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
Wireless PLC communication done properly: choosing Wi-Fi, 900 MHz radios or cellular, RPI and timeout budgets, antennas, roaming, and link loss logic.
Modbus TCP, EtherNet/IP, PROFINET, OPC UA and MQTT compared by how they move data, with ports, poll rates and the mistakes that cost SCADA update time.
Wire a power meter into Logix or S7, totalize kWh in Structured Text, hold the demand peak with priority load shedding, and check if a VFD retrofit pays.
SunSpec Modbus inverter limits, tracker stow, wind turbine pitch and yaw, a battery SoC window with BMS handshake, and curtailment setpoints over DNP3.
Where the PLC stops and the relay starts, a generator start permissive rung, the synchronising handshake, load shed stages and switchgear interlocks.
Zones and conduits, the controller key switch, FactoryTalk Security, firewall rules for 44818 and 502, and a backup you have actually restored.
How a packaged skid PLC gets tied into DeltaV, Experion or PCS 7: link protocol, Modbus register map, heartbeat, engineering units and alarm ownership.