Hack $5.88 digital tire pressure gauge for computer input?

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!

 

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

 

[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.

 

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

Jon

 

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