Sensing Bidirectional Current With a Single Supply Op-amp

The circuit is essential the same as an operational amplifier in a differential amplifier configuration. The important difference is, instead of connecting the non-inverting input to ground, it is connected to a buffered voltage which is equal to half of your ADC reference voltage.

Bidirectional Current Sensing Schematic

Bidirectional Current Sensing Schematic

In software, you retrieve an unsigned value from the ADC register, copy it to a signed integer value and subtract half of the top value. For example, for a 10-bit ADC:

int MY_SIGNED_RESULT = ADCVALUE - 512;

If your ADC supports differential conversions, You can still use the above and save a pin; or you can direct VHALF into the inverting input and the op-amp output into the non-inverting input and convert with a signed result.

    • Sercan
    • December 16th, 2011

    Thank you for the post , very handy.

    • Taimur
    • November 24th, 2012

    Hello,
    This diagram is very helpful. I am working on kind of same thing. do you know how to calculate the values of resistors being used in this circuit if the sensing Resistor is 0.1ohm. That would be very helpful.
    Thankyou

    • VasiliSk
    • December 3rd, 2013

    Thanks!

  1. August 28th, 2014
    Trackback from : cheap games for wii u