PLC Stepper Control

[keithkyll]

The motors and drives i was looking at were from Haydon, but that was really only a result of finding them first. Recommendations would be appreciated. Ill probably need like a size 17.

After looking into this more it seems like all i really need to make motion happen are step/direction inputs. As i mentioned before, there is not very much travel involved, and speed is really not an issue, so i dont think i need any acceleration ramps or anything like that. I also found that the S7 has a Pulse output. So here is my question/possible solution, i hope that it is not too misguided. Can i use the pulse output to control all 8 motors? Can this be done using a "multiplexer" as was suggested above? I am also not familiar with that, so some guidance or a recommendation would help. Would this be similar to putting the pulse to 8 relays and then just switching on the relay for whichever motor i want to move?

the way i was thinking, i would need one pulse output going to 8 relays, 8 outputs to control the relays, 8 outputs to control "direction" of the motor. This seems pretty crude to me, but as i mentioned, speed isnt an issue, so whatever i set the frequency at would be fine for all 8 motors and across the entire travel.

am i getting closer?

You are correct - it's as simple as you said. I don't know about the S7. I'm an electronics guy. Try a transistor output module first. Connect the pulse to the common of the 8 transistors. Wire each output to the Clock input of the Stepper Driver module. You might need a module rated for 5 volts, not 24. The limitation will be transistor switching speed. Try it to see how fast you can run before you start missing pulses.
The multiplexer is an IC. I don't know if there's any off-the-shelf types. This is a solid-state version of 8 small relays wired in a 1-of-8 configuration.
Use another set of 8 transistor outputs to drive the direction command.
Use NPN if the module has active low inputs.

If you trust your mechanical operation, encoders may not be needed. "Home" the motors with a home sensor, then use an up/down counter to remember position. Use the same pulse output to run the counter.

Try this with 1 motor, then 2 motors. If you can't get it to work, then buying smart controllers is the way to go.

The accuracy is based on pulses per revolution of the stepper motor, and the pitch of the lead screw. The typical stepper motor will be 200 pulses per revolution, 400 with half stepping. Minimum accuracy is +/- 1 motor step. For 1/16" inch, I would try for 4 times that, or 1/64" per step maximum.

It's easy to undersize steppers. Leave room for size 23.
Use stepper motors with integrated drive electronics. Many have a microstepping option.
Take a serious look at Baldor's website for more info, and a complete range of options.
http://www.baldor.com/pdf/literature/BR1202-C_NextMove.pdf

Let me know if you need more info on the multiplexer idea.

Keith

 

[Orn Jonsson]

Steppers

Look at Automation Direct's Stepper section
Motor -17 $19
Drive - $150
Power supply $100 handles 2 motors

Each motor setup = $220
Micro PLC for control $100

You are looking at $320 minimum for each.

Another good option is using Animatic's servo with onboard drive and controller.

http://www.animatics.com/web/products.html PARKER has those in stock
I have used both of the obove mentioned systems and both work really good. If you need to modify travel distance on a regular basis - use the AD steppers and an HMI

 

[rsdoran]

I did not realize they had these, good option. I do not think he would be able to use a microplc though because he stated 8 axis. I think it would be more appropriate to use a DL205 with 4 H2-CTRIO modules....I did not check to see if the DL06 could use that many cards. This would still provide an inexpensive option overall.
4 power supplies $ 400
8 drives $1200
8 motors $ 152
4 H2-CTRIO $1156
DL205 CPU $ 299 (max price)
DL205 base $ 199 (9 slot)
DirectSoft32 $ 199
Encoders $ 652
I/O cards as needed

The stepper drive manual shows wiring and connecting to a DL plc;
http://web3.automationdirect.com/static/manuals/surestepmanual/surestepmanual.pdf

The counter module manual is here:
http://web3.automationdirect.com/static/manuals/hxctriom/hxctriom.pdf

The DL205 manual; http://web3.automationdirect.com/static/manuals/d2user/d2uservol1.pdf

The manuals offer examples, wiring, and more. It effectively covers connecting encoders too.

My approximate total for the above was $4000 but I did not include any I/O cards.

Personal opinion: I do not believe it can be done as simple as stated in other threads. That option would not offer any actual speed or position control which would be have to be some part of the objective for an application having 8 axis.

If this is a personal out of pocket project you may be able to obtain some parts thru www.plccenter.com at approximately half price.

 

[NorthControl]

Servo

Why not look at servos? I guess this is the expensier way, but i think it's a much more sexy solution!!! The prices are not bad either.

No matter what solution you choose, you need a controller for each motor, right? So any solution will take up space.

I replaced a Parker (Digiplan) system with 2 motors a while ago. That system had 2 motor controllers and 1 Interface (ifc) card. The interface card communicated with the PLC via RS232 ASCII codes. It was really simple, you just send commands with speed, distance etc.) to the card, and the card then tell the motor controllers what to do. Really simple, really.

I replaced that with 2 servo systems, where i did it the same way. Now i just sent the position, the servo controller took care about speed, acceleration, zero run etc.

If you want to have control of where the motors are, i would recommend a set of servo controllers communicating on a fieldbus. Siemens=profibus
Or using stepper motors, use the communication solution! YOU would be in control!
If you use a relay multiplexing solution, the "fake" pulses that might be created can make you loose track of where the motors are... It depends on how the process is, with enough zero-runs or references, it might work though.

Good luck, there is a solution for everything!
Unfortunately, i had to find the solution trying different things. I found that it does not make sense to overtry to make "cheap" solutions, when there are so much plug and play (almost) equipment out there.