Help with a 4th year project: Control a 3 phase motor and convert input voltages into pressure values

[grantstephen]

Hi,

I'm in my 4^th year at university and I have been given a project that involves the experimental investigation of the interaction between fishing gears and the seabed. The work will consist dragging full-size or scale trawl components along a channel containing typical seabed sediments. I aim to create a LabView program that will allow me to operate the motor and analyze the 6 transducers I will be using.

For the motor I desire to be able to:

1 - Start the motor.

2 - Define the speed it accelerates to.

3 - Have the ability to switch off automatically depending on its speed and distance it has to the end of the rig to avoid the trolley crashing.

For the 6 transducers (4 pressures, 1 load cell, 1 horizontal displacement) I desire to be able to:

1 - Convert the voltage signal into the relevant unit of measurement.

2 - Record data at a rate of 10Hz.

3 - Output the recorded data into a file and also onto graphs.

I also intend to introduce an emergency shut down facility for the whole system.

I have started doing the built-in tutorials so i am able to do the basic routines. However I have no idea where to start creating a program to control a 3 phase motor and to be able t convert voltages from transducers into pessures and distances.

I have version 8.5 if anyone has any information or advice i would greatly appreciate it .

Thanks,

Grant.

[jon_mcbee]

I believe that how you control the motor will have much more to do with the motor itself than labview.  For instance, the motor could be driven with relay switches that give voltages to certain inputs that correspond to certain actions of the motor.  In this case all that labview needs to do is control the relay module.  I guess what I am getting at is if you can provide more details about your setup then people will be better able to give you an idea of what you will need to do with LabVIEW.

Cheers!

[mike72903]

Grant, converting voltage and or current outputs of transducers to engineering units is  done with simple math.  Commonly called MX+B functions.  You will need to know the M and B values.  X is the input value from the transducer.  I am presently working on a project that requires reading pressure transducers that output 1 to 5 volts over a range of 0 to 500 psig.  In this example the M value would be 125 and the B value would be -125.  The 125 M value is the transducer range of 500 divided by it's output range of 4 volts (5-1).  Since multiplying 125 x 5 = 625 you must subtract (or add a negative in this case) to get 500.  So 1 volt output is 1 x 125 +(-125) = 0psig and 3 volts output = 3 x 125 +(-125) 250.  In the case of a transducer with a 0 based output (say 0 to 10 volts over it's range) the B value would always be 0.  All this assumes you are using amplified transducers with a linear output over their range.

[grantstephen]

This information is very helpful.

I'll be intouch wrt to how the motor is set up and hopefully I can start making some headway with my project.

Thanks again.

[mike72903]

Glad to help.  BTW, Im no lv expert, but writing to files and also to graphs is very simple in lv.  lots of good tutorials and samples available through the help menu.  Take note that graphs and charts are different things in lv.  Just in case you need to plot real time data, charts are what you want to use not graphs