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precision voltage regulator adjustable

Discussion in 'General Electronics Discussion' started by Rajinder, Dec 4, 2016.

  1. Rajinder

    Rajinder

    344
    6
    Jan 30, 2016
    Hi all,
    I am looking to build a precision adjustable voltage regulator. I need to be able to control a voltage in the range of 5 to 10mV with great accuracy using a microcontroller. The other issue is that from the microcontroller I have a length of 2 core screened wire (around 500mm in length) going to the unit under test. So I might get some loss or fluctuations in my reading.
    Any ideas? I was thinking of PWM and low pass filter. Not sure though.
    Best regards,
    Raj
     
  2. Alec_t

    Alec_t

    2,569
    677
    Jul 7, 2015
    What % tolerance is acceptable?
    What resolution is required within the 5-10mV range?
    What load will the mV source have to drive?
     
  3. Rajinder

    Rajinder

    344
    6
    Jan 30, 2016
    The acceptable resolution is 0.25mV. with a tolerance of 5 percent.
    This is used to simulate a change of 5mV within a certain time to detect heat.
    The rare of change can then alert if heat has risen quickly indicating a fire.
     
  4. Alec_t

    Alec_t

    2,569
    677
    Jul 7, 2015
    In that case the PWM approach, with a precision potential divider, looks feasible; providing whatever the divider drives doesn't load it down beyond the tolerance.
     
  5. Rajinder

    Rajinder

    344
    6
    Jan 30, 2016
    Thanks for your help. So when you say potential divider I presume you mean a RC low pass filter?
     
  6. Alec_t

    Alec_t

    2,569
    677
    Jul 7, 2015
    No, I mean two resistors in series, with output from the junction. Your PWM will be putting out 5V (or 3.3V, depending on your micro's supply) pulses, so you will need to reduce that in order to get mV levels without resorting to absurdly small duty cycles. The low-pass filter could go before or after the divider. The division ratio needed would be around 1000:1 for a 5V micro supply.
     
    Last edited: Dec 5, 2016
  7. Rajinder

    Rajinder

    344
    6
    Jan 30, 2016
    Thanks
     
  8. TedA

    TedA

    156
    16
    Sep 26, 2011
    Raj,

    To really address your problem we need to know more.

    What sort of load must this voltage source drive?

    How much output current must it provide?

    Is the load resistive in nature? Or at least predictable?

    What do you have in the way of DAC or PWM outputs at your microcontroller?
    ( How many bits, voltage swing, Vref sources, etc.)

    Is there a Vref source in your system?

    Ted
     
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