DC motor speed control

[Kaunteya]

Hi there,

I want to control a DC motor with LabView. Both Switching ON/OFF and its speed control.

(I am using PCI-MIO-16E-4 (NI) card with SCB-68 (NI) board. I am using LabView 8.5 full development system.)

Attaching the VI, I am using for switching motor on/off; please guide me whether it is correct way or not.

Also, I am not getting idea as to how can I control motor speed? Because, if I generate analog output, how I can vary/control that output to match/vary motor speed.

Could anybody please guide me in this regard.

Thanks.

Amit

[Ian Colman]

Hi Amit,

You were definatly on the right tracks for turning the motor on or off using a digital output. I have made some small modifications to the front panel and the setup of the DAQmx Write VI as you can see. In its current state the program will provide a digital high or low on the line specifed on the front panel, as the button on the front panel is pressed. The problem is, it is very unlikely that you have a motor that is capable of running off the power supplied by your PCI-MIO-16E-4 DAQ card.

You will need some sort of buffer / external power source to provide sufficient power to the motor, rather than using this DAQ board as your power source.

As for speed control, you can either control the speed via an analogue output waveform that is buffered and used as armature voltage of the motor, or you can use a Pulse Width Modulated signal to control the effective voltage level that the motor sees. Both of these methods can be implimented using National Instruments hardware and software.

Could you let me know the nature of the motor that you wish to control and the application that it will be used for so that I can reccomend the best method of motor control for your needs please?

Best Regards,

Ian C
Applications Engineer
National Instruments UK & Ireland

[Kaunteya]

Hi Ian,

Many thanks for immediate reply and suggestions with the motor ON/OFF VI.

Thanks for correcting it, as now I got the idea, where I needed correction.

About the motor (which I want to control) and its application:

Currently motor is run by proper drive which powers it, but eventually we want to get rid of that drive so that we can control the motor independent of drive, solely on PC and LabVIEW.

Specifications of motor are:

Voltage: 220/240V

Current: 1.38/0.8 Amp

Frequency: 50Hz

Phases: 3

RPM: 3000

The motor is being used for generating vibrations for medical application,

therefore we need fine control over motor speed and its switching (ON/OFF).

Please guide me through the best possible way for it (controlling the motor).

Thanks and regards.

Amit

[Ian Colman]

Hi Amit,

Sorry I just posted a response and realised I needed to change the suggested information. Please bare with me whilst I look into this query further for you.

Best Regards,

Ian


Message Edited by Ian Colman on 04-09-2008 10:07 AM

[Kaunteya]

Hi Ian,

Many thanks, I shall wait.

Thanks.

Amit

[Ian Colman]

Hi Amit,

Okay there seems to be a bit of confusion here that I'd like you to clear up for me if possible. The all of your posts refer to the motor being DC, however it seems like the specs you gave are for an AC 3-Phase 50Hz Linear Induction Motor. It is fundamental to my hardware reccomendation that you can confirm the motor being used, whether it is AC or DC, maybe include a model number / manafacturer if possible so we can be absolutly sure of what is going on here. If you could let me know this I'll be more than happy to help you Amit.

Best Regards,

Ian

[Kaunteya]

Hi Ian,

I beg your pardon, I am not quite sure whether the motor is AC or DC,

I apologies for the heading of the posts, if it is wrong. The specifications which I mentioned are correct and manufacturer is VIBTECH, serial number being: 040261596.

The motor should be AC as the drive which I am using for it is AC drive for running 3-phase induction motor.

Does this gives you enhough/correct information to decide whether motor is AC or DC?

Thanks and regards.

Amit

[Kaunteya]

Hi Ian,

I am attaching data sheet of motor I am using, also attaching data sheet of controller/drive I am currently using to drive motor.

Thanks and regards.

Amit

http://www.vibtec.com/catalogue.htm

Message Edited by AMITNPUJARI on 04-09-2008 11:10 AM

[Ian Colman]

Hi Amec,

It does seem that your motor is a 3-Phase Linear Induction motor. This makes the situation more complex as National Instrumets does not have products to deal with 3-Phase induction motors directly. We have several great products to operate and interface with DC Servo Motors and Stepper Motors but you will need to use a 3-phase AC drive (such as the Vibtec VSC) to operate your 3-phase induction motor.

If this Vibtec control unit has any sort of electronic interface to accept commands from external sources, it may be possible use LabVIEW to write a program that interfaces with this drive and therefore your motor. I reccomend that your next course of action is to look into whether your drive can be controlled electronically, as unfortunatly it is not possible to directly interface with your induction motor using NI Products.

Please let me know your thoughts on this,

Best Regards,

Ian

[Kaunteya]

Hi Ian,

Thanks for information about all these interfacing. I suppose electronic interface is possible through controller drive (VSC) and SCB- 68 (NI) Board. And even if electronic interfacing is not possible on this drive, right now, we will try and buy the suitable one since we need to change the hardware according to interfacing requirements of LabVIEW. As using LabVIEW for controlling this and other parameters is our software plan.

Once I speak with my adviser on this issue of hardware interfacing, If I have any query then I shall post it immediately.

But, for the time being assuming that, we can control the motor electronically, could you please guide me through how I can precisely control the speed of the motor via LabVIEW programming.

Many thanks.

Thanks and regards.

Amit