ganutenator
Lifetime Supporting Member
OP
you used to blow my mind by rolling your own pid's back in 2002.
why do plc's have so little memory still?
- Thread starter ganutenator
- Start date
you used to blow my mind by rolling your own pid's back in 2002.
If you don't like it, don't buy it
V0N_hydro
Member
It is pretty amazing being able to modify the PLC program running the process without stopping the process. On-line changes to the program seems to be a real line in the sand for PLCs.
Are there other platforms that allow it?
Are there other platforms that allow it?
Fantastic question, I have been looking into this for quite sometime and apparently this can (cross-platform): https://www.eclipse.org/4diac/
For those of you unfamiliar with Eclipse, they are the makers of the Eclipse IDE, which is the de facto standard IDE for Java, the world's most popular programming language.
I stumbled across that software a few months ago, don't remember how, but I had never heard of IEC 61499 before that.
Peter Nachtwey
Member
That is nothing.
Our old RMC100 permitted over writing the old program on-the-fly.Von Hydro said:
Ravioli
Member
I'm amazed at the price difference between a ControlLogix 2MB 1756-L71, and a 32MB 1756-L75. I doubt the incremental cost of 30MB memory is close to the 4x price tag.
He said PLC, but I guess I had interpreted it a little broader, as including most of the traditional industrial control options. PLCs typically can have program changes in runtime, and I've seen the same for SCADA systems. I don't have enough experience with motion controllers to know, but at the very least I assumed that they often could do that as well.
The 4diac link mentioned there looks interesting. It LOOKS like it is supposed to be, essentially, a cross platform PLC firmware. But NEXT GEN because it supports some new standard instead of the old one. Could be cool?
I don't know much, haven't used it, but my understanding is that IEC 61499 is a function-block based upgrade to IEC 61131, and includes the option to do code in 61131-3 languages. The aim is for distributed control vs. local.
4diac comes with an IDE (like RSLogix etc.), and runtime environments that you can put on computer-based devices. Notably, it has built-in support for MQTT, Modbus RTU/TCP, and OPC UA. The limitation right now is that I don't think any PLC supports 61499, so you are left to using computer-based devices, such as a Wago PFC, or anything that runs Windows or Linux.
4diac comes with an IDE (like RSLogix etc.), and runtime environments that you can put on computer-based devices. Notably, it has built-in support for MQTT, Modbus RTU/TCP, and OPC UA. The limitation right now is that I don't think any PLC supports 61499, so you are left to using computer-based devices, such as a Wago PFC, or anything that runs Windows or Linux.
I think you're right about the two standards, I was just being vaugue. It contains some interesting steps forward, but I'm curious to see how beneficial it actually is. The original IEC 61131 has been just "good enough" for decades, because most manufacturer takes whatever ideas that it likes, and then adds proprietary extensions on to fill in the gaps.
However, I think you're missing the point when you say that no PLC supports 61499. Think of 4DIAC like Codesys, where it is an open platform that pairs an engineering package with a runtime (PLC firmware), and then companies can build products based on that platform. The web site says they're working on support for B&R specifically, as well as VxWorks, which is what a number of embedded devices are based on. This includes PLCs like the ControlLogix Family. This doesn't mean you could download to a Logix processor from 4DIAC, but it does mean that companies may start basing products on this in the future. In the meantime, they list a number of PC based systems (that include controllers. It is possible that those systems are already utilizing 4DIAC in the background.
As you say, this could be great for distributed applications. They list some hobby boards you can use it with, but i'd be really curious to try this on the Siemens IoT2040 or a ruggedized RPI. At a minimum, it could be interesting for RTU type systems.
Maybe. But a lot of how well a board performs/survives depends on all of those little chips that surround said Atmel chip. But your point is well taken, there's not a bit of difference in the actual component.
And I wouldn't be surprised to hear that the "lowly" 8051 market still out sold the desktop market. By an order of magnitude...
FWIW, if I recall correctly, the first 5/15 (5/10? 5/12?, I forget...) that I programmed had an 80186 in it. And it was slower than a fat boy on a bicycle. And prone to crashing.
crawler009
Member
you can get a plc with several gigs of memory, the ab CompactLogix 5480 Controller. Enough space to store lots of data.
But most of the space is for Windows and data, not for your Logix (because that would be unnecessary)
But most of the space is for Windows and data, not for your Logix (because that would be unnecessary)
Peter Nachtwey
Member
PLC/5s used 68010s and 68020s by Motorola back then. Some had more than one. Yes, they were slow. Firmware programmers liked them because they had fancy and very flexible instructions that allowed all sort of addressing modes. SLCs used on 68030. Then came the RISC trend. The first Control Logix used an LSI Arm chip but since then I think Rockwell rolls their own cores. It is possible to many ARM cores along with all necessary I/O in a gate array. If the volumes are high enough, they are, it makes sense. It would be difficult if not impossible to copy and the design can be tweaked to get the features and performance they want. When newer and faster gate arrays become available it is easy to use the SAME programming to program the newer faster gate arrays.
I think we have a few designs where we programmed a RISC cpu into a FPGA. Since we didn't need it to do much we stripped out many of the features that weren't needed so we could use a smaller FPGA.
I strongly recommend getting a FPGA development kit and playing with it if you like programming PLCs. Imagine a FPGA based PLC that does everything in parallel and has a scan time in the micro seconds.
I think Siemens has a product that is a crude version of this.
Arduinos are OK for learning but for anything serious I would use a ARM chip because they don't cost that much more and the programming is so much easier.
The ControlLogix CPU I took apart has a Phillips (now NXP) custom ARM chip for the CPU and backplane comms. Same ARM architecture used everywhere....phones, tablets, networking devices, TVs, etc.
"Arduinos are OK for learning but for anything serious I would use a ARM chip because they don't cost that much more and the programming is so much easier."
No one should be using the original Arduino Uno for anything serious because again, it's a 16 MHz 8-bit processor with no FPU. The Arduino Due has an 84 MHz 32-bit ARM Cortex-M3 which is much more suitable for example. My favorite though is the newest Teensy (3.6), which rocks a 32-bit 180 MHz ARM Cortex-M4 with FPU for a mere $29.
"Arduinos are OK for learning but for anything serious I would use a ARM chip because they don't cost that much more and the programming is so much easier."
No one should be using the original Arduino Uno for anything serious because again, it's a 16 MHz 8-bit processor with no FPU. The Arduino Due has an 84 MHz 32-bit ARM Cortex-M3 which is much more suitable for example. My favorite though is the newest Teensy (3.6), which rocks a 32-bit 180 MHz ARM Cortex-M4 with FPU for a mere $29.
ganutenator
Lifetime Supporting Member
OP
the M340 i took apart because the 208V wire hit the back plane does too.
p.s. this thread more about memory.
about to use another bad example. the free thumb drive from the trade show had 4 gigs.
and since extremes are bad. Good Year once paid a million dollars for 1 meg of ram.
p.s. this thread more about memory.
about to use another bad example. the free thumb drive from the trade show had 4 gigs.
and since extremes are bad. Good Year once paid a million dollars for 1 meg of ram.
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