RMPS and RLIM on a ControlLogix: Ramping a Setpoint Instead of Stepping It A sequence step writes 75.0 into the speed reference of a PowerFlex on a packing line that was sitting at 20.0, and the drive comes back with an overcurrent on acceleration about 400 ms later. Nothing in the controller did anything wrong. … Read more
A SCADA client stores one string for every value it reads, and on the line I am about to describe that string is CLX_Line1.Bagger.Infeed.Belt1_Run. Four names, each chosen by a different person on a different day, and 684 more strings on that one device built the same way. Rename the tag group on a Friday … Read more
TON, TOF and RTO on a ControlLogix: What Each One Does When the Rung Goes False The prescan row for a TOF in 1756-RM018A sets .ACC equal to .PRE. Not to zero, the way a TON’s does — to the preset, which is the value that means the timer has already finished, so the first … Read more
SQO and SQI on a ControlLogix: the Sequencer That Will Not Step SeqCtl.POS sat at 1 for three days on a 1756-L83E while the indexer kept running on step one, and the rung holding the SQO had nothing in it at all — left rail, instruction, right rail. That is the entire fault, and the … Read more
JSR, SBR and RET: Passing Parameters Into a Routine Without a Controller Tag Type 4, Code 31 on a 1756-L83E, and the routine it pointed at was three rungs long. The general instructions reference gives three separate ways to earn that code and every one of them is about counting: a JSR with fewer input … Read more
FAL and FSC Over an Array: the Control Tag, the Position and the Scan It Takes An FSC with a Length of 10 found its mismatch at element 3 on a 1756-L83E and then stopped looking. .FD was 1, .POS was 3, .IN was 1, and elements 4 through 9 were never compared — not … Read more
The MSG Control Tag on a Logix Controller: What Each Tab Writes Into It Line_Msg.DN came true on rung 13 of a 1756-L71 and the forty DINTs the rung was guarding still held last shift’s numbers. The bit had been set by a different message — a four-element write to a capper down on rung … Read more
COP and CPS Instructions on a ControlLogix: Which One Copies What A COP with a Length of 20 moved five bytes. The source was Packer_Raw, a SINT[5]; the destination was Packer_Scaled, a DINT[10]; the rung went true on every scan of a 1756-L71 and nothing faulted, nothing latched, nothing appeared in the Minor Faults tab. … Read more
The scope says twelve bays, a MiCOM C264 in each cubicle, a gateway to the control centre, and an SCD file that the protection engineer will issue in week six. There is no ladder anywhere in it, no tag database you recognise, and no download button of the kind you have been pressing for fifteen … Read more
The numeric display is assigned {::[CLGX]Program:Packer.Bag_Count}, the value counts up all afternoon while the application is tested on a laptop, and the PanelView Plus 7 bolted to the machine shows four dashes. The tag is not the problem. The shortcut called CLGX carries two communication paths that are configured in two different places, and the … Read more
A new SM 1223 goes into slot 2, the panel comes back up, and the ERROR LED flashes red while the STOP/RUN LED sits solid yellow. The module that came out was 6ES7223-1BL32-0XB0. The one from stores is 6ES7223-1BL32-1XB0, and those two part numbers are the same sixteen inputs and sixteen outputs in the same … Read more
FB120 carries the orange half-circle in the project tree and the block you have open is the one you wrote on Tuesday. On an S7-1500 that symbol is the result of a checksum comparison, not a time stamp comparison, and the manual lists more than a dozen separate checksums behind it. Three of them have … Read more