When electronics release the Magic Smoke, more often than not it’s a fairly sedate event. Something overheats, the packaging gets hot enough to emit that characteristic and unmistakable odor, and wisps of smoke begin to waft up from the defunct component. Then again, sometimes the Magic Smoke is more like the Magic Plasma, as was the case in this absolutely smoked Omron programmable logic controller.
Normally, one tasked with repairing such a thing would just write the unit off and order a replacement. But [Defpom] needed to get the pump controlled by this PLC back online immediately, leading to the somewhat unorthodox repair in the video below. Whatever happened to this poor device happened rapidly and energetically, taking out two of the four relay-controlled outputs. [Defpom]’s initial inspection revealed that the screw terminals for one of the relays no longer existed, one relay enclosure was melted open, its neighbor was partially melted, and a large chunk of the PCB was missing. Cleaning up the damaged relays revealed what the “FR” in “FR4” stands for, as the fiberglass weave of the board was visible after the epoxy partly burned away before self-extinguishing.
With the damaged components removed and the dangerously conductive carbonized sections cut away, [Defpom] looked for ways to make a temporary repair. The PLC’s program was locked, making it impossible to reprogram it to use the unaffected outputs. Instead, he redirected the driver transistor for the missing relay two to the previously unused and still intact relay one, while adding an outboard DIN-mount relay to replace relay three. In theory, that should allow the system to work with its existing program and get the system back online.
Did it work? Sadly, we don’t know, as the video stops before we see the results. But we can’t see a reason for it not to work, at least temporarily while a new PLC is ordered. Of course, the other solution here could have been to replace the PLC with an Arduino, but this seems like the path of least resistance. Which, come to think of it, is probably what caused the damage in the first place.
And now for the obligatory ….He should have just used a 555
Allen Bradley sells pretty cheap smart relays (micro 800 series) and they are much better than Omron Zen.
Omron Zen software hasn’t been updated in years and the limitation in programming them are dumb anyway. I was checking if there were any updates and noticed this:
As of March 31, 2024, the ZEN-Series Controller has been discontinued.
There’s also Siemens Logo!, which costs a lot more than either of those, but is pretty good and versitile.
I’d start with an Arduino board and OpenPLC, but if you need that commercial element, then i’d go with AB.
I just learned how to program Allen Bradley PLCs, it’s actually pretty cool.
The Micro800 is a PLC. That product line is quite a bit more capable than the smart relays I’ve worked with. I think it’s pretty unique among the AB/Rockwell offerings in that there are free programming tools available, which makes sense for a (relatively) low end offering.
I’ve had success with Automation Direct’s CLICK products for simple jobs, speaking of inexpensive products. I believe one of their product lines is based on the aforementioned Arduino if that specifically appeals to you.
Micro 810 is a smart relay, can program that thing right from optional LCD display. 820 and higher are PLCs
Smart relays are PLCs too really, but yes Micro800 series has a wide range of CPUs and addons, so does Logo! now. Still the lower end devices are pretty limited in I/O and features.
i feel like it won’t be ‘fixed’ until they figure out why it popped the first time!
Yeah, that….
A little “root cause” analysis is in order before your fry the remaining contacts.
Having had some experience with similar issues, I can say that in my experience anything energetic enough to smoke the PLC relays like this usually makes itself pretty obvious. Not always, but usually.
Mmm… thermal reluctance anomoly…. :: drools :: /silly
Well, if he is in Germany he has to test only 9999 combinations, the last one is forbidden since a historical movie spawned 9999 memes.