get motor position in velocity mode

[mj23]

Hello! I'm a beginner working with LabVIEW and I need to control a DC motor. I'm working with this motor on velocity mode and i want to get and display his position.  How can i get the motor position? I found a VI (read position.vi) that gaves me the position but it dosen't work in velocity mode...Is there any simple away to get the position of the motor on velocity mode?

Thank you.

[Olivier_L]

Hello,

Could you be more precise on what you want to do, and which material do you use? type and informations about your motor, which type of sensor is used to control the position or the velocity?

What do you mean by "velocity mode"? and where did you find the "read position.vi"? could you attach it in the forum?

Thanks.

[mj23]

Hi

The motor that i'm trying to control is a stepper motor and i have a NI 7314 PCI board to do this control. In the NI 7314 PCI board's software there's a VI where  we can  select  between  the velocity mode  and the position mode operation to control the motor.  My doubt is if exist in the control library of the NI 7314 PCI board some away to get the motor position when i'm working on velocity mode.

Thanks 

[Jochen]

The PCI-7314 is a quite old motion control board and part of the ValueMotion product family which is obsolete for several years now. The ValueMotion product family lacks some important features. It's entirely possible, that you can't read back the position of the motor, when itthe axis is configured for velocity mode.That's the reason why NI has discontinued this product family quite quickly after buying NuLogic, who has developed the ValueMotion and the FlexMotion boards.

FlexMotion boards are much more powerful and NI has developed three product groups out of this product family:

NI 7350 
NI 7340 
NI 7330 

While the 7340 and 7350 boards provide support for servo and stepper motors, the 7330 is a low-cost stepper controller. The PCI-7334 is a direct replacement for the 7314 and is based on the superior FlexMotion architecture.
The disadvantage of switching to the 7334 is the fact, that this board is not pin compatible or software compatible with the 7314, so some rewiring and recoding would be required.
I still recommend exchanging the 7314 with a 7334 because this board has several advantages. Here is a selection:

• long-term driver support for current operating systems (VISTA-support)
• long-term availability
• superior step generation algorithm (time-borrowing algorithm for smooth acceleration ramps)
• superior hardware architecture and a much better feature set

I hope this helps,

Jochen Klier
National Instruments