A 1960s PLC Gives Up Its Secrets

When it comes to process automation, the go-to part in most industrial settings is a Programmable Logic Controller, or PLC. These specialized computers will have a modern microcontroller running the show, but surprisingly the way they are programmed still has echoes of a time before electronic PLCs when such control would have been electromechanical.

[Thomas Scherrer] has an interesting design to tear down, it’s a Siemens electromechanical motor controller from the early 1960s. It’s not quite the huge banks of relays which would have made a fully-blown PLC back in those times, but it’s a half-way house with some simple programming capability in the form of several channels of adjustable time delay.

We’re partly sad to see this unit being subjected to a destructive teardown, but nevertheless it’s interesting to see all those very period components. The current sensor has a mechanism similar to a moving coil meter, and the four-channel timer is a mechanical sequencer with four adjustable cam-driven switches. We’re not sure we would be cracking open selenium rectifiers with such nonchalance though.

These units were built to a very high quality indeed, and though it’s obvious this one comes from a decommissioned installation it’s not beyond possibility to think there might be some of them still doing their job over six decades after manufacture. Have any of you seen one of these or something like it in operation recently? Let us know in the comments. Meanwhile the video is below the break.

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Humble Arduino As PLC

On the surface, a programmable logic controller (PLC) might seem like nothing more than a generic microcontroller, perhaps outfitted to operate in industrial settings with things like high temperatures or harsh vibrations. While this is true to some extent, PLCs also have an international standard for their architecture and programming languages. This standard is maintained by the International Electrotechnical Commission, making it so that any device built under these specifications will be recognizable to control engineers and maintenance personnel worldwide. And, if you use this standard when working with certain Arduinos, this common platform can become a standard-compliant PLC as well.

The IDE itself supports programming ladder diagrams, functional block diagrams, and other programming systems covered under the IEC 61131-3 standard. Not only that, it allows the combination of these types of PLC programming with Arduino sketches. The system offers many of the perks of PLC programming alongside the familiar Arduino platform, and supports a number of protocols as well including CANOpen, Modbus RTU, and Modbus TCP. It can also be used for monitoring a PLC system, essentially adding IoT capabilities to existing systems, enabling continuous monitoring, debugging, and program updates.

While not every Arduino is a great platform to build a PLC around, there are a few available for those looking for a system a little less proprietary and a little more user-friendly than typical PLC systems tend to be. There’s a reason that PLCs are built around an international standard and generally have certain hardware in mind to run it, though, and this comparison of a Raspberry Pi with an off-the-shelf PLC goes into detail about why certain components aren’t good choices for PLCs.

Automate Away The Drudgery Of CNC Manufacturing

One of the keys to making money with manufacturing is to find something that you can make a lot of. Most small manufacturers have one or two “bread and butter” items that can be cranked out in quantity, which of course has a quality all its own. The problem with that approach, though, is that it runs the risk of being boring. And what better way to avoid that than by automating your high-volume job, with something like this automated  CNC work cell?

Looks like money.

[Maher Lagha] doesn’t offer too much in the way of build details, but the video below pretty much tells the tale. The high-volume items in this case are customized wooden coasters, the kind a restaurant would buy for their bar or a business would give away as swag. The small 3-axis CNC router at the center of the work cell is the perfect choice for making these — one at a time. With no desire to be tied to the machine all day to load raw stock and unload completed coasters, [Maher] came up with automated towers that hold stacks of pallets. Each pallet, which acts as a fixture for the workpiece through multiple operations, moves from the input stack into the router’s work envelope and to the output stack using a combination of servos and pneumatics. The entire work cell is about a meter on a side and contains everything needed for all the operations, including air for the pneumatics and dust extraction.

Each coaster requires two tools to complete — one for surfacing and one for lettering — and [Maher] has two ways to tackle that. The first is to allow a stack of coasters to go through the first operation, change tools, and switch the roughed-in stock back to the input stack for the second round of machining. The other is just to build another work cell dedicated to lettering, which seems to be in progress. In fact, it looks as if there’s a third work cell in the works in [Maher]’s shop. The coaster business must be pretty good.

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An Affordable And Programmable PLC

We’re all used to general purpose microcontroller boards such as the Arduino or its many imitators, but perhaps we don’t see as much of their industrial cousins. A programmable logic controller (PLC) is a computer designed to automate industrial machinery, and comes with protected interfaces and usually a specific PLC programming environment. Thus [Galopago]’s work with an inexpensive Chinese PLC clone is especially interesting, providing a route forward to using it within the Arduino IDE ecosystem.

Opening it up, the processor is identified as an STM32F103, and the connection needed to place it in bootloader mode is identified. Then it can be programmed from the Arduino IDE, even though its bootloader can’t be changed. Then to complete the process it’s necessary to identify the various different inputs and outputs by old-fashioned hardware reverse engineering.

This PLC may not be quite as robust as some products costing much more money, but it still represents a cost-effective way to access a microcontroller board with much of the interface circuitry already installed that would normally be required for controlling machinery. We expect that we’ll be seeing it appear on these pages over the coming months, and perhaps there might even be another comparison in the air.

Jared Holladay

The Safest Model Roller Coaster

[Jared Holladay] is a computer engineering student at the University of Cincinnati and a life-long roller coaster fanatic. A lot of people look at roller coasters as an exciting example of physics, like potential energy versus kinetic energy or inertia, and rightly so. [Jared] looks at them and wonders about the controls. Video also below and there is a feature-length explanation with more details. Some Hackaday readers and writers can identify the components, so we think his coaster model belongs here.

Like many folks in this field, he’s built K’nex models to get a handle on construction. He’s toured STEM shows with the tracks and undoubtedly wowed kids, adults, and physics teachers, but since he can speak to the programming, he is a triple threat. Now, he’s growing out of the toy construction plastic and moving into 3D printed parts with needle-fine tolerances.

His latest base is extruded aluminum, like what you’d want in a rigid CNC or printer. In addition to the industrial-grade surface, Rockwell Automation sent him a safety programmable logic controller, PLC, and a touchscreen HMI. Our fellows in the industry tell us those are far beyond the price scope of regular hobbyists. But fear not; your Arduino clones will suffice until you get your first grant.

The point of all the ruggedized hardware, aside from authenticity, is to implement safety features the same way you would in the industry. The redundant PLC connects to inductive prox sensors to check train speed and location. Other moving parts, like friction brakes, have sensors to report if there is a jam. After all, it’s no good if you can’t stop a train full of people. There are hundreds of things that can go wrong. Just ask [Jared] because he programmed on-screen indicators for all of them and classified them to let an operator know if they can keep the ride moving or if they need to call maintenance.

Not all homemade coasters are scale models, and some of the traditional ones have more than meets the eye.

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Samsung tablet with custom side loaded hack software

Smart Home Hack Breaks Down Walls Figuratively And Literally

Are you ready for a tale of poorly supported hardware, clueless contractors, and bad coding? Look no further than [Neighborino]’s excellent write-up where he details his pursuit of smart home pwnership.

[Neighborino]’s smart home system controls the windows, blinds, outlets, and HVAC. But by the time the high-rise apartment was ready for occupancy in 2015, the smart home controllers were already showing their age. You see, the contractor had installed an app to run the home’s programmable logic controllers (PLCs) on stock Galaxy Tab 3 hardware. Yes, that’s a tablet originally released in 2013. They then built the tablets into the wall of each apartment, dooming the homeowner to rely on the vendor forevermore.

It was not long before [Neighborino] and their fellow residents were dealing with stability problems. Bloatware from both Samsung and Google was causing major slowdowns, and the PLC system’s unpublished WiFi password prevented replacement of the controllers.

Being an Android developer by trade, [Neighborino] set siege to the walled garden before him. The writeup details the quest to execute what would be a straightforward hack on anything but the x86 hardware that was being targeted.

de-bloating app strips all non-essential software.
A debloating app strips all non-essential software.

The first fruit of [Neighborino]’s efforts was a hack for the aged tablets that would display the WiFi password, allowing owners to connect their own controllers to their smart homes. Of course, this is Hackaday, so you know that [Neighborino] didn’t stop there.

Despite having to deal with two different versions of Android and tablets that were built into the wall of the apartments of non-hacker neighbors, [Neighborino] succeeded in sideloading an APK. This freed them from the shackles of the company that installed the original system and gets longer life out of their Snowden-era Samsungs. A de-bloating tool frees up memory and restores the systems to a nearly performant status. A reboot scheduler keeps the x86 tablets running without user intervention, and of course the WiFi password revealer makes yard waste out of the previously walled garden.

If Smart Home hacks are your thing, we recently covered a Voice Controlled Smart Home setup, and less recently another that combined a Smart Home with a Dumb Terminal. Be sure to share your own smart home hacks with us via the Tip Line!

SCADA Security Hack Chat

Join us on Wednesday, July 14 at noon Pacific for the SCADA Security Hack Chat with Éireann Leverett!

As a society, we’ve learned a lot of hard lessons over the last year and a half or so. But one of the strongest lessons we’ve faced is the true fragility of our infrastructure. The crumbling buildings and bridges and their tragic consequences are one thing, but along with attacks on the food and energy supply chains, it’s clear that our systems are at the most vulnerable as their complexity increases.

And boy are we good at making complex systems. In the United States alone, millions of miles of cables and pipelines stitch the country together from one coast to the other, much of it installed in remote and rugged places. Such far-flung systems require monitoring and control, which is the job of supervisory control and data acquisition, or SCADA, systems. These networks have grown along with the infrastructure, often in a somewhat ad hoc manner, and given their nature they can be tempting targets for threat actors.

Finding ways to secure such systems is very much on Éireann Leverett’s mind. As a Senior Risk Researcher at the University of Cambridge, he knows about the threats to our infrastructure and works to find ways to mitigate them. His book Solving Cyber Risk lays out a framework for protecting IT infrastructure in general. For this Hack Chat, Éireann will be addressing the special needs of SCADA systems, and how best to protect these networks. Drop by with your questions about infrastructure automation, mitigating cyber risks, and what it takes to protect the endless web of pipes and wires we all need to survive.

join-hack-chatOur Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, July 14 at 12:00 PM Pacific time. If time zones have you tied up, we have a handy time zone converter.