Isolated Voltage Measurement with Atmega8

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

  1. adamj12b

    Thread Starter Member

    Mar 3, 2009
    15
    0
    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?

    -Adam
     
  2. John Luciani

    Active Member

    Apr 3, 2007
    477
    0
    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

    Moderator

    Jan 28, 2005
    9,030
    214
    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.

    hgmjr
     
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