Isolated Voltage Measurement with Atmega8

Discussion in 'General Electronics Chat' started by adamj12b, Aug 4, 2009.

  1. adamj12b

    Thread Starter Member

    Mar 3, 2009
    Hi guys,

    Im having some trouble coming up with a circuit to get an isolated voltage measurement into an atmega8 micro-controller.

    The device is a high power motor controller that is running at 144VDC from a battery pack. The control section is isolated from the main battery, running from a 12V battery. I need to be able to be able to read the voltage of the high voltage battery while maintaining the isolation.

    A few things I have considered are liner optocouplers, and a voltage to frequency converter. I would like it to be accurate as well.

    Im not sure how I would go about using the linear optocoupler for the voltage measurement, but with the frequency converter, I would just convert it, then opto-isolate it then feed it into the controller.

    Any Ideas?

  2. John Luciani

    AAC Fanatic!

    Apr 3, 2007
    Have you looked at the isolation amplifiers from Analog Devices and Texas Instruments?
    Checkout the TI ISO122 and ISO124. These parts are are in DIP packages and are
    in the $20 range.

    (* jcl *)
  3. hgmjr

    Retired Moderator

    Jan 28, 2005
    Depending what constitutes "accurate" for you, the use of a voltage to frequency converter followed by an opto-isolator the output of which is fed into the ATMEGA8. The "input-capture" feature present in the AVR should work just well for determining frequency.