BadIdentityTokenRejected is the answer an OPC UA server gives when the secure channel is up, the client certificate is trusted, and the session request arrives with no user in it, and on an S7-1500 with guest authentication off that is exactly where a first Python OPC UA client stops. It is the third of four … Read more
K1 is a 110 V AC contactor on a saw, its coil is switched by a solid-state relay, the SSR is driven from output pair 0 of a 1791ES-IB8XOBV4, and every 600 ms the contactor makes a small tick you can hear from the door of the panel. The scope on O0+ shows why: the … Read more
A 1606-XLE240E Series B has a DC-OK relay on terminals 13 and 14 that closes while the 24 V bus is above 90 % of its set point, and a Raspberry Pi 4 needs 5.1 V and somewhere between five and twenty seconds of notice to halt without corrupting its card. Raspberry Pi panel power … Read more
The guard on the case packer closed at 14:07 and the infeed conveyor started on its own, with the blue reset button 4 m away and nobody within reach of it. The DCS instruction on that gate was configured Restart Type Manual, exactly as the drawing said, and the machine still restarted, because the button … Read more
A Node-RED Logix tag read takes one install script, one palette install and two dialogs on a Raspberry Pi 4: Zone7_Speed from a 5069-L306ER appears in the debug sidebar as 30.0, and none of it involves typing a line of code. The node that does it is node-red-contrib-cip-ethernet-ip 1.1.3, installed from the palette manager, configured … Read more
K1 and K2 are 100S-C09 safety contactors in series on a 4 kW conveyor motor, the CROUT that drives them holds Fault Code 16#5003 – both feedbacks ON with the outputs off – through every press of the reset button, and the suggestion at 06:10 was to raise the Feedback Reaction Time from 100 ms … Read more
At 02:30 on Sunday 25 October 2026 a logger in Berlin writes a row, and sixty minutes later it writes another row stamped 02:30, and the trend viewer draws the second hour on top of the first. Meanwhile the controller it reads from keeps its own idea of the time as a LINT of microseconds … Read more
A pusher divert with its trigger eye 1.20 m upstream and a 2780 ms delay in the program was diverting 97% of the 600 mm cartons and 61% of the 300 mm totes, and every tote it missed was hit on its back corner and spun onto the takeaway sideways. The 2780 ms was right … Read more
48,000 rows is what a Raspberry Pi reading 20 tags a second has to hold through a 40-minute outage, and the SQLite file that held them in the run behind this article was 5.3 MB, including the write-ahead log. That is the size of the buffering PLC data problem, and it is small. What is … Read more
Two cartons released 1.1 seconds apart from line A and line B arrive at a 30 degree merge at the same moment, because line A’s release eye is 1.3 m from the junction and line B’s is 1.7 m, and 0.4 m at 0.28 m/s is 1.4 seconds. The rung that let that happen was … Read more
read_holding_registers(40011, count=2) comes back with exception code 02, read_holding_registers(11, count=2) decodes to -2.4e-41, and the 230.5 V the meter shows on its own display is sitting at address 10. That is the Modbus TCP register offset, and it is the fault everybody hits on their first evening with pymodbus 3.15.0 and a power meter on … Read more
A 42EF retroreflective eye bolted 150 mm back from the discharge roller of a 1.5 m zone stops a 600 mm carton with 750 mm of zone still behind it, and stops a 1219 mm carton with 131 mm. Move the same eye to 50 mm from the discharge and the first carton overshoots into … Read more