Thermo

Another factor that might be affecting the speed of response are the settings in the AC VSD.  For example it may have rate-of-change (or slew rate) settings that prevent the output frequency changing as quickly as the speed setpoint from your PLC. But as Dick has said above, the ability of your proposed system to work properly will depend ultimately on the characteristics of your process.  Centrifugal pumps have a very non-linear speed/flow/pressure relationship.  Can you post a P&I Diagram or sketch to explain what you are trying to achieve? Ian

Thanks GT.    I seem to have everything working well now and I've created a small program to add some 'smarts' to 1980s vintage sun-tracking solar hot water heater I acquired years ago. Thanks again for your help and offer of future assistance. Ian

Hi Bob & Mr Mode (or may I call you Panic?), It's horses for courses, of course.  DCS evolved for process control, PLC evolved for machine control. While I had a little to do with Honeywell TDC2000 (yes, 2000) and quite a bit with Bailey Network 90 in the late '80s.  But most of my experience had been with Yokogawa DCS since the early '90s.  A big thing about the Yoko systems is that they are absolutely deterministic.  The proprietary comms bus had a 1 sec scan time no matter how many operator stations and controller nests were installed, up to the specified maximum (and even in the 'little' uXL system that could be a massive I/O count (100,000 tags from memory?)).  The standard controller scan time was 1 sec - rock solid, no variation - which is more than enough for 99% of analog control and non-machine digital control (motor control etc.).  Fast scan for a limited amount of the program was 200ms (stop laughing, this is serious!).  But this is good enough for compressor surge control.  The newer successors (Centum CS, CS3000, VP) offer scan  times for limited  areas down to 50 ms - but again rock solid guaranteed.  I ran training on uXL for a while.  Sparkies/engineers with PLC backgrounds invariable scoff and laughed when the scan times came up but were generally impressed by the end of the training by the deterministic nature of the system and the simplicity of the total and tightl integration of the system.  Define a single DIO point or a PID control block and you automatically have a fully-featured faceplate for your HMI that is updated every second. But, as I said, 'horses for courses'.  Ian

Hi Bob, Yes, I'm a happy little Vegemite now. Gees, that would be annoying.  I know this is no place to re-start the old PLC Vs DCS discussion (for one thing, I'd be outnumbered about 1,000,000 to 1!) but clunky as it was, the old Yokogawa uXL (read: micro-XL, the little brother to Centum XL, late '80s to late '90s vintage) and it's successors, were brilliant in that regard.  Very little you couldn't do on-line/hot.   Changing analog signal conditioner cards, AIO and DIO cards and even processor cards in dual-redundant systems could all be done hot and on-line (with due regard to the effects on the process during changeover, of course).  And analog control blocks and sequence tables could be added/edited on-line.  [Sequence Table: think of a block of up to 32 rungs of ladder with up to 32 contacts and 32 coils per rung.  Packs a lot of logic into a small space.] Ah, enough reminiscing for now...

Thanks for the Zen suggestion, Mr Crossbow.  I've just read the brochure and I'm sure it would eat my simple application for breakfast.  Shame the turkey at Omron Aust didn't bother to mention it as an alternative to his $1000+ suggestion - I would have been interested.  I'm now happy I can play around with my CPM1A for the time being but I'll keep the Zen in mind should I need to do a simple 'real' project in future.  Ian

Hi pfort, It's all good now - was my misunderstanding.  I wanted to clear the memory settings and old program so I knew exactly the state of the PLC before downloading my program.  I used the function shown below. Now since I used this function, I've successfully downloaded my  program and uploaded it again to check it, and run monitoring mode etc. and all seems to be working perfectly.  However, since doing the memory clear, the comms LED and the USB adapter TX/RX  LED have been flickering constantly.  I mistook this for the 'memory clear' process taking forever, but it seems to be 'normal' for my set-up.  Does this sound right? In any case, thank you for your help. Ian

Hi GT, Bob and Jay, Many thanks for your contributions and help today and previously.  Hope you all enjoyed your stroll down memory lane.  In a parallel world I could mention the 'in-cabinet' monitoring module in the Toshiba Tosdic DCS in the early '80s and the wonderful 'fill-in-the-forms' configuration system of the Yokogawa uXL DCS.  Similarly clunky and crude by today;s standards to your old PLC programmers/software, I would think.  And showing my age too now... Jay, thanks for the old tech note.  However, even after finding an early '60s Toyota Owner's Manual to help interpret it, I still couldn't make much sense of it!

Hi Crossbow & Bob, Thank you both for your suggestions and help.  However, it seems Gtsuport's suggestion to try the Trail version of CX-One has paid off.  If only this endless Clear All Memory process will end - or have I created another monster... Ian PS: Please disregard comments about "endless Clear All Memory process".  It worked correctly and I've since downloaded and monitored my program.  It's just that the comms LED and the USB adapter LED's now flicker continuously.  But everything seems to be working, so I'm not complaining.  Ian

Hi Bob, As per my reply above to Gtsuport, it seems your idea of trying Auto Onlne worked - and after much effort to get CX-One Trail working, it did indeed reveal my PLC's comms setup. Thanks very much for your help to date and your generous offer to try to communicate with my obsolete plastic brick for me. Ian. PS: The Chinses USB cable/adapter seems to be working OK - but this Clear All Memory seems to be taking an awful long time.  Does it have to write a '0' individually to even bit in memory?

Gtsuport, You are not only incredibly handsome and charming but you are also a genius!!  What a brilliant idea (although this does not at all diminish BobB's generous offer to try my 'brick' with his Auto Online function...). It's taken all of my Saturday and half my monthly data allowance but I finally managed to download CX-One Trial and install it.  (Being is such a remote outback location (i.e. less than 2 hours from the state capital, Brisbane), we have third world or lesser internet access here...) Once I finally got it all working, Auto Online did indeed 'find' my CPM1A's comms settings - 19200 baud, 1, 7, 2, even.  The suspect Chinese USB adapter/cable preformed faultlessly.  I was able to upload the old PLC program etc. Then switched over to Win xp mode and Syswin, plugged in the appropriate comms settings, and Hey Presto! - it worked!  Many thanks to all who contributed. The current state of play is that I selected Online/Clear memory/All Areas/OK - and it's still going.  How long should this take? Thanks again all, Ian

Hi all, Some of you may have read my earlier saga of, on impulse, buying an obsolete Omron CPM1A + expansion unit and the subsequent trials and tribulations of obtaining suitable software and cable to talk to it. It's looking increasingly like my Omron-branded oversize Lego block will remain an interesting paperweight. So, given that I have a small 'home' project that I'd like to implement and have written a plausible program in Syswin for the CPM1A, what are your suggestions for a way to go if the CPM1A remains 'incommunicardo'? Automation direct have their CLICK 8/6 I/O micro PLC and cable for a low cost with, supposedly, free software.  This should have all the smarts I need for my simple program.  Any other suggestions?  Please bear in mind, this is for a home-brew project and self-training, so obvioculy I won't be spending $mega on 'all singing, all dancing' software like CX-One. Thanks all, Ian

No other takers on this topic, ladies and gentlemen?

Hi all, I'm fairly new here, as I've not had a lot to do with PLCs.  However, I have several decades experience with Yokogawa Distributed Control Systems (DCS), including uXL and Centum XL, CS, CS3000 and VP. So, should anyone be looking at replacing an aging Yokogawa DCS and need assistance decoding/reverse engineering the system configuration, please send me a PM and we can discuss. Ian

Hi Bob, I'm interested.  Have sent you a PM. Ian

Hi All, Thanks to all who helped with my first post - how to get started with a second-hand CPM1A PLC.  Thought I should now start a more specific thread. I now have Syswin 3.4 running in Windows xp mode in Windows Virtual PC, I think I have a Chinese USB-CIF02 comms cable/adapter and drivers correctly installed in Win xp mode.  The PLC powers up with the PWR and RUN LEDs lit.  The USB adapter TX LED flickers when I use the Syswin comms test function, indicating that Syswin is talking to the adapter.  But having tried 128 combinations of comms protocol and unit address at 9600 baud without success, I believe there are now two possibilities. First, while Syswin is sending something to the USB adapter, it may not be 'talking' correctly to the PLC .OR. the PLC is set for some unusual communications settings for reasons unknown, that I may never be able to stumble upon.  Both possibilities could be eliminated if I could return the PLC to the factory default state, with a known comms setup. However, it seems the comms settings in DM words are stored in Flash memory and can only be changed if I can 'talk' to the PLC - Catch 22?  I can find no sign of any DIP switches or hardware reset button etc.  Surely there must be some way to clear the flash memory to return the device to the factory default state?  All suggestions gratefully received. Ian