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List:       suse-linux-uk-schools
Subject:    [suse-linux-uk-schools] Datalogging
From:       Richard Rothwell <raroth42 () yahoo ! co ! uk>
Date:       2003-05-14 14:26:22
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> 
> Not aware of any school friendly robotics or data
> logging stuff for
> Linux. 

I've been playing around with a design for a low cost
one channel datalogging system, which would be ideal
for a simple C project.

Outline concept is this...

Sound card is used to generate an AC signal which is
conditioned to 0.7 volts (using a diode and resistor)
which is then split across a potential divider - one
side of which is fixed resistor other side is
thermistor / LDR.  

Stereo mike input is then used to compare the voltage
across the whole PD with the voltage across the
thermistor / LDR.  

Data logging process is simple - write to a file of
fixed maximum size with initial sampling rate.  If the
file fills the sample rate recursively halves.  This
program could be as simple or as complex as you want.

Total component cost less than £2 for a basic hard
wired system.  Maybe take it up to £5 with boxes and
variable resistors for a device that will use
different sensors.

Anyone fancy doing it with me? I can draw the circuit
idea out in a few mins.  Some expert can write the
code and I'm not good with a solering iron, but could
do it...

=====
rgds,
Richard Rothwell
--------------------------------------------------------------------
GNU and Wine are rirds.
Rird is recursively defined.

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