[OT] Engine temp sensing (was: Re: [plug] VW parts was: Hack, triplej and open source)

[Harry]

On Thu, 01 Jul 2004 15:48:29 +0800 Michael Hunt <michael.j.hunt at usa.net>
wrote:

> To bring this post back on topic I'm trying to figure out a way I can
> log (preferably to my Linux laptop) my engines oil temperature (say 30
> sec intervals) over a long journey (say an 1 and half hours). VW motors
> are supposed to run optimally at an oil temp of about 125 C, but I think
> mine is running hotter. (At the moment I'm not exactly sure what the
> temp is as I have no oil temp gauge).

I know I'm letting the side down here but what about a real time optically
coupled South American aftermarket oil guage with adaptive sampling rate
(basically when you glance at it) ? ;-P

> As a little project I was thinking I might try and rig up a temp probe

Here's the rub. You will need a sensor that goes to a bit more than 125C
and most of the little i2c temperature sensing chips won't hack the
temperatures you are running in the VW engine environs. A thermocouple
or similar high temp sensor is probably what you need. These can have
interesting non-linear behaviour; all fixable with some software
calibration which you could achieve using an existing temperature guage ..

Um .. try instead looking at the dallas semi data (now part of maxim).
IIRC they have little devices to interface things like thermocouples to the
i2c buss with on-board calibration. Or maybe Analog Devices.

http://www.maxim-ic.com/
http://www.analog.com/

*looks*
http://www.maxim-ic.com/products/sensors/thermocouples.cfm

Hmm. No they have SPI and pulse width modulated output; not i2c.
You'll need a little PIC or similar MCU to convert one to the other or SPI
to RS-232 is probably easiest so you can just grab the data through your
serial port. Make the PIC spit a sample ever 30 seconds or whatever and ..

.. in linux:

$ stty -echo < /dev/ttyS0             (set baud rate and things here too)
$ logger -t vw_oil < /dev/ttyS0

So each sample is time stamped and stored in syslog .. too easy.

CPAN has examples for using Parse::Syslog to fetch your vw_oil lines from
syslog. You will need:

apt-get install libparse-syslog-perl

Data acquisition for fun and profit and the good oil on the VW engine :-) 

All the best
Harry

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