Solar Powered Arduino Project

Hello Arduino Community,
I am building an Arduino project that will need to be solar powered. The project will draw about 500 mA and will need the standard Arduino input voltage (9-12 volts). I am looking at using this panel or something similar and probably some kind of a voltage regulator. I would prefer not to use a battery; when there is enough light, then the project will run.
The part of the project that I am concerned about is when the solar panel is not supplying ample power (<9 volts or 500 mA) to the Arduino. Will this cause any bad effects or harm anything? Also, what would be the best way to regulate the solar panel voltage? Any other solar power tips?
Thanks for the help,
icecats

The part of the project that I am concerned about is when the solar panel is not supplying ample power (<9 volts or 500 mA) to the Arduino. Will this cause any bad effects or harm anything?

Possibly. It depends on the project. The Arduino certainly does not need 9 Volts or 500 mA, so what does?

The Arduino itself and alone needs about 50mA to maintain it’s internal 5V regulated voltage. When the voltage/current won’t be sufficient to maintain the internal voltage the Arduino will become unstable, unpredictable and then shut down ?!? I can’t say if you’ll damage the Arduino or not but I guess it cannot be worse than unplugging the Arduino from my computer. The small capacitors are discharging quickly in that case I agree and the unstable time is shorter. I refer you to this graph.

It is possible to find on the web some easy transistors/Zener or OpAmp circuits to sense the voltage and trigger the power on/off quickly at a fixed voltage if you want…

For the voltage regulator (current < 1A, solar panel Voltage <28V open-circuit) using a LM7812, LM7809 or a LM317 is a easy common practice. You can also consider to buy a dc to dc converter…

I think this is fairly complex.

One thing to consider is that as the sunlight increases in the morning the MCU will initially be starved for power. During which it will power up and shut down many times. When the supply voltage does such things it can trigger CMOS latch-up.

And the latch-up may not clear if power is not sufficiently removed.

darn, post got lost again from this site bumping if someone else posts while you are writing.

forget the array of multiple voltage regulators.
eliminate the arduino voltage regulator, it sucks power.remove it from your board.
power the arduino with your 5.0 volt supply not a 9 volt.

put your arduino to sleep and wake up, run the sketch, then sleep.
you can easily get 1/10 the power use

also, if you have sized your batteries for 5 days storage, to allow for a storm and no sun for 5 days, then there is no need to power your duino from the cell directly. that just adds complexity without benefit.

clarification ???????????????????????????

You did not state that you wanted to ONLY run while the sun / PV cells are delivering over 500ma and the rest of the time, nights, rain, snow, the unit will have no power and not run.

you ask what would happen. readings will get wild while the unit is failing do to loss of power.
relays will fail to their un-powered state, possibly dither as it fails.
just check power and at some low threshold, freeze the program.