Last question ever

Explain one example of each of the three types of communication media (e.g. twisted pair, coaxial etc) would be selected for a specific programmable controller application.
What type of communication media would you select for the following?
(Justify your answer)

UNITARY PLC when used in a 2 way traffic light system:
MODULAR PLC when used on a traffic light system for a town:
RACK MOUNTED when used in traffic light system for underground railway:

This is actually the last question of my assignment and the one which i am most struggling with. Just need to know bullet points really.

before you say ****, This is a course within a course so I will not be stealing your job as I don't have interest in PLCs. and the only thing i know about PLCs are binary and that. i can't even code a program or even a shadow detector so please don't worry I wont take your job...

As I said it is only one question I've spent HOURS on the other one which i have just finished and i just need little information. BTW i do not know what unitary modular and rack mounted are but i can write stories as usual. the only thing i do know is the price and that rack mounted is the best one and i don't even know why.

At least i'm trying to put in effort as i am sharing my story with you and hopefully you understand that i need help for the last bit as i have been trying to find information about this hours without success, and after this i have more to do but not in PLC.

What even is communication media examples?!?!?!?!?!?/

Mark Snodgrass said:

google!!!!!
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I beg you tell me what to google or what website to go, to find this specific answer .......

Just coz i didn't make it look like, 'i was just wondering'

Ok i finished 2 of them but i just need to know which communication media(transmission) is required for the traffic light in town ( smart traffic lights) with a modular PLC.

Alright, you're on the back of a boat. Best place, really.

As you've seen this horrible question from the HNCs shows up again and again, with these poor students claiming that their teacher is worthless and the information just isn't available on the Internet. Some of them say they just can't begin to possibly understand such a complex topic, but your "negging" approach in saying you're not even interested in the topic is unusual.

I don't even feel like researching the history of the question on the Forum.

So let's just talk about the basic architecture of Programmable Logic Controllers for a while.

As the sig line from my friend Bernie Carlton goes: "Controlling outputs is the PLC's way of getting its inputs to change."

Programmable controllers take various electrical inputs from sensors, run a repeatable logic program, and send output signals to devices like lights, valves, and motors. Then they do it all again.

So when you're an industrial designer building the physical parts for a logic controller, the question of how many and what type of input and output circuits is very important.

Very small logic controllers will have a fixed number of inputs and outputs, all built into a single enclosure.

Middle-sized logic controllers will have expansion input and output circuits. They usually plug onto the base unit in modular sets of 8 or 16 or 32 points.

Large scale logic controllers will have a wide variety of input and output circuits, so they'll have a chassis, or "rack" of a fixed size, into which you can plug modules with 8 or 16 or 32 points of Input and Output circuits.

There are of course products that blur the lines between these categories, but they're a pretty good way to describe the general architecture of different logic controller products.

finished phew............... i used serial as it makes it smart and you can deal with more stuff n and it also has sensors. thanks for the help

The HNC uses these examples because they figure that most folks have pondered how traffic lights are controlled.

A simple two-way light wouldn't need to communicate between multiple stations at all. You'd have a control box, and lights on a pole, and ordinary discrete wires between them, so that one wire would provide power to one lightbulb.

A traffic light system for a town might need to co-ordinate between control boxes over medium distances, right ? If you want all the North/South roads to run at the same time, then halt, then run the East/West roads, you'll need some way to co-ordinate between the signals. Just running everything on timers would never work; the timers would get out of sync and there would be gridlock. And you couldn't change the system to account for events like emergency stoppages, or a train running through town.

The HNC talks about underground railways to get you thinking about long-distance communication networks. Stations on an underground railway are going to be further from one another than control boxes in adjacent blocks of a town.

Ken Roach said:

The HNC uses these examples because they figure that most folks have pondered how traffic lights are controlled.

A simple two-way light wouldn't need to communicate between multiple stations at all. You'd have a control box, and lights on a pole, and ordinary discrete wires between them, so that one wire would provide power to one lightbulb.

A traffic light system for a town might need to co-ordinate between control boxes over medium distances, right ? If you want all the North/South roads to run at the same time, then halt, then run the East/West roads, you'll need some way to co-ordinate between the signals. Just running everything on timers would never work; the timers would get out of sync and there would be gridlock. And you couldn't change the system to account for events like emergency stoppages, or a train running through town.

The HNC talks about underground railways to get you thinking about long-distance communication networks. Stations on an underground railway are going to be further from one another than control boxes in adjacent blocks of a town.

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fiber optic obviously for the underground railways. at least i understand more than i did before

You'll see that your actual question asks "which of the three types of media" you would use, then gives just two types of media examples (twisted-pair and co-axial).

I suppose "serial" was the third one.

Twenty years ago I couldn't tell a serial port from a screwdriver. I asked an expert to explain how serial ports worked, since I didn't understand anything about how the pulses of electricity on the Tx and the Rx ports were translated into bytes in the controller. I didn't know what the "RS" meant in "RS-232" or even what an EIA standard was.

He sat me down in front of a whiteboard and started drawing pulses, and counting bits, and explaining start/stop and parity and error checking. I was fascinated.

Decades later, serial analysis and the ability to jump into control systems communication at the lowest levels has been a crucial part of my skillset. I travel around the world designing, commissioning, and fixing huge high-tech machines that do some of the world's most advanced manufacturing processes. It pays well, and I get a challenging work environment every day.

When you find something like that in your education that really interests you, grab onto it and learn as much as you can. It doesn't matter if it's an aspect of math, or engineering, or law, or literature. When you find something that resonates with you, grab on and drink it up in bucketfuls.

I sympathize with the original poster. You've heard the expression "There's no such thing as a stupid question"? Well, this instructor proves that expression is wrong!

Any of the media types could be used for any of those systems.

Any of the media types could be used for any of those systems.

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While that is true, it does not make it right. I can use my iPAD to put a nail in my wall to put up a picture.

The approach mr. Roach takes is plenty to get to an meaningful answer. I appreciate the "teacher" in you Ken, always taking the time to not only giving valuable pointers to get to an answer but also providing some "attitude adjustment". Thanks!