uln 2003

[macbett]

Hi;

I wanna control a stepper motor with uln 2003 by lab view 7.0. What can i do.

Thanks...

[DJ_L.]

Hey macbett,

How are you planning to send your TTL signal to the ULN2003? First, I would point you to the document called the Fundamentals of Motion Control. There are many other document links on this page that are an awesome resource, such as the Basics of Stepper Motors and NI SoftMotion: Create Your Custom Motion Controller on Any Platform with LabVIEW.

So to answer your question, "what can you do?" you have many options with how you can control your stepper motor. A lot depends on what hardware you have and what you want to use. You can purchase one of NI's Motion Controllers to control the stepper, and the motion controller takes care of a lot of the details for you, making it easier and faster to get up and running. Or if you want to use some kind of digital output board, then you could use for example an NI DAQ board, but you would have to know how to send signals and how to the ULN2003, so that it can amplify the signal to send it to your motor. Last, maybe you have some kind of microprocessor that sends digital signals to this ULN2003, and in this case you would have to know how to communicate with the processor. With these options that you have, they each have a different way to work with LabVIEW. For example there are NI-Motion (driver) VI's specifically for controlling motion using NI's Motion Controller. There are specific DAQ (driver) VI's for controlling what comes out of the DAQ board. And there might be some 3rd party instrument control to talk to a processor - which would have VI's in LV. Also, you need to consider if you are going to treat the stepper as an open loop stepper or a closed loop stepper. If you need it to be closed loop, then you need to know how you are going to get the Feedback into your system somehow, and if your program needs that feedback, how to get LV to recognize the feedback. So to sum up you have many options of how to do this, it is really dependent on what and how you would like to do it. First, make sure you know how an overall motion system works, and then go from there.

I hope this answers your question, or at least points you in the right direction to start making some decisions of what you would like to do. Please let me know if you have any questions. Thanks, and have a great day.

Regards,

DJ L.

[macbett]

DJ L. Hi;

I found a example (Parallel Port Read and Write Lop.vi) in LV 7.0. But i cant make what i want. I wanna send 1,2,4, and 8 signal to parallel port on for loops.

Thanks...

[DJ_L.]

Hey macbett,

So if I understand you correctly, you are just using your parallel port on your PC to send signals to this ULN 2003? If you are, are you having a problem with just writing values to the parallel port? Please explain what you are trying to do in more detail, and describe what you mean when you say: "send 1,2,4, and 8 signal to parallel port on for loop". The more you can explain, the better others on the discussion forum can help you out.

Let me know if you have any questions. Thanks.

Regards,

DJ L. 

[Buechsenschuetz]

The ULN2003 is a simple darlington transistor array and (sometimes) used as the last part in a chain to drive a stepper motor. When you want to send digital (TTL compatible) pulses to the ULN2003 you can switch on and off the winding but you cannot do any current regulation.

The latter is essential if you want to use the drive in microstep mode, as you probably will. Using a stepper motor in full step mode only (i.e. switching on and off the windings in a certain sequence) results in very rough operation, and of course position control will never be more precise than the full step rate of the motor.

Usually you need some interface between a digital control system and the output driver to do microstepping. Such controller ICs (sometimes with more or less powerful driver transistors on chip) are widely available. However, to do proper current regulation and control you will need quite a bit of design work (and experience). In most cases it is easier (and of course much quicker) to use a ready-made motor driver module which allows for microstepping, current regulation etc and can easily be driven with digital pulses.