pturmel

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About pturmel

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  1. help with first time program

    If you are comfortable with logic with real relays, then you should adapt to PLC ladder logic easily.  The digital I/O part of a PLC platform can be considered a black box with a nearly unlimited supply of tiny interposing relays, each with a nearly unlimited supply of tiny contacts of many kinds.  PLC input cards feed dedicated virtual interposing relays with contact that you use anywhere in your logic.  You create and use other virtual relays in your code, including options for latch/unlatch coil pairs.  PLC output cards are similar to these virtual relays, but include a physical electronic or mechanical contact to drive real-world loads. PLC's also provide virtual relays that mimic real-world timing relays, mechanical counter mechanisms, et cetera. The techniques common for real relay logic, like seal-in branches, are commonly used in PLCs, too.  Just with virtual contacts instead of real ones. One application note:  stop buttons and similar devices that need to fail in the "off" position are usually wired to a real-world normally closed contact, and then used with opposite virtual contacts in the PLC. On the analog side, PLC platforms emulate many different kinds of analog switches, with nearly any kind of math functions you like. So, the relay part of your real boiler control should look very similar when translated into PLC ladder logic.
  2. That's nice, but it seems to be opposite direction of the OP's question.
  3. CC-Link IE Protocols

    Interesting link.  As a collection of best practices and techniques for determinism, TSN is great.  As an implied sole solution for determinism, the way it is marketed and twisted into some commercial products, not so great.  Especially as a newcomer whose core is technology has been standard in Rockwell products for many years.  Like, more than a decade.
  4. You can't edit them online, but you can create new ones online, and online delete unused UDTs.  You can create new tags with new types online, and online delete unused tags.  So if you absolutely must, you can online edit your way into new UDTs.  (For part of that time, with two complete sets of tags of those types.  Dragging and dropping from a temporary offline copy of the program, open in another instance of Studio 5000, is a big help.)
  5. This. Logix UDTs are Rockwell's implementation of structs.  There are some quirks, like its odd  and non-optional 32-bit alignment (64-bit in some case with v27+ firmware) rules.  (In summary:  single 8-bit types are byte-aligned, single 16-bit types are 16-bit aligned, all else is 32-bit aligned, including all all arrays and nested structures.)
  6. CC-Link IE Protocols

    PTP packets can be priority-marked, too.  And PTP-compliant switches measure and report latency across the switch itself to maintain accuracy.  TSN incompatibilities are simply attempts repurpose existing technologies with vendor lock-in.  I'm less than impressed.  (Not that it doesn't work, but that there's a bunch of hype.) Logix processors provide detailed information about their active grandmaster clock (via GSV), so the alarming is possible and configurable.
  7. Yes, you must tie the commons together when using that card.  It is not isolated.  If you need isolation, you must use the 1756-IF8I.
  8. CC-Link IE Protocols

    Rockwell has been using the same time synchronization technology as TSN for many years--IEEE 1588, also known as Precision Time Protocol.  It is a fundamental part of CIP Sync, the TSN-ish extension to EtherNet/IP and related technologies.  So, no, CC-Link is not first in this space.  They are just using the fancier new buzzword.
  9. Yeah, that calls for a SCADA system and database to feed the PLC.  The SCADA would load several centimeters of data into a ring buffer in the PLC, then dynamically load more from the database as the servo advances. This is exceedingly non-trivial.
  10. Siemens

    Mwah, ha, ha, ha! Compare the native languages of the people who designed them.
  11. Measure carefully.  The bulk of the time caused by the diode will be between output turn-off and the valve beginning to close.
  12. Well, the coil is the item storing energy, and producing the reverse voltage when the driving voltage quits.  With a diode, the reverse voltage peaks at ~0.7V.  With an MOV, that reverse voltage peaks at the MOV's breakdown rating. With neither diode nor MOV, that reverse voltage peaks at spark initiation in the wiring, or at the failure reverse voltage of the driving circuit. For the pedants among us engineers. (:
  13. One more note:  when switching solenoid coils that fast, use heavy-duty Metal-Oxide-Varister suppressors on the coils instead of flyback diodes.  Flyback diodes greatly lengthen the time it takes for solenoids to turn OFF.  Probably too much for 10ms cycles.  MOVs apply reverse voltage to the coil such that they turn off about as quickly as they turn on. Some digital output modules from various brands include flyback diodes right in the digital output.  You must not use that kind of output module, for this same reason.
  14. This sounds like a typical PLC application.  You will almost certainly be disappointed trying to switch valves that fast with Modbus RTU.  You will want those coils wired individually to output modules mounted directly to the PLC's CPU. I'm not familiar enough with the Modicon family's motion control capabilities to know if it will be responsive enough.
  15. SAIA PLC - Modbus TCP truncates 32 bit value

    Keep in mind that the floating point format issue is independent of the Modbus protocol issue.