why do plc's have so little memory still?

I agree. Total BS- PLC manufacturers are colluding against the market.

Same mindset with anti-features. They design one PLC that can do everything (motion, 256 ENet connections, etc) then disable those features incrementally throughout the line to make you pay more for what you need.

Yes!!!!! I was just thinking about this the other day because IDEC's new FC6A PLC has a very arbitrary data log file size of 5 MB.
 
i'm not going to argue. just going to say, follow the money. and yes, it probably totally the supply and demand. there were some points that actually i could tear to shreds. not going to do it.
 
Staring into my crystal ball and peering a few years into the future when it is typical for a PLC to have all the memory some of the posters in this thread seem to desire, I foresee a thread complaining about the bloatware embedded in those same PLCs.
 
@ganut: Yup. Look at what you can get in a $30 hobby board and tell me we're not getting screwed. Look at all this goodness: http://linuxgizmos.com/catalog-of-98-open-spec-hacker-friendly-sbcs/

Related, after contacting IDEC support about that very arbitrary 5 MB limit, I decided that my company's products will no longer use PLCs except as I/O gateways. DIN rail mount PC will run Linux and do everything important faster and better.
 
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Staring into my crystal ball and peering a few years into the future when it is typical for a PLC to have all the memory some of the posters in this thread seem to desire, I foresee a thread complaining about the bloatware embedded in those same PLCs.

Not going to disagree, because it will probably run Windoze embedded in some shape or form. Software cancer.
 
I'm not going to defend the practice too hard, but I have been on the flip side a bit, and one MAJOR issue is longevity of not only the device itself, but the support for it too. So are industrial PLCs lagging behind desktop and cell phone technology? Sure. But they have to make them to LAST.

Now... how old is YOUR cell phone? 1 year? 2 years? Maybe 3? In my experience after 3 years, they no longer function. My PCs? Same thing. If I don't keep upgrading, I can't use them after a few years and then after 5, I can't even upgrade them any more, nothing works with the old OS after a while and the new OS won't load into the old HW.

PLCs used in machinery that is generating revenue for a manufacturing company cannot afford the luxury of only lasting a year, or 3, or 5... There are PLCs out there running machines for longer than many of you have been alive.

I just last month was asked if I had a way to modify a program on a PLC-3 that I installed in 1979! It is STILL running! I have a PC in my shop that I abandoned in 2012, but I realized my DOS based software to program that thing was on that hard drive and tried to fire it up. No joy, I had to remove the HDD and slave it to my laptop. Then I had to create a VM that would run DOS, then find a way to spit out RS-232...

But again, that was to CHANGE the programming. That PLC is still running, pushing on 40 years now.
 
As with any product, the quality depends on the quality of the components, which is not necessarily always tied to price -- there are not so cheapo PLCs and HMIs that fail when you breathe wrong at them, and there are expensive PCs/PC components that don't even work on out of the box quite frequently.

But, thanks to Linux, I used an ASUS netbook from 2008 until a few months ago, and I only threw it out because it was slow, it still worked just fine. We have other PCs at my work that have been in use since the early 2000s. PCs weren't reliable enough 20 years ago, but they can be now with proper component manufacturer selection. They will last for decades too, given the chance.

But yeah, I'll give props to a PLC still running from 1979. That's got to feel great for you as the installer, and that's pretty impressive for the product as well.
 
I think safety and product testing all so play a big part here.

If an Arduino looses an input okay, cool your flowers didn't get watered

A PLC has a failure and it can get expensive in a hurry, if no one is hurt. Not that these things don't break, they do all the time just a little less often.

There is a lot of money wrapped up in making sure it works for years to come so you gotta pay to make up for that.
 
@ganut: Yup. Look at what you can get in a $30 hobby board and tell me we're not getting screwed. Look at all this goodness: http://linuxgizmos.com/catalog-of-98-open-spec-hacker-friendly-sbcs/

Related, after contacting IDEC support about that very arbitrary 5 MB limit, I decided that my company's products will no longer use PLCs except as I/O gateways. DIN rail mount PC will run Linux and do everything important faster and better.

In my experience, for you to get away with installing a system based on a Linux SBC you'd have to be selling something that no one else had... and that would be hard as well if you weren't in charge of the manufacturing of said boards. No one would be willing to pay reengineering time when a controller went down because you couldn't source parts.

I've seen stuff like that in the field... but the manufacturer makes their own controllers and IO's and there is perhaps one manufacturer that offers something remotely similar to their product so there's no real choice there. One thing that they also have is a fairly open system where you see exactly what the program is doing, despite not being able to modify it... I can only imagine the amount of hours taken to develop something like that.
 
Why do you seem to have such a hatred toward AD? Have you personally had issues with there stuff before?

not my hate. just the feeling in the industry of others. If I put a harbor freight product in a 250k piece of equipment, the customer is going to feel jipped.

only experience w/ harbor freight has been the direct logic plc's. the power supply goes out and it a paper weight.

disconnects: look cheap, are cheap, and act cheap.
 
I think safety and product testing all so play a big part here.

If an Arduino looses an input okay, cool your flowers didn't get watered

A PLC has a failure and it can get expensive in a hurry, if no one is hurt. Not that these things don't break, they do all the time just a little less often.

There is a lot of money wrapped up in making sure it works for years to come so you gotta pay to make up for that.

i knew people would latch on to the arduino comment.
I am pro plc. The robustness, the runs for decades, the fact that you can just kill power (no safe shut down), et al.

but, doesn't have ANYTHING to do w/ memory. more memory! give me a micro sd slot. anything.
 
I realize that i am whining. the pros of plc's far out weigh the cons. i'm pro plc. in fact, the fact that plc's follow advances in technology at a reduced pace is for the most part a blessing in disguise.

gives us old farts time to catch up.

but, it time for cheap memory already, just saying.
 
not my hate. just the feeling in the industry of others. If I put a harbor freight product in a 250k piece of equipment, the customer is going to feel jipped.

only experience w/ harbor freight has been the direct logic plc's. the power supply goes out and it a paper weight.

disconnects: look cheap, are cheap, and act cheap.


Do you realize that the DirectLogic PLC line is over 20 years old? It's like comparing a ControlLogix to a PLC 5.

ADC has several newer PLC lines that are absolutely nothing like DirectLogic. New instruction sets, new hardware and new software. ADC has grown up quite a bit in the market. If you haven't looked at the new PLC lines, I would urge you to do so. You might just find what you are looking for.
 
I'm seeing a lot of people in general referencing Arduinos in these types of conversations, but it's kind of an unintentional strawman. To me, it's like saying "this ControlLogix is way better than your DOS machine from 1988".

Arduino makes many different models, but colloquially this refers to their Uno model, which is a lame 16 MHz 8-bit CPU with no FPU, basically representing the early days / dark ages of hobby boards. They did this on purpose so they could get something cheap, available, and simple out for students and hobbyists to play with. Those CPUs cost cents.

Same thing with Raspberry Pi, the first one really sucks, it's an outdated ARM chip that doesn't even have out of the box support for most Linux distros (at least it didn't until people went nuts about them).

Getting to the point, the hobby/maker market is now FLOODED with new and better stuff. Most Linux boards have multi-core modern ARM chips that you would find in your phone, with specs to match. The non-Linux ones are also using modern ARM chips, but of the microcontroller flavor (Cortex-M, not Cortex-A).

Relevant question, has anyone else seen OPTO 22's digital I/O system for the Raspberry Pi?
 

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