop Mac; the duration timestamp, showing eight days and twenty-three hours, is generated by the remote Arduino in the instrument pod, and indicates how long the Arduino has been running since it last powered up.

2012-07-28T10:00:03 8:23:36:30
2012-07-28T10:00:04 8:23:36:31
2012-07-28T10:00:05 8:23:36:32
2012-07-28T10:00:06 8:23:36:33
2012-07-28T10:00:07 8:23:36:34
2012-07-28T10:00:08 8:23:36:35 

Update (2012-08-09)

The instrument pod finally lost power after running continuously for more than ten days. I could tell by periodically checking the battery's state of charge that the solar panel wasn't keeping up during the day with the loss of charge during the night. But while I would have preferred it stay up, this gives me some hope that by just mounting the solar panel in a better, more sunny, location, it might work continuously during the summer. Whether it do so during the winter is another matter.


Hari said...

hey, nice equipment u have got there. Great idea. I am actually working on a solar charge controller. So it would be nice if u could supply me with the source code and circuit and help me in my project..

Thanks and regards

Chip Overclock said...

I'm afraid there's not much more to report! I'm mostly a SW guy, so all the solar stuff was off the shelf parts which I cite in the original article "Sunshine On My Arduino Makes Me Happy".

The FW on the Arduino was a simple "print a line every second" just to send a heartbeat via Zigbee to my desktop so that I could tell when the system ran out of power. I haven't been able to wrap that project up due to other work, but eventually hope to mount the big solar panel up higher at an optimal angle and direction to keep the battery charged up and the board running. But so far, it dies after a few days. Still, I'm optimistic.

Best of luck!