PLCs and Industrial Thread

Still it boggles my mind why anyone would pay such outragous prices for something able to be built for less than 300$ max, is more secure by definition, and you can customize without needing dependency on someone else. I remember reading how the G programming language worked a while back. The whole PLC scene seems like a giant fucking mess to me.
T. neet

Pretty much the same reason Solidworks is still more popular in industry than AutoCAD. Dedicated support is huge in manufacturing where 3 hours of downtime can cost your company $12 million in lost productivity, and you're working with a group of technicians where half of them are smart individuals that could probably learn custom software and the other half are window lickers than know how to fix the mechanical systems but don't know shit about computers past the programs the employer made them learn over the course of a few months.

The window lickers are pretty necessary though since it's extremely hard to get a programmer near a super-hot piece of machinery that's rattling like crazy because something is wrong with it to figure out if they can change the program to fix it or if they have to shut down the equipment entirely for a few hours to cool down (costing a shit ton of money) to hopefully find the problem. A PLC pretty much pays for itself in about a week at most production facilities. At least the micrologix do. Compactlogix might take closer to a month to pay itself off.

The advantage is usability which is important in the industrial field when programmers demand extra to be electromechanical specialists as well (or just flat out refuse to do so).

Also I want to bring up that you'll usually have a compactlogix that communicates/indirectly controls the micrologix via messaging, and a micrologix only costs about $300-$400, which is about what you'd spend bare minimum on an industrial computer anyways after shielding and everything else. Even when you throw in the HMI and software it still pays for itself in about a year at a new facility and stays good for another decade or two.

The OS, schematics, and software are still all proprietary.

visual programming is bad because it makes it impossible to have any sort of abstraction above what they give you, and optimizing for the lowest common denominator isn't an upside. it's not like normal code would be bad either, since it you can still get stick in infinite loops with PLCs and the only reason you get out is because of the watchdog timer

I will make sure to look into that if I ever am in a position to decide on something like that. Sounds like a security risk at best. Backdoor at worst. Gah fuck neet hood. Is there anything like that in other PLC's? I sure hope not.

Well that's the thing about PLCs is you're supposed to run them through devicenet communications or other equivalents (very short very hard-wired system that prevents electrical interference and wireless access). Ethernet is typically the only "out" port where you can access it from outside the PLC, and that's typically suggested to be done as an end point within a closed network for the purpose of communicating with your computer for programming only. PLCs have built in security you can set so folks don't fuck with shit if they're not supposed to, and extension modules like PlantPAX let you set it so you know exactly which operator fucked with what at what time (and even set up what they can fuck with).

Believe it or not, one of the reasons a lot of industrial companies like PLCs is because of their inherent security just through the way they're designed and accessed. Unless some operator decides to take the company laptop home which he broke protocol to connect to the company computer so he could fuck with the program from his house not that I'd ever do that..., the ability to get into the data outside of the facility is extremely limited. Plus the electronic noise from the high voltage a PLC is usually positioned around makes wireless access virtually impossible. Don't gotta worry about blackbox shit like webcams in Windows.

You might enjoy this explanation from wiki: en.wikipedia.org/wiki/DeviceNet

I guess a better way of stating it is unless you know the program, you won't know what changing the bits on the messaging routine will do.

I think something to keep in mind with PLCs is that it's a "universal system" so to speak. The PLC is just sending a voltage to activate an item, and a messaging pulse to tell it which bits to activate. It's then the job of the individual pieces of hardware to interpret that data. A PLC might say turn on bits 5, 7, and 15. The Variable Frequency Drvie that it's connected to then converts that garbled information into settings for how to run the motor it's connected to. This means you can quickly swap out equipment and just change the message being sent, and that people who don't know what your hardware and program are, even if they can access the data somehow, are just gonna get strings of ones and zeros (or integers if working with compactlogix).

Good Morning! Bump.