High Speed Counter for PLC

Papabravo

Joined Feb 24, 2006
13,759
How to design a high Speed counter for PLC ?(I'm relatively new to PLC's?)
Thanks in Advance.
It is pretty easy to tell you how to get started. You must define your requirements
I can give you a list to guide in this process if that would be of interest.
Alternatively, you can just spend a few minutes to write, and tell us what you should have told us in the first place.
Did you think we were mind readers with powers of precognition?
 

Thread Starter

Mary Theresa Dominic

Joined May 28, 2020
2
Thanks for your reply.
Sorry this is my first time posting, and first time using this forum!
I just began my career as a hardware design engineer and my first task is to implement high speed counter for PLC (RX632N- Renesas 32 bit micro controller which as sensors as its input module ). I have the basic idea of PLC and all its block. So I need help on how to get started in high speed counter ,how does it work and what are its blocks and how do i interface it.

Any help would be greatly appreciated.
 

Papabravo

Joined Feb 24, 2006
13,759
Thanks for your reply.
Sorry this is my first time posting, and first time using this forum!
I just began my career as a hardware design engineer and my first task is to implement high speed counter for PLC (RX632N- Renesas 32 bit micro controller which as sensors as its input module ). I have the basic idea of PLC and all its block. So I need help on how to get started in high speed counter ,how does it work and what are its blocks and how do i interface it.

Any help would be greatly appreciated.
Have you been given any requirements or objectives for this project?
If so it would help to know what they are. If not I have some questions
  1. What will you be counting?
  2. How fast is fast, or what will be the maximum arrival rate of events that you need to count?
  3. Will the counter count up or down or both?
  4. Is this a decimal counter or a binary counter?
  5. What is the range of values it can accommodate?
  6. Will you be implementing this counter with an ASIC or FPGA?
  7. What happens when the counter gets to the maximum or minimum value?
  8. What outputs will you require?
  9. Will you need to preload the counter to an arbitrary value?
  10. Are there similar designs that you can study and ask questions about?
That should get you started.

If you have never seen anything like this, here is a datasheet for a counter building block. It is 4 bits wide, but can be cascaded with identical parts to make a counter of ANY length

https://www.ti.com/lit/ds/symlink/cd54hc163.pdf?ts=1590675439414

If nothing else it will indicate one or more desirable features of any counter.
 

MaxHeadRoom

Joined Jul 18, 2013
20,726
PLC's in general are not that good for high speed events, although the term high speed is relative, this is due to the scan and data update time.
As a rule, for high speed events in a PLC, a specialized board is used to accomplish this.
Max.
 

Papabravo

Joined Feb 24, 2006
13,759
PLC's in general are not that good for high speed events, although the term high speed is relative, this is due to the scan and data update time.
As a rule, for high speed events in a PLC, a specialized board is used to accomplish this.
Max.
Excellent point, which is why I am curious to explore the requirements and expectations for this project. I realize that disclosure of company confidential information may be a sensitive issue for a new engineer which is why we need to keep this as abstract as possible for the time being.
 

MaxHeadRoom

Joined Jul 18, 2013
20,726
I guess I did not read thoroughly enough as it seems the OP, although mentioning PLC, is actually using a high end Microprocessor!
Max.
 

Papabravo

Joined Feb 24, 2006
13,759
I guess I did not read thoroughly enough as it seems the OP, although mentioning PLC, is actually using a high end Microprocessor!
Max.
It is often the case, as when I worked at Allen-Bradley, that PLCs are implemented with high end microprocessors. In that era (ca. 1992) it was the 80186 possibly in a dual arrangement. One was the IO Scanner and the other was solving the ladder, but I'm not 100% sure about that. They were using μC/OS from Labrosse.
 

MaxHeadRoom

Joined Jul 18, 2013
20,726
It is not so much the processor as the method used in just about all the versions I have used and that is they run a scan through the ladder, rung by rung, and record the output status etc, at the end of the scan, the data table is updated and the next scan continues, this is the reason for such things as a PID loop motor controller etc, having their own hi-speed card in a slot.
I suspect the OP is using 'PLC' in a wider sense.
Max..
 

Papabravo

Joined Feb 24, 2006
13,759
It is not so much the processor as the method used in just about all the versions I have used and that is they run a scan through the ladder, rung by rung, and record the output status etc, at the end of the scan, the data table is updated and the next scan continues, this is the reason for such things as a PID loop motor controller etc, having their own hi-speed card in a slot.
I suspect the OP is using 'PLC' in a wider sense.
Max..
Sure, but the TS (Thread Starter) has not given us much in the way of information. Maybe she will, and maybe not.
 
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