omron

3 Articles

Quick And Very Dirty Repair Gets Smoked PLC Back In The Game

November 21, 2024 by 11 Comments

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.

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Benchtop Lathe Gets An Electronic Leadscrew Makeover

April 17, 2019 by 51 Comments

The king of machine tools is the lathe, and if the king has a heart, it’s probably the leadscrew. That’s the bit that allows threading operations, arguably the most important job a lathe can tackle. It’s a simple concept, really – the leadscrew is mechanically linked through gears to the spindle so that the cutting tool moves along the long axis of the workpiece as it rotates, allowing it to cut threads of the desired pitch.

But what’s simple in concept can be complicated in reality. As [Clough42] points out, most lathes couple the lead screw to the spindle drive through a complex series of gears that need to be swapped in and out to accommodate different thread pitches, and makes going from imperial to metric a whole ball of wax by itself. So he set about building an electronic leadscrew for his lathe. The idea is to forgo the gear train and drive the leadscrew directly with a high-quality stepper motor. That sounds easy enough, but bear in mind that the translation of the tool needs to be perfectly synchronized with the rotation of the spindle to make threading possible. That will be accomplished with an industrial-grade quadrature encoder coupled to the spindle, which will tell software running on a TI LaunchPad how fast to turn the stepper – and in which direction, to control thread handedness. The video below has some great detail on real-time operating systems on microcontrollers as well as tests on all the hardware to be used.

This is only a proof of concept at this point, but we’re looking forward to the rest of this series. In the meantime, [Quinn Dunki]’s excellent series on choosing a lathe should keep you going.

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Fake Omron Relays Are Worth What You Pay For Them

May 11, 2018 by 40 Comments

We love taking a look at fake components and [BigClive] has put together something really special in this category. When he saw he could buy suspiciously cheap Omron relays on eBay, he knew something must be fishy so he put in an order.

Some of the fakes he received are even marked Omrch instead of Omron, and your ear can detect the counterfeits by the varying sounds they make during operation. But of course [Clive’s] investigation goes much deeper than that. He started driving the relays to their rated voltages and taking temperatures with a FLIR camera.

The results were not surprising. At lower voltages the relays seemed to do okay, but closer to the maximums it’s obvious the components in the fakes are not rated for enough power to work. You can even see some charring of a resistor and its plastic holder from having too much power for the component’s rating. [Clive] actually replaced the errant resistor with a higher value resistor that reduces the current consumption and power dissipated.

He was also suspicious of the metal content of the contacts. You may think that doesn’t matter, but actually, the composition of relay contacts is critical to making reliable relay circuits. Depending on how much current flows and if the switching is dry (that is, made without current flowing) or not dictates use of different material.

The conclusion was that these relays might work for light duty projects, but for commercial projects or operating near the edge of the ratings, you want to give these a pass. If you do need a lot of low-power relays on the cheap — to compute a square root, or to build the whole computer — [Clive’s] process of testing and characterizing these fakes may come in handy for you.

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