PQMII-T20 Computer Controller

Unlike most fieldbuses (e.g. Profibus, CC-Link, etc.) that use RS485 master-slave protocol for the physical layer, CAN’s media access uses carrier-sniffing multiplexed access (CSMA) technology, which allows for a multi-master mode of operation. And, due to the use of non-destructive bus arbitration technology, bus conflict arbitration time is greatly saved.

Unlike most fieldbuses, the PQMII-T20 CAN bus has only physical and data link layers, leaving the application layer to be developed by the user, giving the user considerable flexibility. These advantages are so compelling that some well-known fieldbuses (e.g. DeviceNet, CANopen, etc.) use CAN as their underlying layer, and many programmable controller manufacturers offer CAN communication card options or CAN bus interfaces.

The core of PQMII-T20 is a Berger programmable computer controller (Programmable Computer Controller abbreviated as PCC) BR2005, which is connected to the touch screen monitoring station (Provit2200) through the 422 bus, where the operator enters the commands and monitors the running status of the whole machine. The PCC is connected to 29 Siemens inverters via CAN bus, and uses the CAN bus to transmit frequency setting commands, start and stop the inverters, and monitor the operating status of the inverters. 29 inverter motors are synchronised by the elastic frame, which is not shown in the figure. the PCC also completes the logic control of the whole machine and the closed-loop control of the temperature, pressure, flow rate, liquid level, PH value and recipe.