Solar powered Arduino

Hi all,

I'm working on a project to run an Arduino off of solar power. Well actually I'm charging batteries every day, and running the Arduino at night. I'm using a flexible solar cell that generates 7.2 volts, instead of the normal silicon cells that generate .5 volts per square, so its pretty convenient to drive an Arduino directly with during the day. I had one that was rated for 100mA and it could keep the Arduino alive even in the shade...

There doesn't seem to be much on solar in these forums so I thought I would post, even though the project is not complete. Here is more info, including schematics:

http://effluviaofascatteredmind.blogspot.com/2009_09_01_archive.html

Looks like you have been having fun . When the voltage can change as it does down round the levels you are working at ,any calibrations of devices read by the arduino can be out ,by 10 degrees C in my case. The arduino (atmega328 in my setup) needs the voltage to be over about 7.4V it seems to hold steady voltage in.

I have a 12V SLA 7AH battery attached to a small solar panel .It drives a couple of 1 watt LED lamps at night . Hooked up the arduino and it runs fine. Monitoring a freezer . Only had it running for about 2 hours and had to rework something else on the freezer controller so turned it all off .

Didn't see any reason for it not to work for long periods. Arduino is consuming about 40mA as I have it set up . The voltage regulator was holding steady at about 4.93V and that should continue down to about 7.4V out from the battery and I wont let it get down there.

I am working towards radio modules on the freezer end and on the computer next. I like the LEDs under the table though ,might put some in my setup which will also light and run a fish pond at night. Thats another story

Yea lots of fun!

I'm plugging the batteries DIRECTLY into the 5 volt line that powers the Arduino. That is, I'm skipping the regulator. This works because the batteries are essentially "regulated-enough" power supplies, and in fact pull the voltage generated by the solar cells down (the Arduino is off when the cells are "on" anyway).

I think that you are right. If I wanted to plug into the Arduino's "Vin" (i.e. go through the regulator) I would have to have another battery to bring the voltage up higher. For some apps, that might be a small price to pay for over-voltage protection, but for my app it should be ok to plug direct & it is more efficient.

But when I was experimenting with running the Arduino directly off the solar cells (instead of charging the batteries and running it at night), I did plug the cells into the Vin (because the cells generate 7.5 volts) and it worked in both sunlight and shade.

Yes 40ma is basically what I got too.

You project sounds pretty interesting. Since you were driving a few 1 watt LEDs all night it sounds like you are pulling and storing a lot more power than I am planning on.

That's an awesome solar powered coffee table thing you got going on - great stuff!

Solar Generator, Is it environmental friendly equipment? Ideal for camping or emergency power outages, the Sun Power Port is a portable generator that when used to its full potential will pay for itself in less than two years. In one day of full sunshine, the solar panel easily charges the 12 volt (standard automobile) battery. An inverter changes the DC current to AC. http://www.sunpowerport.com