Time between digital pulses on the parallel port

[DavidIMurray]

Hi

I am using the parallel port as a low cost digital triggering system for some labview code. We are using the port to trigger software that monitors a large rotating drum shear. Currently the rotation of the shear is detected by a single momentary contact microswitch. However the speed of the shear can vary so we are installing a second switch to monitor the speed.

I am basically looking to write a vi that gives a time between the first switch and the second switch being triggered but am having problems.

Any help would be much appreciated

Cheers

Dave

[KostasB]

Hi,

I don't have a lot of information about your application but I can give you some help on how you can measure elapsed time with LabVIEW. You can use a functional global variable (Measure Time.vi) to do that. See the attached

VI's. The Time Out indicator will display the time that the code was sitting in the while loop.

KostasB

NIUK Applications Engineering

Message Edited by KostasB on 06-18-2008 06:00 AM

[ShotSimon]

DavidIMurray,

Check out the Parallel Port Read and Write Loop.vi example that comes with Labview. 

You can also look through the forums there are many people using printer ports for all kinds of stuff.

You may also find these sites useful:

http://zone.ni.com/devzone/cda/tut/p/id/3466
http://www.doc.ic.ac.uk/~ih/doc/par/
http://et.nmsu.edu/~etti/fall96/computer/printer/printer.html

Note:  The third link has a simple circuit Fig. 3 with a push button switch connected to Pin 11 of the Printer Port.  You should be able to figure out a second input and then implement the timing between them as already explained.

You may need a few resistors (two 10k pull-ups) to your inputs switches and access to either your computers 5V supply or your own 5V supply.  I tested the circuit with the Labview example and it works.

Regards,

SS