Low Cost PLC systems

Hello All

I am trying to find a low cost PLC system that has a minimum of 8 high speed outputs for stepper motor control, can accommodate Servo control, and analog I/0.

I have looked into some Micro PLC systems and found they do not have enough high speed outputs.

I am also hopping for a low cost solution because I will be installing up to 20 PLC's at a time and networking them together with a host, and HMI's for each Unit.

Any recommendations will be greatly appreciated.

Allan,

How fast do your outputs need to be in either millisecond response or Hz / KHz?

Would it be safe to say that you would require 8 analog outputs / per system, one for each output?

In the curent micro procesor based system the steppers are running at about 400hz, so 10Khz is lots. As for my analog I/O, I dont need a high speed responce. The change in the running speedds happens gradualy

I should also mention that space is a major consideration in this system. I dont have a lot of room to play with in side each machine.

question........

How critical is the duty cycle of the PWM ? What is the current requirements of your stepper motor (control signal) ? Also how fast of a response time do the PWM outputs have to be ?

Dave

At the moment the curent system is runing at about 120 pulses per minuit.

Allan, Stephen cant say this but I can, he is a representative for this company: http://www.entertron.com You may want to Private message or email him to see what he can offer. Sounds like a system that he could easily accomodate.

Another option is to look at: http://www.automationdirect.com They are the most competitively priced and may offer the options you need.

There is also:
http://www.unitronics.com

One other option I am very familiar with is: http://www.heapg.com This is Horner Electric which for many years has been a 3rd party vendor for GE. They offer a line, OCS, that is a PLC and HMI all in one. The CScape software is free and programs both the PLC and HMI, the instructions are similar to GE Fanuc set. They use a CAN network that allows programming any unit on the network, they can also use Devicenet. They offer stackable or din rail mountable I/O that includes High Speed counters and a Stepper Indexer module. Their prices are also competitive and they are compact.

Allan,

What is your available space to work with?

Also, you mentioned inexpensive...what is your price range that you can work with?

There was a typo in the spelling that Ron provided you of our company was incorrect...it should be www.entertron.com

We might have an option, but it will depend on the answers you provide to the questions above.

In the original post, Allan specified that the controller

can accommodate Servo control,

Click to expand...

None of the brands or models so far proposed have native servo control capability (as far as I know). I think you'll find that's out of reach of most budget-priced and micro-sized controllers, especially if you want to do coordinated axis motion.

What sort of servo functions are you looking for ? How many axes ? Can you network servocontrollers on serial or DeviceNet or SERCOS networks ?

I only need one axis of control on the servos.

I want to stay away from serial communications, and go towards a field bus type system. Ideally I would love Ethernet, but there is to much wiring.

I have already found I can not use the "Micro" PLC systems.
My concern is that my next step is going to SLC500 type system(better option as far as I am concerned). I realy am not sure what my budget is at the moment.

I just know what I need to control, and they want to go to a PLC based system, and away from the micro processor system they developed.

I am thinking they were looking at about 2 grand per controller,that can do:
- 6 stepper motors
- Communicate to servo controllers using an open protocol
- Communicate to an HMI using an open protocol
- use Analog I/O to control DC drives
- have a base of 32 I/0
- Communicate to a Master, but also be able to be a stand alone unit in case of an emergency

I have the different reps coming in from AB, Omron, Modicon, and even unitronics. However I doubt the unitronics can handle this.

Just trying to be better informed, as typically I have worked where the customer has specified what vendor I use.

Now that I am working for an OEM, I will be trying to figure out what we use from this point forward.

I am very happy with the help you gentlemen have been able to provide. Thanks

Looks like a lot to do for 2 grand. I think that Automationdirect's stuff can do it if the servo talks MODBUS RTU. But it may be even difficult to put together an Automationdirect system to do all that for 2 grand.
But...maybe those manufacturer rep's will come in with some steep discounts...

Try these guys, Triangle Research Inc.
http://www.tri-plc.com/t100md.htm

They make low cost PLC systems with A/D, D/A, PWM, Stepper outputs, Servo control, and Modbus RTU, ASCII. As well as a bunch of other neat tricks.

I have used them extensively in harsh environments without problems.

Willpower100

I would consider compact logix with DeviceNet. Your HMI and your servo drive could be on the DeviceNet network. I havent looked in to high speed outputs for the compact logix line, but im sure your AB guy will be more than happy to do it.

With compact logix you have a choice of using either Logix 5000 (with the compact logix processors) or you can goto a mircologix processor and use Logix 500. I havent done the second route so I cant help you much there.

I am sure your AB rep could put together a nice little compact logix package for you though, and it would be more compact (no pun intended) than a SLC500.

Good luck!

Since you have all those vendors coming contact Horner...ie Paul Horner and see what he has to say, wont hurt.

Is low cost REALLY your first priority ?

With all that you specify (bus networking, stepper motor control, analog i/o), I guess that the system that you are going to control is not so simple after all.

Methinks that low cost is a priority, but not the first one.
One thing that you havent stated is the amount of processing power and memory of the controller (OK its difficult to line out beforehand). It would be sad if you handicapped the final design by letting it run on an "ant brain".

As this is probably the first of a kind for you, it would be much smarter to select a slightly larger model than first intended.
To be too pennywise in the beginning, can be very expensive in the long run.

A lot of VF drives and Servo Drive inverters have built in PLCs.
One example I can think of is the SEW range, which has an inbuilt Siemens Logo PLC. This may be a lower cost option if you have to buy VF drives anyway. I don't know about stepper motor drives though.

Doug