PLC control of single axis stepper

Hello,
First off I'm not an experienced PLC programmer But I have been using a single axis stepper controlled via a PC for 6 years or so. The vendor of the current system I use has gone bug nuts unreliable so it is time to move on.
I think that for a PLC my needs are pretty simple. Even from a beginner stand point writing the ladder logic should be pretty simple as well. At least I hope so.
3 buttons and an on the fly speed control. 1 button CW rotation, another CCW rotation and the last is a stop button. A potentiometer for speed control.
I would like to do one stop shopping if possible and have found the motor that will do the job at automation direct. It is a
STP-MTRH-34127D NEMA 34 DOUBLE SHAFT 1290 oz-in BIPOLAR


and this for the driver:
STP-DRV-6575 STEPPER DRIVE 7.5A 24-65VDC 2-PH BIPOLAR MICROSTEPPING



Right off I don't see a need for an HMI. Max and min velocity would be set it the PLC and the pot would allow manual change inside the set limits. Would also be a good idea to have limit switches.



Any suggestions on a PLC for this application? Right now I see dozens upon dozens, each with unique abilities. I have hours spent reading on spec sheets but am no closer to having a glue as to what one to try and start with.


Thanks in advanced for any input.

To me if you have gone down the automation direct route perhaps you should stick with them. I haven't had the experience with their PLC products but I have been intrigued. My company uses allen Bradley, square D, and Fanuc Products however automation direct has impressed me on their quality. The HMIs I have used through them have been the best designed I have encountered. Their programming software is reasonably priced(hundreds not thousands)and have not had a single problem with their software. A low priced competitor Eurospec Direct also sells proximity switches. I purchased about 30 ...I probably have replaced 28 of them so far with the Automation Direct version because the Eurospec Direct ones failed.

Well it is not cast in stone that I deal with automation direct, it just looked like a good place to start. With more reading l find that using a PLC to read analoc from a pot gets messy in ladder logic. The use of a special l/O that coverts the analog value would be needed.

I've used quite Automation Direct quite a bit and don't see a problem with them especially if you don't need a ton of bells and whistles and you'd like to keep your budget down. Only thing that sticks out is you said you want to change max and min speed with the plc. Do you plan on doing this with physical inputs or are you thinking of communicating with the stepper? I think you'll need the Sure Step Advanced drive (STP-DRV-4850) if you plan to do communications from the PLC.

Does the PLC need to see the information? I've got two type of drives at my plant. We have the PLC controlled ones that usually involve automatic linear motion then we have what I call "dummy drives". The "dummy drives" can be enabled by the plc but their parameters are preset. That is parameters except for speed. This is done at the drive or if the parameters are set correctly with a potentiometer. If nobody is just "trying something new" then I would guess 80 or 90 percent of the time this is how it is done.

I'd use COPLEY for the stepper drive, and connect it to a ProFace all-in-one HMI/PLC over CAN bus.
Not has hard as you might think, and really really thrifty (i.e. inexpensive, i.e. cheap)

dginbuffalo said:

Only thing that sticks out is you said you want to change max and min speed with the plc. Do you plan on doing this with physical inputs or are you thinking of communicating with the stepper? I think you'll need the Sure Step Advanced drive (STP-DRV-4850) if you plan to do communications from the PLC.

Click to expand...

Hi dginbuffalo,
Thanks for the input, I'll look over the advance drive. If you don't mind I'd like to ask a few more questions on the speed control issue.

You asked "Do you plan on doing this with physical inputs or are you thinking of communicating with the stepper?"

That question itself leaves me wondering about other options to achieve what I need done. I'm painfully aware that my minimal at best knowledge can lead down the path of a poor performing design.

OK, so the part about physical inputs, right now I have a stepper that I can vary the speed on the fly via a simple keyboard command. Press one key and the step rate increases a fixed amount. Press another and the step rate decreases. The amount of change is fixed so to slow down from 2700 sps to 250 sps takes a few seconds of holding the "slow down key".

To me it does not matter how the control input gets to the stepper. If a CLEAN system would use a PLC to read limit switches, set rotation direction and another device was used to change the pulse frequency to the stepper in real time by manual input from the human machine operator then I'm open to all input.

GlenGineer said:

Does the PLC need to see the information? I've got two type of drives at my plant. We have the PLC controlled ones that usually involve automatic linear motion then we have what I call "dummy drives". The "dummy drives" can be enabled by the plc but their parameters are preset. That is parameters except for speed. This is done at the drive or if the parameters are set correctly with a potentiometer. If nobody is just "trying something new" then I would guess 80 or 90 percent of the time this is how it is done.

Click to expand...

Hi GlenGineer,
OK with my first post I thought why bother with all the dull details of my equipment, but maybe that would be best.

The stepper motor is used to lift and lower parts into a process tank. The motor lives on top of a gantry that travels back and forth some 20 feet to selected process tanks. The stepper does it's work through a worm gear driven winch. So brake feature is automatic through the worm gear. The travel distance of the part being lowered / raised is no more than 40 inches.

In general lowering the parts into the tank needs to happen as quick as possible. HOWEVER, many parts have shape issues that require the insertion speed to be slowed down at a critical point in the travel and then the speed increased back up. A human operator has to make the judgement call each time the part is lowered.

That is the key issue. Otherwise I could run with two fixed speeds. Fast CW for insertion and slow CCW for extraction.

Just blue skying, but a small operator panel with a speed pot that generates an anolgue signal, like this one, http://www.divize.com/current-loop/a2007e-sp.html along with whatever switches and lamps you want, and an
analogue CLICK, Sure Step combo would get you where you want to be. You would have to setup your ASCII message to include the analogue input scaled/converted to the right values so the drive could read it, but that is certainly doable. Heck you could go whole hog and add an HMI.

dginbuffalo said:

I've used quite Automation Direct quite a bit and don't see a problem with them especially if you don't need a ton of bells and whistles and you'd like to keep your budget down. Only thing that sticks out is you said you want to change max and min speed with the plc. Do you plan on doing this with physical inputs or are you thinking of communicating with the stepper? I think you'll need the Sure Step Advanced drive (STP-DRV-4850) if you plan to do communications from the PLC.

Click to expand...

Thanks for the tip.. looks like the STP-DRV-80100 is the same thing but has the amp rating to handle the 34127D's motor coil.

So I can use buttons to the PLC to set direction and a speed and a potentiometer to the driver to vary the speed on the fly.

Stepper

Hello,

I agree the Click plc is probably your best option seeing you have limited experience. I have used the high speed counting cards (CTRIO /CTRINT) with the DirectLogic and Do-More PLCs. There are several videos on the Automation Direct web site to walk you through using the Click plc or the CTRIO high speed counting card. If you are looking for position feed back then the high speed counting cards are your option.

Below is a link to the videos by Automation Direct.

http://www.automationdirect.com/adc...Systems/Stepper_Drives_-z-_Power/STP-DRV-4850

Hope This Helps
Tom

The AutomationDirect DL-05 and DL-06 both have stepper control built right into the brick. They will drive pulse and direction without any additional hardware, other than the drive. Those bricks even have a (very) simple motion controller feature that are good f0r simple positioning.

http://www.automationdirect.com/adc...ogic_05_(Micro_Brick_PLC)/PLC_Units/D0-05DD-D

http://www.automationdirect.com/adc...andable_Micro_Brick_PLC)/PLC_Units/D0-06DD1-D


I've done exactly what you're describing - CW and CCW with analog speed control - with the '05 before. I've also done a positioning application with the '06. The only difference between the '05 and the '06 (besides more I/O on the '06) is that the '06 has a higher maximum output frequency (7KHz VS 10KHz), so you can drive your motor at a higher RPM, if that's important.

You will need an analog input card for either of those PLC's. 0-10V is easiest to use with a simple pot.

http://www.automationdirect.com/adc...dable_Micro_Brick_PLC)/Analog_I-z-O/F0-04AD-2

The manual is actually very good at describing the ladder logic setup for controlling the stepper. Ask more questions if you decide to go this route. I'll chime in with what I know.


-rpoet

rpoet said:

The AutomationDirect DL-05 and DL-06 both have stepper control built right into the brick. They will drive pulse and direction without any additional hardware, other than the drive. Those bricks even have a (very) simple motion controller feature that are good f0r simple positioning.

http://www.automationdirect.com/adc...ogic_05_(Micro_Brick_PLC)/PLC_Units/D0-05DD-D

http://www.automationdirect.com/adc...andable_Micro_Brick_PLC)/PLC_Units/D0-06DD1-D


I've done exactly what you're describing - CW and CCW with analog speed control - with the '05 before. I've also done a positioning application with the '06. The only difference between the '05 and the '06 (besides more I/O on the '06) is that the '06 has a higher maximum output frequency (7KHz VS 10KHz), so you can drive your motor at a higher RPM, if that's important.

You will need an analog input card for either of those PLC's. 0-10V is easiest to use with a simple pot.

http://www.automationdirect.com/adc...dable_Micro_Brick_PLC)/Analog_I-z-O/F0-04AD-2

The manual is actually very good at describing the ladder logic setup for controlling the stepper. Ask more questions if you decide to go this route. I'll chime in with what I know.


-rpoet

Click to expand...

Hi rpoet,
Thanks for the input. I'm going to look over the specifics on the items you linked to and get back on track with this project.

I'll second Copley as having excellent stepper control for less than you'd expect.

As far as recurring costs, the lowest end stuff from several PLC makers (micro820 from AB, X20 Compact CPUs from B&R, etc) can compete with Automation Direct. The Rockwell Micro820 is directly targeted at competing with AD and uses the free Connected Components Workbench instead of RSLogix. The B&R stuff is more flexible, even their lowest end compact PLC, and has an inexpensive stepper control option, but requires Automation Studio, which is not free at all.