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I'm working on a solar powered project. I need to measure voltage on the battery and voltage coming from the solar panels.

I made two simple voltage dividers and they work great on either Battery or Solar Panel, but it gets real funny when I try to measure both at the same time. I think it has to do with a common ground. Has anyone managed to do this? Any ideas?

Thanks
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Hi bikemind

You'll have to be a bit more specific than ...

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but it gets real funny when I try to measure both at the same time.
smiley

But, at a guess, do the readings get better if you analogRead() one device twice and use the second of the two readings, and then do the same for the other device?

All the best

Ray

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If this is a hardware question , what is the chance a schematic would help ?
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If you can, measure them at least 100ms apart, the ADC need a little time to charge (It's a lot less than this, but its a good guide).
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Do you think that this might help? http://www.gammon.com.au/forum/?id=11916
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I think it has to do with a common ground.
Unless you post a schematic of your setup all we can do is guess and you wouldn't want that would you?

Schematic = answer
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I made two simple voltage dividers and they work great on either Battery or Solar Panel, but it gets real funny when I try to measure both at the same time. I think it has to do with a common ground. Has anyone managed to do this? Any ideas?

You got any code?
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Any ideas?   
Not without a schematic and code.
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The solar panel's voltage will drop in relation to the current being drawn from it. If you have it connected to the battery then the voltage will appear to be nearly the same as the battery.

As an addendum, measuring the voltage from a solar panel when it's not connected to any load is referred to as the "open circuit" voltage. Measuring that might be helpful in finding out the panel's peak voltage but it has very little to do with the panel's power generating capability.

The Wikipedia article on Maximum Power Point Tracking (MPPT) is helpful in explaining this behavior.
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I made two simple voltage dividers and they work great on either Battery or Solar Panel, but it gets real funny when I try to measure both at the same time. I think it has to do with a common ground. Has anyone managed to do this? Any ideas? 

Yes, we already gave you our ideas and we're waiting for you to do something
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it gets real funny when I try to measure both at the same time.

Funny "ha ha" or Funny "peculiar"?
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no schematic, no code , no answer
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11 replies and none from the OP.

Perhaps delay(48hrs); is needed?

...R
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