Max 6675 Fluctuation values When using IOs on pic876


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  1. #1
    Join Date
    Jun 2011
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    Default Max 6675 Fluctuation values When using IOs on pic876

    Hi all,
    here is a triky situation,
    on a Pic 16F876,
    When using a digital Out pin to toggle an ON/OFF relay via a mosfet transistor (10K on Gate)
    the conversion of the (SPI) Max6675 ofset the Temp value to +8c, Why is that?

    is there any solution to this?
    The max6675 has a super stable 5V PS.

  2. #2
    Join Date
    Sep 2004
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    montreal, canada
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    Default Re: Max 6675 Fluctuation values When using IOs on pic876

    and the relay use the same psu rail?

    Would be great to see your code & schematic....
    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.

  3. #3
    Join Date
    Jun 2011
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    Default Re: Max 6675 Fluctuation values When using IOs on pic876

    Thanks Steve,
    I have a 24vdc/9A and 5/6A vdc power supply.
    I tryed all day to separate the PS of the relays by using regulator in series from 24v to 15v to 5v regulator to power the relays but same thing happened!.
    I have 6x 5v relays 4 analog pot, 4X servos, one pressur sensor (analog in), and one Max6675(3 i/o) on the Pic876.
    also the analog values are Ofsetting when the digital out are ON, the value on the TC is adding as the outputs are ON
    today I am going to try to split all the digital I/O's to a second pic.

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