measuring effective solar areas

I'm working on a small robotics project and one of the things I've been trying to consider on self monitoring is how to measure how effective the solar is at any given moment as well as what areas are better for solar. In effect, if the robot is autonomously roaming the house, did it get more light in position X or position Y? I haven't programmed it yet to be smart enough to charge itself when the batteries are dying, but thats where this is eventually going to lead, just baby steps for now.

My problem is, I'm a programmer who's fell in love with arduino but still really learning the hardware side. Someone recommended measuring my solar panel output which sounded great, and I saw a thread here that looked similar to what I wanted to do. My only problem is, I don't know how to figure out what resistors I'd need.

Here's my setup, my arduino is being powered over USB, which comes from a 12v battery/solar controller/solar panel.

The solar panel is a 12v 5.2w panel.

For all practical purposes for my project, the number can be almost anything, as long as sunlight makes a higher number and darkness makes a lower number. I just want to make sure I don't fry my board!!

I really appreciate any help that anyone can send my way.

Unless you can get to a location with direct sunlight, there won't be enough light indoors to make a significant difference in battery life for a robot.

You can easily estimate light intensity with an LDR and a resistor, connected to an analog input. Google "arduino light intensity" for thousands of examples.

Or, just walk around and measure the [u]current[/u] output of the solar panel, using your multimeter. That experiment will show you what I mean about charging a battery.

The robot is being setup for off the grid operation, I didn't want something confined to my living room, lol. I've set it up so far to operate in a manual mode where I've got a pi and xbox controller receiver to treat it like an RC car. When I toggle it to auto mode, it'll pick a speed and get up to that speed (it's a quick attempt at keeping the movements from being jerky), that works with a couple ultra sonic distance sensors for obstacle avoidance and drop offs like stairs inside or cliffs I suppose outside.

Like I said, right now I'm just collecting data, and LDRs look like a definite option, but if I can just use the panels almost directly then that makes more sense to me. The reason I'd measure sunlight is for the panels, so if I can get their readings then that seems like my most accurate approach.

If that was my project I would arrange the connections etc for my solar panels to capture the maximum energy from the available light and I would use an LDR to measure the light. LDRs are cheap and simple to use compared with trying to measure the output from a solar panel.

...R

2 responses and both say to use LDRs, I think that's what I'll do then.

What voltage is your battery? can the battery/load be less than 12 volts? If so I would look at whether an MPPT solution is worth considering, remembering that Solar energy is different to light levels. To get an idea have a look at solar pressure for your area compared to the number of hours of daylight, as an example I live in Auckland NZ, in the winter we get a total (cumulative) 2.43kwh/m2 from about 9 hour hours of daylight.

you could always put in panels outside to charge batteries then have a simple docking station inside

simple docking station