I spend a lot of my time at a desk in a parts distribution center here in Monterrey. We do a ton of business in industrial automation parts, specifically PLCs. My job? Figuring out how to get a customer the right module, sometimes within hours, not days. So when I hear arguments over 'Siemens vs. Allen-Bradley' that are just about market share numbers, I kinda roll my eyes. Market share tells you who sold the most five years ago. It doesn't tell you who can get you a replacement CPU by Tuesday morning.
Here are the real questions I get from engineers and plant managers on the ground, not the sales guys.
The common line is that Allen-Bradley (Rockwell) has a higher market share in Mexico, especially in the automotive and packaging sectors. That was accurate as of 2020. It still holds true in a lot of big, established plants. They've got a massive installed base, so a lot of greenfield projects still spec Rockwell because the maintenance team already knows it.
But—and this is a big 'but'—Siemens has been making a huge push. I've seen their presence in the food & beverage and chemical sectors grow noticeably in the last three years. Their TIAPortal software is also a game-changer for younger engineers who grew up with integrated development environments. So market share is shifting, but it's a slow boat, not a speedboat. The 'winner' depends entirely on the specific industry vertical.
Yeah, I get this all the time. This was accurate as of mid-2024, but TIA Portal updates change things fast, so verify current best practices. The short answer is: the logic is the same. A PID loop is a PID loop. The hardware addressing is where the difference bites you.
Key differences:
Can you transition? Yes. I know a guy who converted a whole plant from AB to Siemens in 2023. It was a six-month headache with a specialized integrator. They didn't rewrite the logic; they rewrote the addressing. The code functions the same, but looks completely different. Bottom line: if you have a team of 10 AB programmers, retraining them is a bigger cost than the hardware.
I've seen this one cause a panic. The short, safe answer: No. Not for the CPU module itself.
You use a 24V DC power supply for the Siemens S7-1200 or S7-1500 CPU. A 36V battery charger is for a forklift or a specific backup system, not the PLC logic rack. If the power cuts out, you need a proper 24V UPS battery backup (like from Phoenix Contact or Weidmüller) designed for the DC bus, not a charger for a golf cart battery. That 36V could fry the input module something horrible. I saw a guy try it once just to keep the program running. It didn't end well. So glad I wasn't on that call.
For the HMI or a remote I/O panel? Maybe. But you'd better check the exact input voltage specs on the nameplate. Even on those, I wouldn't risk a universal charger. Use the right tool for the job.
Mixed feelings on this one. Part of me thinks a good two-year technical program is fantastic for the fundamentals—relay logic, ladder logic basics, safety circuits. You learn the theory. The other part of me knows that you learn the real skills on the job, usually when you're panic-troubleshooting a fault at 3 AM.
What a school should teach (but often doesn't):
If a school focuses only on 'coding' a PLC in ladder logic, they're missing the point. The best programmer I ever worked with was a mechanic first. In my role coordinating emergency service for a construction company, I don't care if a guy can write a 500-rung program in 30 minutes. I need him to find which rung broke in 5.
This is a weird crossover question I get from new automation engineers. You're building a machine vision system, using an Nvidia GPU for AI inference, and you want to tie that output to a Siemens PLC via a digital output or a TCP/IP message.
The Nvidia Control Panel is for display settings (resolution, refresh rate, surround sound). It won't help you here. You need the Nvidia DeepStream SDK or a similar software library to write the application that communicates with the PLC.
What you'd actually do:
It's a common confusion. You use the GPU for processing, not for I/O. I've seen engineers lose a whole day trying to find a 'PLC mode' in the Nvidia driver settings. There isn't one.
I get this from people starting a small project or a repair. They're worried their $300 order will be ignored.
When I was starting out as a maintenance tech, the vendors who treated my $200 orders seriously are the ones I still use for $20,000 orders. Small doesn't mean unimportant—it means potential.
Will a big, massive distributor ignore you? Maybe. But many specialized distributors (like the one I work for) are built to handle this. We have a specific counter-sales team for small orders. The trick is to find a distributor that focuses on service and stock availability, not just massive OEM contracts. Look for ones that have an online store with real-time stock for Siemens parts. If they can sell you ONE fuse, they'll usually sell you ONE PLC. It's the guys who only want to quote on full panel builds that are a pain.
Small orders are how we build relationships. Big clients start small.