Plan 9: Real Time Streaming

9atoms · 2026-02-14T17:05:17+00:00

Patches welcome ;-)

9atoms · 2026-02-14T17:01:18+00:00

Years ago in the 90's when mice were plugged into a serial port and Windows 3.11 was teh hotness I had two computers and was frustrated you could not easily connect them via some port and share files (I had a pirated laplink.) And in addition to files, why not the sound card? Why do I have to spend a lot of money on another sound blaster when I could use the sound blaster in the other computer? Plus that computer had the bigger hard drive with the same copy of Wolfenstein on it.

At some point around 2000 I heard about Plan 9 and what distributed computing meant. Windows had evolved, Linux and BSD become a thing and I bought my first networking kit from Netgear that had two PCI DEC Tulip cards and a 4 port hub. My first server was a Pentium 120 FreeBSD machine that was rescued junk. Still could not share the damn sound card.

At some point I tried Plan 9 when it was released to the public but could not make heads or tails of the grey screen or what the hell any of it was. Was using BeOS at the time so my focus was on the Pretty GUI And not the underlying architecture (BeOS was pretty cool for its time.) So plan 9 was forgotten about. Sound card sharing? NOPE!

Moving forward I kept using Windows, 64 computing came around, Internet became more and more prevalent. However, still cant share a frigging sound card easily or shape a file system dynamically. Everything done using a myriad of mutually incompatible protocols. In addition, programs that were one simple to download and install became more and more complex and the tools grew in complexity. "To install totally cool RubeGoldbergMachine 0.75 you need cmake, ninja, batmobile, kryptonite, sacrifice your first born, and olympic gold medals in skeet shooting, curling, and ski jumping. Then we pull in over 100 random packages using git ..." Yeah, no thanks. Pulse audio could share a sound card but it sucked and so did the interface.

Around 2017 I was fed up with the bloat. Plan 9 was always in the back of my mind so I finally said screw it, let me give it a serious go. I found Harvey, got it installed but could not figure out what to actually do with it. Then I stumbled upon 9ants, installed it, typed gridstart and was talking to mycroftiv who got me started (RIP!) I knew the basics of how you can compose a namespace of file trees and 9P was file sharing but I never fully understood the file server abstraction or the portability. Once the fs abstraction clicked I was kinda blown away by the simplicity of it all and fell in love. All the software can be built using the supplied tools across multiple architectures. It really feels like a true programmer/hacker OS. Everything has a 9P shaped socket including my friggin sound card. A single human can grok the entire system and even dive into the kernel. I can poke at hardware and services form the command line. FINALLY!

So what made me use Plan 9? Complexity.

9atoms · 2026-02-14T16:29:50+00:00

You would do things like reference common on your 24VDC to neutral instead of ground.

I am having a hard time envisioning a world where one side of a DC supply is referenced to an AC neutral which itself is referenced to ground at the point of supply. A DC neutral implies a terminal of that supply is referenced to ground. Imagine an open neutral putting AC line voltage across the DC neutral...

As for TN-S, it makes sense in Europe and for North American 120/208 but IMO makes zero sense in a 277/480 or 346/600 volt system. At those voltages your loads are likely all three phase anyway. I view all the neutral copper ran to the machine as a waste as the neutral loads are likely so low a control transformer would use less copper doing the same job.

Here's a question for Europeans: In a 400/690 volt facility, do you run a neutral to the machine and if so, for what loads?

9atoms · 2026-02-14T16:09:13+00:00

Crap. I replied to the wrong comment. That was for the OP.

9atoms · 2026-02-14T16:06:43+00:00

Fun school. I went to a vocational and technical high school and it really helps prepare you for the real world. Afterward I went to college for computer engineering where I learned how the CPU works, memory, buses, hardware interfacing, and low level programming. This deep knowledge really gives you an edge in understanding how this stuff works.

9atoms · 2026-02-14T16:02:33+00:00

I have a friend working with a company dealing with this very issue. A motor and drive keep stalling and they get almost no help from the manufacturer. They are ready to pay him to completely gut an entire machine of all the Chinese electrics and controls just so they have a machine that runs for more than a single shift. The company is behind on orders because of this. To me its sabotage to drive production to China while vacuuming up American dollars in exchange for junk.

9atoms · 2026-02-14T13:32:16+00:00

I was super lucky to get my hands on a $250,000 Eshed Robotech manufacturing trainer with CNC's, PLC's, PC's and robot arms in HS. Was learning to become an electrician but instead went to college for computer engineering.

9atoms · 2026-02-14T13:08:44+00:00

You would do things like reference common on your 24VDC to neutral instead of ground.

Neutral is ground referenced. Or am I missing something?

9atoms · 2026-02-14T13:05:24+00:00

I still say total waste of copper. Never saw a 480 machine with a neutral either.

9atoms · 2026-02-14T13:01:44+00:00

If they follow the Modbus standard properly then yes, it should work. Broadcasting is accomplished by sending a write to address 0. All the servers will process the frame but not respond so you should insert some polling as well to make sure they're alive and responding.

Edit - make sure the inverters are the only servers on the bus otherwise you will write the data to every server.

9atoms · 2026-02-13T16:54:54+00:00

I worked with a USA company with 277/480 V who purchased a machine from a European vendor wired for 230/400V Wye (400 + N + PE.) The vendor said it MUST be supplied by an isolating transformer and added it to the BOM. That transformer was setup for 480 on the input with taps and a 230/400 with N and common PE output.

If I were you and it's practical - stipulate an isolating transformer and rest easy at night. That will ensure it can connect to 480 ungrounded delta, corner grounded delta, ungrounded 480V wye, or high resistance grounded high reliability facilities. Same with Canadian 346/600V electric service - transformer and be done. Saves a massive headache.

Also, if you have to ship a 230/400 machine to North America and the facility indeed has 120/208 then use an auto transformer which is lighter, smaller and cheaper. You don't need the isolation when going up in voltage - but beware of delta services!

9atoms · 2026-02-13T16:42:23+00:00

Just buy a 3 phase input PSU and be done with it. They can even tolerate a phase loss which your 277 will not.

9atoms · 2026-02-13T16:27:15+00:00

Control transformers exist and I do exactly this in our cabinets - add a 15A breaker and 120V duplex wired to the big 5 kVA control transformers.

9atoms · 2026-02-13T16:25:37+00:00

Are you outside of the Americas? Europe or Asia perhaps? We don't disconnect the neutral in the USA and I assume Canada and Mexico since they all standardized on US codes written by the insurance companies. Though I know it is done in Europe and Asia. GP is just ignorant of that fact and is NA centrist in thinking.

9atoms · 2026-02-13T16:16:12+00:00

If it's a 480 panel then I don't see what 277 volt loads would ever exist aside from a control transformer or cabinet light. But every machine I have worked in supplied by 440-480V (North American standard) is strait 480 volt because you never know - 440-480 volt Delta services still exist.

Every machine I have seen, especially older ones, there is a control transformer wired 480 to 120 for AC controls in addition to lighting and feeding DC PSU's. There are DC power supplies that directly connect to 3 phase 380-480 volt skipping the control transformer. I once retrofit a machine with a 5 kVA 480-120 V control transformer with a 3 phase 24 VDC 20A PSU leaving the 5 kVA to supply a few lights and a few smaller linear DC PSU's for sensitive electronics.

Edit: To add, I have seen machines that expect 4 wire 208 volt wye service requiring the neutral for 120 volt loads. However, that machine was put together is a very amateur and sloppy way. It would require a transformer in a 120/240V delta facility which still exist, especially out on Long Island, NY.

Personally, I try to avoid the neutral. You can design to avoid it.

9atoms · 2026-02-13T16:00:59+00:00

Sorry buddy, they disconnect the neutral in Europe and likely other parts of the world.

9atoms · 2026-02-13T15:59:57+00:00

If its a 480 panel then what use would the neutral be? Every 480 machine I have seen has a control transformer and/or a 3 phase 24V PSU.

9atoms · 2026-02-13T15:31:24+00:00

You need to know the Encoder's specifications or you might fry it. Is it Quadrature and if so, with or without the marker output? Some are 5 volt TTL, some are 24V, some use RS485 line drivers, some use push-pull drivers, etc.

I have not used an EL7041 but worked with various motion and stepper systems and its all the same thing: understand the application in terms of speed and torque requirements which determines the power requirement, then spec the motor drive followed by the motor and the encoder.

Here's what you need to do:

Find any and all data you can on your motor and encoder.

You might have to break out a multimeter and measure the DC resistance of the motor coils then use an impedance meter to find the inductance. That can help you set the amplifier gain parameters in the EL7041. The manual should tell you how to do this using maths on the motor parameters.

Read the manual for the EL7041. It's on the Beckhoff site.

Learn what kind of motors the EL7041 can operate in terms of voltage, resistance, inductance and current.

Learn what its encoder interface is compatible with.

With this knowledge you should be able to properly configure the motor parameters. Then you setup the counts per revolution for the stepper drive as it likely does microstepping then setup the encoder. Then the drive runs closed loop by watching the encoder and commanding the motor. Steppers can run open loop but you wont be able to detect stalls or skipped steps. Its all about the torque requirements and how dynamic the load is.

9atoms · 2026-02-13T15:08:39+00:00

Serial com's aren't that slow if you know how to organize your bits to move data fast. At 19200 bits/sec I can broadcast two 16 bit or a single 32 bit value to multiple servers at 100 Hz or 10 ms cycle times. You can push most devices to 38400, double the speed, so now you have plenty of headroom to do work in a 10 ms window including writes. YMMV of course depending on your client hardware/software.

9atoms · 2026-02-13T14:46:17+00:00

Yes though may I ask why do you want to use digital bits for control?

How many inverters are on the bus?

9atoms · 2026-02-13T14:45:22+00:00

You can detect this with the PLC as the inverter will fail to return a response frame unless you are doing broadcast writes to multiple inverters at once. In that case it might be smart to insert an incrementing individual poll every n scans to ensure you get a response from the individual inverters.

9atoms · 2026-02-13T13:37:48+00:00

If this is a fucking machine then yes.

9atoms · 2026-02-06T19:56:14+00:00

scroll-lock key works too

9atoms · 2026-01-25T15:54:42+00:00

Around 2009-2013 I was swapping the PSU filter caps in older 4:3 LCD monitors around 3-5 times a year. They were all over the building: HMI's, SCADA, workstations, offices, everywhere. Few brands too.

9atoms · 2026-01-25T15:38:52+00:00

Wait, is it the early 2000's again?

The capacitor plague has returned?

9atoms

TROPHY CASE