Newto NI: Options for doing this job

[MickyM]

Hello Everyone!

My name is Micky and I am a Mechatronics Engineering student at UNB (University of New Brunswick, Canada). I am just starting out with Labwindows and NI's hardware for some of my projects. I am indeed very happy to see such a wonderful and expert community.

I am workig on a project and I am a bit confused as to the approach. Here's what I have on hand:

There is a disk with 22 slots on it(like a roullette wheel and then covered by a disk...so basically two disks 1" apart with 22 pockets).This is mounted on a shaft. All this is housed in  a box with an opening the size of the slot opening on the disk.
I need to :
1. Rotate the disk so that each step is one slot >> approx 16 deg and then execute a bunch of commands.
2. Time interval of about 3-4 hrs
3. Rotate again 16 deg to align the next slot opening on the disk with a external opening on a box
4. Continue untill the 22 slots

Now my approach is this:

1. Have an optical encoder on the shaft.
2. Use a DC motor to turn the shaft in conjuction with a gear set(to reduce the speed)
3. Use A CNZ1021 transmissive photosensor to count the number of edges(in conjuction with the encoder above)
4. Then program the logic so that :
     The motor starts at count 0
     then stops when the count = # counts that equal to 16 deg rotation
     then wait for 3-4 hrs
     then again start the motor and run till the total is now equivalent to 32 deg...and continue untill all 22 slots i.e 360 deg rot

Or use a stepper motor to do the same task.

Please advice what you think is a better approach. I have no knowledge of working with stepper motors but will learn if it is a better option to wht I have in mind.

Thanks for all your help and time.

Micky

[Jochen]

Micky,

for this task a stepper motor should be a better choice. If you size it correctly, you even could run it in open loop without any feedback device. No tuning is required for steppers and as I can't see a need for very high velocities or things like dynamic torque adjustment, a stepper motor should be a good fit and the system setup and configuration is much easier.

Regards,

Jochen Klier
National Instruments

[MickyM]

Jochen, thanks for your reply.

Couple of questions:

Right now we are using:
1. LabWindows 8.5
2. PCI6035E
3. CB  68-LP connector block

What else would I need to use the stepper motor as you suggested?
Also, is it possible to just program a PIC using LabWindows (Any example etc)

Thank you very much and have a wonderful day!

Micky

[Vivek_N]

Hello MickyM,

You should be able to drive the stepper motor using the output of the DAQ card, provided the current required to run the motor falls within the range of the current output of the DAQ card.

If the current needs to be amplified, a stepper motor driver is required. There are many stepper motor driver ICs available, so you will have to choose one corresponding to the input required for your motor.

To answer your other question, here is some information that should answer your question: LabWindows/CVI is an ANSI C Compiler. If the PIC that you are using is ANSI C compatible, there is a chance that it will be able to run the code that is compiled. You can check if the PIC is ANSI C compatible from the datasheet. However, there are lot of low-level calls which may not work as the CVI compiler will compile for an x86 computer (like PCs). The compiler that comes with the PIC, on the other hand, will surely work  as it is familiar with the architecture of the PIC.

I hope this helps!