Can someone please help me understand this?

[Tinine]

I am self-teaching myself and have an instructor who test me or clarifies things.

Best control systems engineers I have ever known are self-educated.
It's easy but you need to get to a lower level.

Get in to the microcontroller world. Many sheeple will recommend Arduino...Whatever, it's all libraries.

I recommend the RPi Pico (the clones are better) loaded-up with MMBasic
https://geoffg.net/picomite.html

The devices are dirt-cheap and the firmware is free.

IMO, the PLC industry is a HUGE con. People are blowing thousands of bucks when more can be achieved with chump-change.

So here, you get familiar with:
Programming (yeah it's BASIC but it's structured and very powerful)
Digital I/O
Interrupts
PWM
SPI comms
I2C comms
UART comms
Analog to digital
Directly code Modbus RTU
CAN bus
Hook-up a bluetooth module (HC-05 for example)
Hook-up a WiFi module (ESP32 or ESP8266 for example)

Eventually, when you need real-time, deterministic performance, the parallel-processing Parallax Propeller-P2 will blow away anything that you will find discussed on this forum (Beckhoff, Siemens, AB and all the other overhyped garbage)

Get the blinkers off and aim to be more of a creator than a license-paying fool.
Far more lucrative prospects out there.

It really is easy BUT the traditional suppliers don't want you to figure this out.

Craig

 

[drbitboy]

IMO, the PLC industry is a HUGE con. People are blowing thousands of bucks when more can be achieved with chump-change.
...
Get the blinkers off and aim to be more of a creator than a license-paying fool.

Well, IMO this isn't going to generate any responses ...

 

[kckku]

Well, IMO this isn't going to generate any responses ...

Wow.

Companies that employ people generally have standards that need to be followed (programming and hardware). It's not just a free for all where you can go out and buy whatever and then have nobody that can support the system.

This might work for one off or if you are self employed but even your customers will probably want certain hardware and will (should) have some kind of machine specification.

 

[Tinine]

Wow.

Companies that employ people generally have standards that need to be followed (programming and hardware). It's not just a free for all where you can go out and buy whatever and then have nobody that can support the system.

This might work for one off or if you are self employed but even your customers will probably want certain hardware and will (should) have some kind of machine specification.

Really? That's horse doo-doo

Let me know how many examples you want to see:

Since 2000, Every single Corvette chassis is made on my machine. The GM RFQ stipulated "Must utilize AB". I told them that I don't use antiquated overpriced garbage....here's what you get.

Chrysler 300: Same
Boeing: Same
Harley Davidson: Same
Magna Corporation: Same
Lear Seating: Same
Johnson Controls/Hoover: Same
Ford: Same
Navistar: Same

I can list many more...Tenneco Automotive, Arvin Meritor, Faurecia, etc., etc.

Today, I specialise in tossing-out Siemens 840D and Beckhoff CNCs and replacing them with my own so that clients can actually make product.

Craig

 

[cardosocea]

Since 2000, Every single Corvette chassis is made on my machine. The GM RFQ stipulated "Must utilize AB". I told them that I don't use antiquated overpriced garbage....here's what you get.

And in many companies your proposal would be tossed in the bin and the next in line hired to do what the requirements say. Lucky you, but don't think your example makes every single one of us here an idiot.

On the other hand, you'd likely land in trouble with the law if you installed an arduino inside a panel without a silly array of certification and modification work around the platform.

And then there's testing and support of the platform. Yeah, I do think AB is garbage, but PLCs aren't a con, they provide an awful lot to the controls industry and the paradigm that made them exist will still be valid when the PLCs are simply VMs or Docker containers in a large server.

 

[Puddle]

On the other hand, you'd likely land in trouble with the law if you installed an arduino inside a panel without a silly array of certification and modification work around the platform.

Not even that, how many threads do we see here where people are asking about a PLC that's been quietly sat in a panel chugging away for 30+ years and only needs attention when the battery suddenly dies or somebody makes a change?
Reliability is the main selling point of a PLC for me. Surely an automotive production line would be costing the company somewhere in the thousands per hour if it breaks down.

 

[dogleg43]

The test question is poorly worded.
1) Does PC mean personal computer or programmable controller?
2) RS-232 isn’t commonly used anymore?
3) You’re supposed to assume there is a VFD involved?
If possible (or worth the time) I would ask for an adjustment.

 

[cardosocea]

I will be getting a new instructor.

You should take this one to court instead... get your education paid for by a scammer.

 

[dwoodlock]

This is one of those instructor specific questions, where it seems like the correct answer is more closely associated with his personality.

**** question..

 

[harryting]

Really? That's horse doo-doo

...

Today, I specialise in tossing-out Siemens 840D and Beckhoff CNCs and replacing them with my own so that clients can actually make product.

Craig

We had similar discussion many time before here. It's not that one can't program a little chip and replace a million dollar control system it's how that is going to be supported.

conversely, I have rip out many one of a kind system and replaced them with industry standard hardware because no one can support them after the original genius is gone/retired/dead.

ETA: PLC/DCS whatever cost is a drop in the bucket in the scheme of thing depending on the consquence One time we had this system with no label on it broke, one guy in the plant was able to troubleshoot to one single capacitor on the board. We HIRED A PRIVATE PLANE to fly that capacitor over from the midwest to west coast.

 

[arpus4KM]

We had similar discussion many time before here. It's not that one can't program a little chip and replace a million dollar control system it's how that is going to be supported.

conversely, I have rip out many one of a kind system and replaced them with industry standard hardware because no one can support them after the original genius is gone/retired/dead.

ETA: PLC/DCS whatever cost is a drop in the bucket in the scheme of thing depending on the consquence One time we had this system with no label on it broke, one guy in the plant was able to troubleshoot to one single capacitor on the board. We HIRED A PRIVATE PLANE to fly that capacitor over from the midwest to west coast.

Nothing more frustrating for a company than finding out the machine they purchased is unserviceable.

Compiled program only, backups only kept by the creator and when the creator decides it isn't worth it to service or help with it anymore, it becomes a giant brick of a machine because you can't get anything back off the machine. I've been to my fair share of places where the company was purchased or the machine was purchased and they had a power outage or other problem and want to fix/change something... Only to find out that it's basically impossible unless they can find the guy that retired 5 years ago and moved to florida.

 

[arpus4KM]

This is one of those instructor specific questions, where it seems like the correct answer is more closely associated with his personality.

**** question..

This sounds accurate.

 

[jdbrandt]

If a programmable controller controls the operation of
a motor, what connects motor control to the PC?

A) Line voltage
B) I/O device
C) Modem
D) RS232 cable

This was a question on my test. I had B as the answer, but my instructor marked it wrong and selected D) RS232 cable as the correct answer. I am new to all this.

Isn't i/o what connects the controller to the process/motor being controlled?

I am self-teaching myself and have an instructor who test me or clarifies things.

E Any of the above, depending on how you define the terms.