Input to Arduino

Discussion in 'Embedded Systems and Microcontrollers' started by tas99, Mar 5, 2013.

  1. tas99

    Thread Starter New Member

    Feb 25, 2013
    Title is not very descriptive because of problem starting new thread

    I’m using a circuit I found here in another post (see attachment) to measure the current from a solar panel and feed that data to an analog input of an Arduino.
    The panel produces about 1 amp max resulting in about 100mv across the sense resistor and this is pretty small to get any kind of resolution out of the Arduino so I’d like to amplify that voltage to 5V as 1 amp flows through the sense resistor. I was thinking of using something like an LM 358 opamp (I’m planning on powering it with 9V so I don’t have a + and – supply) in a non-inverting configuration but I’m not sure how to design the circuit.
    I’d appreciate any help on this or a better idea if someone has one.
    Thanks in advance,
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Hey Tom, good question. It has a nice answer too, that being a "high side current sense." Google that term and you get links to several manufacturers with lots and lots of devices that take a very small voltage across a resistor and amplify it for a micro controller's A2D input (which expects the signal reference to ground). You can find them with fixed gains or adjustable gain set by resistors.

    "High side" means the resistor sits in the positive line, not the negative. If you ever get into solar power for buildings where the electrical code comes into play you'll find you cannot put sense resistors in the negative side (it's a direct code violation) so you might as well start off doing it "the right way."