I Wasted $1,200 on a Mitsubishi PLC Setup (And How You Can Avoid My Mistakes)

I've been handling Mitsubishi PLC orders and programming for about 7 years now. I've personally made (and documented) 14 significant mistakes, totaling roughly $4,800 in wasted budget. My biggest single error—a $1,200 blunder—happened because I assumed my setup was standard. It wasn't. Now I maintain our team's checklist to prevent others from repeating my errors.

So, you're looking into Mitsubishi PLCs. Maybe you're trying to decide between an FX5U and a Q series. Maybe you're trying to figure out whether online training is worth it. Or maybe you're wondering how to even test basic components like a 9V battery with a multimeter because your control panel is suddenly dead.

Here's the thing: there's no single 'right' answer for most of these questions. It depends on your application, your team's experience, and your budget. So instead of giving you one generic recommendation, I'll walk through the most common scenarios I've seen, point out where I screwed up, and help you figure out which bucket you fall into.

Let's get into it.

Scenario A: You're a Beginner Picking Your First Mitsubishi PLC

If you're just starting out with PLCs, the conventional wisdom is to get the cheapest, simplest model. Usually, that points you toward the Mitsubishi FX series (like the FX3U or even the older FX2N). And honestly, for learning, that's not a bad start.

What I initially did wrong: I bought a used FX2N off a forum because it was $100. I thought, 'It's basically the same as the newer ones, just older.'

Everything I'd read about PLCs said hardware compatibility is backward. In practice, I found the opposite—at least for Mitsubishi. The FX2N uses older programming software (GX Developer) that's clunky and doesn't support some of the modern instructions I needed. Plus, finding replacement parts was a nightmare when a relay died. I ended up spending $300 on a used replacement plus a lot of wasted time learning software I'd never use in a real job.

My actual recommendation for beginners (2025):

• Get an FX5U if you can afford it ($300-500 new). It uses GX Works3, which is modern and well-documented. The built-in Ethernet and USB ports make connecting to a control panel a breeze.
• If your budget is under $200, look for a used FX3U. It still uses the older GX Developer software, but there are way more tutorials online for it than the FX2N. And it's still actively used in small machines.
• Don't buy an FX2N unless you literally have no other option and a lot of patience.

The insider secret: What most people don't realize is that Mitsubishi's 'entry-level' PLCs (FX5U) have eliminated a lot of the frustrations you'd expect from a budget model—like needing external converters for Ethernet. It's not a compromise; it's actually a solid learning tool.

Scenario B: You Need a High-Performance System for a Machine

This is where most people jump straight to the Q series. It's powerful, modular, and the industry standard for mid-to-large machines. But here's the mistake I made in 2022.

I was programming a packaging line that needed to handle 120 cycles per minute. I specified a Q06UDEHCPU, thinking 'more power is better.' The system worked, but I didn't account for the complexity of wiring the I/O modules correctly with the control panel. I assumed a standard 24V power supply would work. It didn't. The surge protector I'd installed (a cheap one I had lying around) couldn't handle the inrush current from the Q series base unit when all the outputs fired simultaneously.

The result: $600 in damaged modules, a 3-day delay, and a very angry production manager.

Here's something vendors won't tell you: the Q series is fantastic, but it demands a clean, stable power supply. A 'standard' surge protector for a 20A circuit won't cut it. You need something rated for industrial use.

What I do now: I test the power supply with a multimeter before even mounting the base unit. I specifically check for voltage drop under load. If I see anything more than a 2% drop from 24V, I know I need a better power supply or a higher-rated surge protector. Speaking of which...

A Quick Note on Power: What Size Surge Protector for a 200 Amp Service Panel?

This is one of those 'take this with a grain of salt' situations. If your entire control panel is fed from a 200 amp service, you're not protecting the whole panel with one little power strip. You need a Type 1 or Type 2 surge protective device (SPD) installed at the main panel. For the PLC and sensitive electronics inside your control cabinet, you need a secondary SPD rated for 120/240V, usually in the 20-50kA range.

Don't hold me to this, but I've found a 60kA SPD at the sub-panel works well for most Mitsubishi PLC setups. Verify current requirements with your local electrician. I've seen too many PLC failures blamed on 'bad wiring' when it was actually just a surge that the protector wasn't rated for.

Scenario C: You're Trying to Learn PLC Programming Online

This is where my biggest mistake happened. In Q1 2024, I decided to save $800 by skipping a formal training course. I figured, 'I've been doing this for years. I can just watch YouTube videos and figure out the newer GX Works3 software on my own.'

I knew I should commit to a structured program, but thought, 'What are the odds I'll get stuck on something stupid?' Well, the odds caught up with me. I spent 6 weeks trying to understand how to correctly write a structured text (ST) program for a PID loop on an L series CPU. A 6-week delay cost my company roughly $2,000 in lost production time.

I ended up buying an official Mitsubishi PLC online training course (about $600 from a local distributor). I learned the proper method in 2 days.

The lesson: Don't be cheap with your education. Online training for PLCs is not a scam—it's an investment in not making my mistakes.

Is mitsubishi plc online training worth it?

Yes, but only if you get it from an authorized source. There are a lot of $50 courses on random platforms that promise to teach you 'everything.' They're rarely comprehensive. Look for training that specifically covers software simulation, hardware configuration, and troubleshooting. The best training I've seen uses actual hardware simulation where you can break things virtually.

My recommendation for beginners (2025): Spend $200-600 on a course from a Mitsubishi distributor or an accredited training center. It will include a PLC simulator license, which you can use to practice. Then, use free resources (YouTube, forums) for specific questions. I'm not 100% sure, but I think the average person saves about 4 weeks of frustration by doing this.

Scenario D: You're Troubleshooting a Dead Control Panel

Your machine stopped. The control panel is dark. What do you do?

First, check the power supply. I can't tell you how many times I've seen someone panic and order a $1,000 PLC replacement when the problem was a $20 blown fuse or a dead 9V backup battery on the PLC's real-time clock.

How to test a 9V battery with a multimeter:

1. Set your multimeter to DC voltage (20V range).
2. Touch the red probe to the positive terminal (+) and the black probe to the negative terminal (-).
3. A healthy 9V battery should read 9.0V or higher. If it's below 8.2V, it's weak and should be replaced. If it's 0V, the battery is dead.

The catch: This was true 10 years ago when most PLCs used simple backup batteries. Today, many Mitsubishi FX5U units use supercapacitors that hold a charge for a few minutes, not a coin cell. But many older machines still use the 9V. So before you assume something expensive is broken, test the cheap stuff first.

How to Know Which Scenario You're In

If you're asking yourself, 'Which one applies to me?', here's my simple decision tree:

• Are you new to PLCs? → You're in Scenario A. Prioritize a modern FX5U and get proper training.
• Are you building a complex machine for production? → You're in Scenario B. Go with a Q series, but spend the extra $100 on a good power supply and surge protector.
• Are you trying to self-learn? → You're in Scenario C. Don't be me. Pay for the training.
• Is your panel dead? → You're in Scenario D. Check the battery and fuse first. 90% of the time, it's one of those.

I've made these mistakes so you don't have to. It's basically a trade-off between being smart with your time and money vs. being lazy and throwing cash at problems. Honestl., the industry is moving faster than ever. The guys who invest in proper training and proper hardware are the ones who stay ahead.

Good luck. And if you have a specific question, drop it in the search bar. I probably have a post about the mistake I made with it.