PLC

Browsing an OPC UA Server Against a Static Tag List: Which One, and When Each Is Wrong

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Six boxes showing what a client does during a browse: read the namespace array from node i=2255, browse the Objects folder at i=85, browse each folder in turn or in batches up to MaxNodesPerBrowse, call BrowseNext for every continuation point returned, read the attributes of each node worth keeping, and finish with a tag list, with two numbered break points naming the continuation point errors

Browsing an OPC UA Server Against a Static Tag List: Which One, and When Each Is Wrong Node i=2255 is the NamespaceArray, and one Read of it is the single most-skipped call in industrial OPC UA. Skip it and you type ns=3 into a client, which works for a year and then reads the wrong … Read more

MSO, MSF and MASD on a Logix Axis: Enabling It, Dropping It, and the One That Opens the OK Contact

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Four boxes - Stopped, Running, Shutdown, Faulted - with MSO, MSF, MASD, MASR and MAFR on the arrows between them

MSO, MSF and MASD on a Logix Axis: Enabling It, Dropping It, and the One That Opens the OK Contact An MSO against a 2198-D032-ERS4 axis sets ServoActionStatus and DriveEnableStatus, and it does not set its own .DN bit in the scan that fired it. On a 2 ms coarse update period the drive answers … Read more

The Motion Group and the Coarse Update Period: What Happens When You Ask for Too Much

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Three timelines of a 4.0 ms base update period with the motion task drawn as a coloured block at the start of each period and everything else in grey: eight axes leaving most of each period free, sixteen axes leaving little for the ladder, and twenty-four axes where the motion task fills the whole period and runs into itself, annotated with GroupFault.GroupTaskLoadingFault bit 2

The Motion Group and the Coarse Update Period: What Happens When You Ask for Too Much Bit 2 of MOTION_GROUP.GroupFault is GroupTaskLoadingFault, and the motion instruction reference describes it in plain words: the group coarse update period is too low, and user application tasks are not getting enough time to execute. That is a 1756-L84E … Read more

OPC UA Security Policies and User Authentication: What to Enable, and What It Costs

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Table of security policies against the three message security modes, showing that mode None is legal only with policy None, that Basic128Rsa15 and Basic256 are deprecated and should be left off, and that Basic256Sha256 and the two Aes policies are usable with Sign or SignAndEncrypt

OPC UA Security Policies and User Authentication: What to Enable, and What It Costs One RSA-2048 private-key operation measured 3.363 ms on the laptop this was written on, and one pass of AES-256 over a kilobyte of notification measured about 2.1 microseconds. That ratio, roughly sixteen hundred to one, is the whole of the OPC … Read more

Kinetix 5700 DC Bus Sharing: What the Bus Supply Carries and Where the Limit Is

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Two boxes joined by an orange cable: a power supply cluster holding a 2198-P208, a 2198-S086, a 2198-D020, a 2198-D006, a 2198-CAPMOD-2240 and a 2198-CAPMOD-DCBUS-IO extension module, and an extended cluster holding the same accessory pair followed by three inverters, with the customer-supplied DC-bus cable rated 104 A between them and the note that both boxes are one DC-bus group

Kinetix 5700 DC Bus Sharing: What the Bus Supply Carries and Where the Limit Is A 2198-P208 supports 13,000 µF of total system capacitance and puts out 46 kW continuously. Those are two separate ceilings, they get reached by two different kinds of machine, and on most rails the one that stops you first is … Read more

Removing an Axis From a Running Kinetix 5700 System Without Faulting the Rest

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A Kinetix 5700 rail drawn twice: as commissioned with six modules from a 2198-P208 through to a capacitor module, and again with the 55 mm 2198-D032 pulled out leaving a dashed gap, annotated with the two ways out — shift every module right of the gap 55 mm left and re-drill, or leave the inverter bolted in place and inhibit it — and the warning that the rail cannot be opened until power is off and a meter says the bus is down

Removing an Axis From a Running Kinetix 5700 System Without Faulting the Rest A 2198-D032-ERS4 is two axes behind one Ethernet connection on one set of bus bars, and inhibiting either half takes the other half with it. Getting the module off the rail is a different order of problem: control power and mains off, … Read more

Adding an Axis to a Kinetix 5700 System: the Module, the Axis, and the Four Places to Set It

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The Logix Designer controller organiser with a new 2198-D032-ERS4 named Drv_04 under the Ethernet bridge alongside a 2198-P208 and a 2198-S160-ERS4, and beneath it a motion group named Line_MG holding Axis_01 plus two new AXIS_CIP_DRIVE tags Axis_04A and Axis_04B, with a panel listing what the tree does not show: the bus sharing group, the half axis, ungrouped axes and the capacitance total

Adding an Axis to a Kinetix 5700 System: the Module, the Axis, and the Four Places to Set It The eighth axis on the line is a 2198-D032-ERS4 in the last 55 mm of the rail, and getting it into the project is four dialogs and about twenty minutes. What takes the rest of the … Read more

OPC UA Certificates: Trust, Rejection, and Why the First Handshake Fails

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The six stages of a first OPC UA connection drawn as boxes with numbered break points underneath: Hello and Acknowledge, the OpenSecureChannel request carrying the client certificate, the response carrying the server certificate, CreateSession, ActivateSession with the user token, and the first Browse or Read, with a different status code named at each break

OPC UA Certificates: Trust, Rejection, and Why the First Handshake Fails BadSecurityChecksFailed, status 0x80130000, is the answer an OPC UA server gives when it has decided not to talk to you and is not permitted to say why. Part 6 of the specification is explicit about it: the Reason string in an abort message “shall … Read more

The Kinetix 5700 Power Rail: What Each Module Is, and the Order They Go In

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A Kinetix 5700 rail drawn left to right with seven modules: a 2198-P208 DC-bus power supply at 85 mm, a 2198-S160-ERS4 single-axis inverter at 100 mm, a 2198-S086-ERS4 at 85 mm, two dual-axis inverters and two accessory modules at 55 mm each, with the DC-bus link lengths marked above each joint and end caps at both ends

The Kinetix 5700 Power Rail: What Each Module Is, and the Order They Go In A 2198-D032-ERS4 is 55 mm wide, a 2198-S160-ERS4 is 100 mm, and the DC-bus link that joins one module to the next is a moulded part in a fixed length that arrives in the box with the module. There is … Read more

Safety Feedback on a Kinetix 5700: What SFX and the Safe Speed Functions Need From the Encoder

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The chain from encoder to safe speed function on a Kinetix 5700: cycles per revolution, the DSL or universal port with its interpolation, the motion safety instance, the safety input assembly, the SFX instruction and the safety instructions that use its outputs

Safety Feedback on a Kinetix 5700: What SFX and the Safe Speed Functions Need From the Encoder A VPL-B0631T-W gives 512 cycles per motor revolution and a VPC-Bxxxx-Q gives 4096. Put the wrong one of those two numbers into the Motion Safety instance and the drive catches you: the DSL diagnostics compare the configured resolution … Read more

The 1756-OBV8S Safety Output Card: What a Pulse Test Does to a Contactor

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Bipolar against sourcing on a 1756-OBV8S: a single P and M pair driving one contactor, a fixed sourcing pair driving two, and the ratings, currents and chassis rules underneath

The 1756-OBV8S Safety Output Card: What a Pulse Test Does to a Contactor Point 3 of a 1756-OBV8S flashes red while its output is off, and the contactor it drives is behaving perfectly. That is no-load detection, and it is telling you the truth: something between OUT3-P and the coil has come apart. The detection … Read more

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