Regarding PLC and i/o modules

[Karan2905]

I have to use more than 40 servo motors and 20+ load cells using PLC. But the problem is that I have to use many I/o modules ( that is costly and hectic). Can I reduce the no of I/o modules by any means or can you suggest something like decentralized control system? Please help me.


In, this picture you can find a tube that I am making. This tube would give me the exact amount of material that I want. It includes 2 servo, 2 stoppers and 1 load cell for measuring the weight. For eg, I want 10 gm sugar. I program the plc in such a way that Stopper 1 that is attached to Servo 1 rotate 90 degrees to uncover the hole, then the sugar falls on the load cell which tells me the weight. When it measures 10 gm on the load cell. Servo 1 comes to its original position with stopper 1 thus stopping the flow of the sugar. Then stopper 2 opens with the help of servo 2 and sugar falls out of the tube.
The problem is that servo is using 2 outputs of PLC. Imagine I have to use 40 such tubes. To accomplish this I have to use many i/0 modules both for load cell and servos. This would increase complexity, cost and reduce the overall capacity of plc to do other tasks very greatly. Also, I want individual load cells and individual servos connected to each tube. Can you suggest me how to reduce the no of i/o modules or you can also suggest a simpler method to measure the weight of a material that is less complex and solves my problem.

 

[PLC]

Ok. I’ll bite
Use servo controllers with a network (Ethernet or ?)
Instead of Plc inputs/outputs

 

[L D[AR2P#0.0]]

You could halve the number of motors by having one motor controlling both stoppers e.g.



0 -80 deg close dose stopper, close feed stopper
90-170 deg open docs stopper, close feed stopper
180-260 deg close dose stopper, close feed stopper
270-350 deg close dose stopper, open feed stopper

 

[Karan2905]

Can you elaborate or explain in detail how can i control 2 stopers with the same motor ?

 

[James Mcquade]

may I suggest that you look at only 1 system and get all the details in place. by that I mean write down the sequence of events in a step by step manner, then add all the I/o.
since you said servos, all servos that I know of requires end of travel limit switches and a home limit switch, direction limit switches. how accurate does the weight need to be? you may need a proportional valve to close the flow of product to get the exact weight. do this first and then see what you need for all the system. you may need more than 1 plc.
james

 

[L D[AR2P#0.0]]

Can you elaborate or explain in detail how can i control 2 stopers with the same motor ?

Connect the two stoppers together phase shifted to get the required action.

 

[JesperMP]

The problem is that servo is using 2 outputs of PLC. Imagine I have to use 40 such tubes. To accomplish this I have to use many i/0 modules both for load cell and servos. This would increase complexity, cost and reduce the overall capacity of plc to do other tasks very greatly.

What you describe appears to be a not particularly complex or large system.
Chose a PLC that can handle the no of I/O and the no of distributed stations. PLCs used to be much more expensive and limited than they are today. There is no reason to try and save a little on the PLC. You will spend much more in the end due to you chosing a too small PLC.

 

[PLCMentor]

Actually I would prefer the servos on a network anyway. You get access to much more information that way. I would also bring the load cells in on a network.