Low-Cost Gateway For Non-Network PLC

Abstract

—Traditionally, data gathered from industrial sensors are transmitted from PLC to related operator
interfaces such as SCADA which enables monitoring and control. Even though operators can monitor data
remotely, but it always limits the number of users to operate it due to high cost. Thus, this project is to
develop a cost-effective integration of PLC to cloud-based system that enables to monitor data remotely.
However, 90% of the existing PLC in industry is a non-network device which leads difficulties to connect
PLC directly to cloud. Therefore, a gateway is to be designed to enable PLC to communicate with cloud.
Raspberry Pi 4 is used as the gateway to host a python program which acquires data from a PLC. The
program supports to read and write data from OMRON CP1E and CP1L PLC using RS232C-to USB
connection and siemens s7 1200 using ethernet connection. As for the cloud system, Google Cloud Platform
(GCP) is used to host the website application. Relational Database is hosted on the same GCP which store
the selected data from the PLC. The gateway was able to perform well with a message rate of 2.5 messages
per minute.