digital thermometer without microcontroller

Discussion in 'The Projects Forum' started by pinktoadette, Apr 29, 2015.

  1. pinktoadette

    Thread Starter New Member

    Apr 29, 2015
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    is it possible to do this without a microcontroller?

    I would like to use lm34 with 4 digit 7 segment display.
    looked around and i know i need an analog digital converter. But if that's all i need, why do i need a full microcontroller like some of the projects out there?
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,153
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    Just get a voltmeter with those specs.

    Example (not an endorsement!)

    If you need to scale it differently, you could add an op-amp circuit in between, to convert the LM34 output into a different voltage range.
     
    Last edited: Apr 29, 2015
  3. pinktoadette

    Thread Starter New Member

    Apr 29, 2015
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    not quite what im looking for... whole point is to make it myself
    i guess i'll stick with the microcontroller..

    thanks
     
  4. #12

    Expert

    Nov 30, 2010
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    That's the way the world is going right now. Better to program a microcontroller than to learn how to fit two ICs to a display driver.
     
  5. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    How about an ICL7106 or 7107?
     
  6. #12

    Expert

    Nov 30, 2010
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    I am corrected. Fit one IC to a display.
     
  7. takao21203

    Distinguished Member

    Apr 28, 2012
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    it needs many discrete parts and the display must match
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Among other tings, the microcontroller converts the straight binary out of the A/D to binary-coded decimal (BCD) for the displays. The output of a typical A/D converter is a single word of 8 to 16 bits that represents the analog value in straight binary. A multi-digit display needs 3 or 4 bits for each digit to display the values 0-9. For example, a 12 bit A/D can output binary values that represent to 4095 in decimal. To drive 4 decimal digits takes 15 bits in BCD.

    As noted above, there are BCD-coded A/D converters specialized for the digital panel meter market. With an opamp or two for buffering and scaling, they will do exactly what you want.

    ak
     
  9. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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  10. absf

    Senior Member

    Dec 29, 2010
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    Should be possible. LM35 output 10mV per degree C, i.e. 1000mV = 100°C. But then just the ADC chip alone would cost many times more than a cheap PIC uC. Not to mention the convert-display logics to convert Binary to BCD and decode them to 7 segments displays.

    A cheap 16F 18-pin PIC would cover all of that provided you already know how to use it.

    Allen
     
  11. Søren

    Senior Member

    Sep 2, 2006
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    The CA3161/CA3162 is good for 3 digits, which should do for most things.
    But they may be as scarce as the ICL voltmeter IC's and hence carry a ridiculous price tag
     
  12. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    You can get a simple panel meter. Some panel meters can be configured to place the decimal where needed for a given input range. All for 5 to $20 - depending on quality and store.
     
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