Grex Hardware Conference

View Responses

Grex Hardware Item 127: Data Loggers
Entered by rcurl on Mon Feb 24 17:14:15 UTC 1997:

Hardware and software for data logging with computers.

14 responses total.

#1 of 14 by rcurl on Mon Feb 24 17:24:54 1997:

I would like to log voltage over a period of ca. a day be means of
my computer. What is available, or what can I build, for doing this -
with a Mac, in particular. (I am looking in _Nuts and Volts_ at 
an advert for the "LPT:Analog!", a PC printer port A/D adapter, which
is built into a DB-25 connector, which looks like what I want, except it is
only PC compatible.)

#2 of 14 by n8nxf on Mon Feb 24 22:20:41 1997:

That's why I also have PCs.  There is a lot you can do with the parallel
port on those things.  It's also easy to write Basic routines on a PC.
The only thing I know of for the Mac is something made by National
Instruments.  Very expensive, as I recall.
 
In all honesty, this sounds like a good task for your XT.

#3 of 14 by scott on Tue Feb 25 02:09:52 1997:

You could try using the voltage to control the amplitude of an audio signal,
then feed that into a sound card...

I was looking at a new Jameco catalog at work today.  They had a nice
selection of stuff, probably all PC based.

#4 of 14 by arthurp on Tue Feb 25 05:06:08 1997:

The sound card idea is cool.

#5 of 14 by rcurl on Tue Feb 25 08:00:23 1997:

....back to the XT....amazing. But, I don't think I can get a sound card for
the XT.... Klaus, do you know of any other A/D like the LPT:Analog!, even
a kit? I'd think there'd be a chip that would do all this, and some
free/share-ware to run it. I've also thought that it should be easy to include
a parallel interface in a multimeter, but I haven't seen one offered.

#6 of 14 by n8nxf on Tue Feb 25 15:18:51 1997:

Yes, you can get a sound card in an XT.  At least an 8 bit unit...  Don't
try it thoug.  The input to a sound card is AC coupled and it won't see
a DC voltage, or low freq. AC.
 
Scott had a good suggestion with Jameco.  They have several kits, one of
which may well meet your application.  As I recall, they also had several
digital multimeters with serial ports.  I think Radio Shack also sells a
multimeter with a serial port.  Both should run with your XT and may come
with the required software.  I don't have the Jameco catalog with me today,
though I placed and order with them yesterday...  Perhaps scott, etc. has
their phone No. handy.

#7 of 14 by rcurl on Tue Feb 25 18:01:13 1997:

Yes, RS's "top" (and top $$) multimeter does have a PC interface (though
it doesn't take power from it for long term use). Actually, I wouldn't mind
having it - could use a multitester for C and L, at times. I'll check out
Jameco - probably they have a web site. Is there a "Stamp" application for
A/D conversion? I don't have the list.

#8 of 14 by n8nxf on Tue Feb 25 19:19:42 1997:

I think you could do it with a "stamp" too.  I have wanted to fool with
one of those things, but have not yet found the time or a project
important enough to justify the time ;-)

#9 of 14 by rcurl on Tue Feb 25 22:25:00 1997:

Well, here it is - an A/D interface to a Mac for you and me..  8^}
Jameco is on the web - in fact, their catalog is on the web. They have
meters with PC interfaces at about the RS cost. Did not see anything
more elementary, although there is a "microprocessor A/D chip" at a
reasonable chip-type price. MIght be the basis for...something...

#10 of 14 by gull on Wed Feb 26 06:43:40 1997:

You can get an 8-bit A/D interface for a PC for under $20.
They're sold as 'joystick ports.'

#11 of 14 by rcurl on Wed Feb 26 07:04:39 1997:

Any instructions on how to adapt that for data logging? I vaguely recall
seeing such written up (maybe in _Nuts and Volts_) but have no references
to it. That's the sort of thing I'd like to find. I suppose I could write
a BASIC program to do the logging (gosh, I used to know how to do that!).
Hmmm...  probably something out there on the web, under home automation,
for those that record temperature, light intensity, etc.

#12 of 14 by gull on Thu Feb 27 03:00:35 1997:

I think the biggest trick would be inputting the signal to the card -- it
expects to be measuring the resistance of the joystick's pots.  The cards
generally have four channels, X and Y for two joysticks; plus four on/off
switch inputs.  Most programming languages, including BASIC, can access a
joystick card one way or another.  I have a joystick port pinout somewhere
if you need it, I'd have to dig it up, tho.

#13 of 14 by rtgreen on Sun Mar 1 23:02:46 1998:

The PC joystick interface measures the time it takes to discharge a
known capacitor through the resistance of the joystick pot.  It's not
straightforward to condition a voltage to look like a resistance. 
Easier to go the other way...
  Do you have an old Commodore VIC-20 or C-64 laying around?  The
built-in joystick port on those machines is a real 8-bit a/d measuring
0-5v directly.  A simple voltage divider can adapt it to higher
voltages, and the port is easily read by the builtin BASIC interpreter.

#14 of 14 by arthurp on Wed Apr 15 04:48:31 1998:

Hmm.  I'm interrested in the same kinds of use of the joystick port.  It
has so be on a PC, though.  Any further developments?

Response not possible - You must register and login before posting.