# How do I wire an op amp to measure the difference between two solar panels?

I've been trying to hook up two solar panels as the inputs to an op amp LM741. My goal is to have the output be positive and saturated when solar panel #1 has light shined on it and the other doesn't. Then I want the output to be negative and saturated when the light is on solar panel #2 and not the first. I'm having trouble figuring out how to properly wire the circuit. Also, I've been using two 9 Volt batteries for my positive and negative power supply and where they meet as ground.

The voltage of each solar panel is 3V and I'm not clear on how to wire them correctly to compare their outputs using an op amp. Can you please explain in detail where the positive and negative leads of the solar panels should go for an LM741 with two 9 Volts batteries for the power supply.

• What happens when both panels are lit or both panels are unlit? You need to define all possibilities. – Andy aka Sep 13 '16 at 7:57
• While this would work, the traditional solution is to use two LDRs. But if you already have the solar panels and you're not restricted by size, then why not. – pipe Sep 13 '16 at 8:13
• Do the solar panels have a common ground? And what is the nominal voltage for each panel? – WhatRoughBeast Sep 13 '16 at 13:30
• Thank you for responding. The voltage for each panel is 3 Volts. And I'm not certain of how to wire them to an op amp so as to compare their voltages. Can someone please explain where the leads need to go. And instead of using words like ground please say between the batteries or whatever is most straightforward as possible. Thank you. – questionguy Sep 13 '16 at 16:19
• 'Ground' is an elementary concept in electricity. You can't just exclude arbitrary terms. – user207421 Oct 13 '16 at 20:18

1st define delta PV +/-max