Need help - motor control

Hi everyone, I'm a beginner and trying to come up with a simple motor control system. I'm hoping anyone can advice me on what hardware and/or software is needed. Please keep in mind that this is system is built from scratch.

(1) User uses joystick, send signals to PC.
(2) PC running PLC receives input, and sends signals to motor.
(3) Motor runs.

I would appreciate any help on how to get started, prefably the simpliest setup for now. I hope I got the concept right Please feel free to advice. Thank you!

When you say PC, think expensive.


As far as a PLC goes, you could do it relatively inexpensive with any number of PLC's, such as :

Entertron
Keyance
General Electric
Automation Direct
Allen Bradley
etc.

As far as the joystick goes, why a joystick.

You only need faster and slower.

Please provide more info!

CWLeong said:

Hi everyone, I'm a beginner and trying to come up with a simple motor control system. I'm hoping anyone can advice me on what hardware and/or software is needed. Please keep in mind that this is system is built from scratch.

(1) User uses joystick, send signals to PC.
(2) PC running PLC receives input, and sends signals to motor.
(3) Motor runs.

I would appreciate any help on how to get started, prefably the simpliest setup for now. I hope I got the concept right Please feel free to advice. Thank you!

Click to expand...

For the application you describe, you don't need a PC. You could just get a PLC with pulse-train outputs (to drive a stepper motor) or analog outputs (to control the speed of an AC or DC motor drive). Look in any electronics supply catalog and you'll find a selection of joysticks with discrete outputs that could be connected directly to a PLC's inputs.

Post more information and we can provide more help.

The simplest system would be to wire the joystick directly to the drive input. Most Joy Sticks have a center pin that goes to the drive's terminal strip 0 Volt pin. You connect the + and - terminal voltages, usually 10 vdc to the joy stick so when you move the stick in the desired position, the object is moved that way. If your joystick is backwards to start you can just swap the wires on the + and - terminals to correct.

If you are for sure going to use a PLC/PC system, you need an analog input module in the PLC and an analog output module by the drive. You might need to have a seperate power supply to power the joystick depending on the distance between it and the PLC/PC and Drive.

CWLeong said:

...prefably the simpliest setup for now...

Click to expand...

A down-to-earth motor control makes no use of a PC and a PLC.

Is the motor speed supposed to increase/decrease or rotate CW/CCW, or a combination of both, according to the joystick's position?

Do you really need the PC? I'm sure you can use a joystick's internal circuitry without one. In most cases you could hook it up directly to a motor controller board.

Like the other posts say, a bit more info could be helpful...

Without knowing more about your project, it is hard to be specific. If you must use a PLC, you have several options. You also have several options if you have a drive with or without a PLC as mentioned above.

Having said that, I recently purchased a cheap little DC motor control unit (DCPWM7) for a project I am working on as a hobby around the house (that I've asked for help here several times as well)

http://www.chapp.com/

It has three inputs that will give you 7 different speeds selectable by the various combinations of inputs. It also has a 'teach' button so you can set the speeds to whatever you choose.

As I said, I don't have any idea what you are trying to control, but this looks like it will work for my little project. (if I ever get it done, I'll make sure to post it here and give you guys credit)

Thank you all for the replies. Certain I have learnt a lot and have a long way to go I apologize for not having enough info for the time being, but what I intend to do is similar to cntrlfrk's project. I'm leaning more towards on T100MD+ (http://www.tri-plc.com/t100md.htm) since it's the only source in my region. I will definitely need a PC for this.

I intend to control 2 DC motors in realtime. Assume using T100MD+, am I right in only needing a input device, PC and the motors? I'm unclear on the motor side - does the T100MD just generate signals or does it also supply voltage for the motors? If it doesn't, how is the hardware set up supposed to be like?

Please bear with me I hope to provide a clearly picture after I understand more.

CWLeong said:

I intend to control 2 DC motors in realtime. Assume using T100MD+, am I right in only needing a input device, PC and the motors? I'm unclear on the motor side - does the T100MD just generate signals or does it also supply voltage for the motors?

Click to expand...

Yes, even the basic T100MD888+ can drive two 24Vdc-10A motors directly. Using these PWM outputs you are capable of controlling the motor's speed. Changing rotation is another issue, but it can be done by adding a DPDT relay (controlled by an extra T100MD output) to invert the motor's connections.

You just have to 'tell' this PLC card when & how fast (& maybe in which direction) you want each motor to run: Feed it an analog signal or use digital inputs.

CWLeong said:

Hre and/or software i everyone, I'm a beginner and trying to come up with a simple motor control system.

I would appreciate any help on how to get started, prefably the simpliest setup for now. I hope I got the concept right Please feel free to advice. Thank you!

Click to expand...

You shouldn't need a PLC or PC to do this. You should be able to run the joy stick references directly into the motion controller. If you cannot meet your specificaitons then look at this

http://www.deltacompsys.com/products/motion/rmc70/index.php

This controller can run standalone. It has a special PID that works best for following analog references and it has the ability to filter the analog input ( four pole Butterworth filter ) so the motor does not jump around responding to noise or quantizing errors. If necesary you can also use a formula to make the joystick input non-linear so the gain is much lower when around zero and higher when the required velocity is closer to the maximum. This would be the fastest way to get the job done.

If u r not using a plc better go for hard ware control with one inverter drive.connect ur joystick to the inverter directly(0-10V) controlthe speed of the motor by varying the pot in the joy stick.Its simple

or if u want to go with the plc u need one analog input for reading the joystick signal and one analog output to drive the motor.

shanmu_gam said:

If u r not using a plc better go for hard ware control with one inverter drive.connect ur joystick to the inverter directly(0-10V) controlthe speed of the motor by varying the pot in the joy stick.Its simple

or if u want to go with the plc u need one analog input for reading the joystick signal and one analog output to drive the motor.

Click to expand...

Did you notice that he said 2 DC drives? How do you use an inverter with DC drives?

If I am not mistaken a joystick, that has potentiometers, would need at least 2 analog inputs...depending on the situation. In this case there are 2 motors so to forward and reverse both I would think it may need at least 2.

Please explain how it is simple.

rsdoran said:

If I am not mistaken a joystick, that has potentiometers, would need at least 2 analog inputs...depending on the situation. In this case there are 2 motors so to forward and reverse both I would think it may need at least 2.

Please explain how it is simple.

Click to expand...

The hardwired solution may work if you use some diodes to create the dead zone but diodes leak even when there isn;t .6 volts across them. One can always design a circuit to create this dead zone. What if there is a bias to the drive input of a couple millivolts? Then the motors will still drift.

This part is simple in a real motion controller where mathematical forumulas can be used to map voltage to from the joystick to a velocity commad to the motors. One can use a joystick that has +/-10 volts applied to it so it can return +/-10 volts too. One can 'bias' a 0 to 10 volt joystick so that 5 volts equates to 0 speed. -5 equates to full reverse and +10v is full speed forwards. Usually a manual analog reference ( joystick ) requires a small dead zone too so there is a small area in the center of travel where the output will be 0. This allows on to stop the motor easier. Otherwise you must move the joystick to exactly the right position to get the motor to stop which isn't really practical. The joystick should have a spring return to center so that if the operator lets go the spring pushes the joystick back to the dead zone where the output is 0 velocity.

Actually, the best way is not to use velocity commands but rather integrate joystick output to yield positions. If something goes wrong you just stop integrating or adding to the command position so the motor stays still and holds the current position.

Sounds like a senario I had with an Extrusion press years ago. I had an industrial joystick that had a multiwound pot. ohm The pot was set up for spring return with 2 micro switches between the dead zone . If I remember correctly, the pot was 2500 ohms wire for +1225 ohms to forward stroke and -1225 to reverse stroke. The other 50 ohms were split in the dead zone between the limit switches . The forward stroke limit switch would activate channel 1 with +0-1225 ohm going to the analog card on chan.1 and the reverse stroke would activate the rev limit switch and activating chan.2 and sending -1225 -0 ohms to chan 2 anolog card. The 50 ohms were split in the dead zone -0-25 and + 25-0. or vice versa. so long as the switches were in the center the dead zone would not allow the press to move forward nor backward.
This process might work with the motor drive controller with the use of relays to control seperate drive motors or both with some fancy ladder logic. Just a thought.

rsdoran in part said:

Did you notice that he said 2 DC drives? How do you use an inverter with DC drives?

AND

Please explain how it is simple.

Click to expand...

I think that he is using a Wye-Delta transformer between the drive and the motors.

I think that he just needs to only hook two of the leads up for the motor, being syre to use white tape for the third lead to be sure that it is not used, unless it is a government project.

For government projects, it is required to use "RED TAPE".

sorry, i just hadda say it.

I don't think he is versed on resident smoke and flux capacitors, so we'll leave those for his next thread!!!

Hope things are going well down there Ron.

We'd be happy to send some of this cold and rain if you want it!

Hey I mean he is going to control the induction motor with the help of joy stick