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Hack $5.88 digital tire pressure gauge for computer input?

Discussion in 'Electronic Basics' started by Si Ballenger, Jul 17, 2005.

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  1. Si Ballenger

    Si Ballenger Guest

    I've noticed that WalMart has a small 5-99 psi digital tire
    pressure gauge for $5.88. Is it possible to hack one of these so
    that the output can be input to a computer fairly easily? I don't
    know what type of pressure transducer it uses so I'm wondering if
    anybody else has done any modification on one of these gizmos.
    Any info, data sheet sources, or web pages with info would be
    much appreciated! Thanks!
     
  2. Bob Masta

    Bob Masta Guest

    I know nothing about the particular model you mention, but I
    suspect that *at best* you might be able to find an analog voltage
    proportional to pressure in there somewhere. That's still a
    long way from being able to get it into a computer. The gizmo
    almost certainly doesn't have any sort of digital output that
    you can use, since it's made to drive only the readout. So you'd
    need some way to do analog to digital conversion. The only
    handly A/D most folks have is the sound card, but the problem
    is they don't respond down to DC, which you need for standing
    pressure. You could take the voltage and chop it into a square
    wave with a simple analog switch and oscillator, at say 1 kHz or
    so, and then the sound card could read it. Then you would have
    to write code to extract the level of the square wave from the
    digital signal. If all that still seems "fairly easy" you might take
    a look at it. But remember, I said *at best* there might be an
    analog signal in the pressure gage.... it's also perfectly possible
    that the internal A/D is tightly bound up with the processor via
    a charge balance routine or something.

    Best regards,


    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Home of DaqGen, the FREEWARE signal generator
     
  3. Randy Day

    Randy Day Guest

    [snip]

    If the LED/LCD signals aren't multiplexed in some fashion,
    another possibility might be to tap off the LCD pins
    and decode the segment combinations back to digits.

    It might not be simple, pretty or even possible, but
    it's something to explore.
     
  4. Jon Danniken

    Jon Danniken Guest

    How about using a VCO from the analog voltage into the sound card?

    Jon
     
  5. Guest

    A DS2438 http://pdfserv.maxim-ic.com/en/ds/DS2438.pdf might be useful,
    it would connect serial port.
     
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