[nSLUG] External temperature sensor (Gerald)

Rich budman85 at eastlink.ca
Tue Dec 11 16:58:32 AST 2007

Dop Ganger wrote:
> On Mon, 10 Dec 2007, Mike Spencer wrote:
>> I've been irritated for years that there was no similar, easy-to-use,
>> analog-to-digital port on a PC.  The joystick article seems to suggest
>> that there's a way to do this kind of thing after all without getting
>> onto the GPI Bus.
> It's not quite so simple. There's a bit of fiddling involved; from memory, 
> I had to read the port, wait for 10ms (ish?), and then loop reading and 
> waiting until the value changed and then the differential of the two 
> values was the analogue value being read. Once you've cobbled together a 
> routine to do that things are good to go. My only caveat is the Creative 
> Soundblaster PCI joystick ports were somewhat uncooperative. As Daniel 
> noted a thermistor is non-linear, I think I took around 20 readings to get 
> a reasonable level to alert on (this was for a server room to alert on 
> overheating).
> If you want to do a similar thing on the digital side the parallel port 
> works well. I helped build a two-person roller race setup using a magnet 
> and reed switch using two lines off a parallel port which did the trick 
> quite nicely for next to no outlay - though it was a pain hacking off the 
> end of an old printer cable and tracing each piece of wire because I was 
> too cheap to buy a plug and hood...
I remember adding a thermistor to show temps on my BBS when I had the 
Commodore 64/128 running.

Back in the good old days (BW-Before Windows),  my friend (who was good 
at electronics) and
I setup an interface to control stereo equipment to automate mass 
recording of DJ CD's (he worked as a DJ).
At first we used the serial port, but that limited us to one channel.  
So I explained how we
could use the parallel port interface.  He then picked up a few timer 
chips from Radio Shack
and bingo.   We also interfaced a third parallel controller (some cards 
were capable of
 the third address) to give us 16 inputs.

The system worked for many years - I think he still uses it from time to 
He eventually ported to Visual Basic.  I've been trying to get him on 
Linux. :)
No luck so far.

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