A post here INA219 sensors and measure of the solar panel and lead acid battery has asked about using INA219's to monitor a solar charge controller using the following circuit:
Post a real schematic to see the system details.
The conclusion was that the INA219 cannot be used to measure the solar panel voltage, with that particular type of controller.
As pointed out, the panel voltage is not needed.
So, suppose, just for a moment that I DID want to be able to measure such a voltage, are there any sensors to do such a thing?
A voltmeter, connected across the panel terminals, comes to mind.
And how would I connect that to an arduino, or are you just being awkward and obtuse?
That would depend on which voltmeter, and which Arduino you chose.
For informed help with your project, please read and follow the instructions in the "How to get the best out of this forum" post, linked at the head of every forum category.
@frank18
In addition to posting a real schematic of your project you need to post the link to your positive ground charge controller. Also post the model of your microcontroller and descriptions of any sensors and peripherals you intend to use.
A charge controller like the one in the linked topic requires special attention if any measurements are to be made on it.
`
real schematic of your project
`
Impossible to do that when I don't know what sensor I could use to be able to do what I want. I guess I'm asking in the wrong place.
So you have no idea which charge controller you have or which microcontroller you have? If that’s the case you can start from scratch and use a charge controller that is not common positive.
The correct way to start a project is to draw a schematic diagram of the parts you think you might need. You can put part numbers on them after a little discussion and thought about that.
If you’ve come here without any idea at all just wanting the forum to hand you a complete project then you need to offer to pay someone to do it.
I came here to simply ask if there is a sensor that can be used for low-side. Unfortunately everyone in this forum just jumps on their high horse and takes the {redacted} attitude to new users that is taken everywhere here. If I'd spent five minutes looking though the forum before asking that would of been obvious.
moderator edit: language
Please delete this account as even that doesn't seem to be possible from my profile.
The simple answer is “Yes you can do it with an ARDUINO programmed to be a voltmeter.” Happy?
P.S. From your avatar, I can see why you’re so angry.
So I was wondering before so-very-angry left us if it wouldn't be possible to measure the "positive ground" referenced voltages by completely isolating the Arduino with relays and never having the Arduino ground common to more than one voltage source at a time. That wouldn't require a special sensor but would accomplish OPs initial requirement. Connecting sensors like the INA219 to measure current would be a different problem.
I thought there might be a way to power a microcontroller off the positive ground system but didn't think that through.
The basic problem with measuring the solar panel voltage is that most charge controllers use PWM switching.
So the measured "panel" voltage levels are either open circuit, which is uninformative because it doesn't depend strongly on illumination level, or the battery voltage, during alternate portions of the switching cycle. Either way you don't learn anything very useful about the solar panel performance. Only the current matters.
Whether the ground is positive (true for many older controllers) or negative is a separate problem.
Okay, I get it. It doesn't particularly matter how one would do it then.
the amount of time and effort required makes these
a no brainer imho
every stat under the sun at your finger tips
Displaying generated panel power could be nice.
The INA219 should be able to output power from it's measured battery voltage and panel current.
Leo..
Hi,
In your schematic.
You have the potential to apply more than the 5V or 3V3 that the A0, A1 or A2 is rated at.
Can you please tell us your electronics, programming, arduino, hardware experience?
Tom.. 
Way more. 
