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Our plans to upgrade our solar PV system this year are slowly progressing with installing a new Solis 1.5kW inverter and an EM112 Series Energy Meter, which have RS485 output and communicate using Modbus protocol. Using the Solis Data Logging Stick, which uses WiFi to communicate, we were able to set up the inverter to send data to the remote soliscloud service, but we could not find any way to get capture data apart from scraping the basic status page built into the WiFi adapter which only gave watts being produced and daily output. RS485 is simpler because it uses only two wire (or a single pair) to carry out the data in bidirectional manner, using RS232, we need 3 wires at minimum to carry the data bidirectionally. Two Tibbo Project System (TPS), Gen. 2-compatible Tibbo BASIC applications for the setup and testing of Bus Probes are available: BP-Tester-UI and BP-Tester-Web. The normal way to implement this is with a two wire system with differential signal levels. 5 should work in your situation because of the voltage you will be running (5-10V) and your signal is not high frequency (above 500Mhz) in the first place.

Control and monitoring systems: A single pair of rs485 signal cable can connect up to 32 devices, with a signal transmission distance of up to 1200m. Therefore, using rs485 cables is an ideal choice for industrial control and monitoring systems, especially those with large-scale and high dispersion. It consists of two insulated copper conductors twisted together, which helps reduce electromagnetic interference and ensures signal integrity. Two wire telephone cables will not function because in that case the ground signal levels on both sides will be floating. It specifies voltage levels, connector types, and signal functions. The Jazz PLC series from Unitronics are not standard equipped with a RJ11 connector for serial communications. RS232, RS485, and RS422 are recommended standards for serial communication. RS485 communication is well-suited for robust and noise-resistant data transfer applications, making it ideal for environments with electrical interference or long cable runs. Ideal solution for long distance RS485 communication with DC transmission ability , adapts tree network RS485, star network RS485 well. These cables are commonly used in industrial automation, building automation, and other applications where reliable and robust communication is necessary. Differential signals and twisting allows RS485 to communicate over much longer communication distances than achievable with RS232.

RS485 cable length can be as long as 1.2 km, while RS232 only about 25 meters. Bus Probes are a family of low-power environmental sensors with an RS485 interface. These signals are commonly called A and B in RS485 systems. The diagram below shows a basic RS485 cable for use with the RJ11 socket on Unitronics PLCs. The block diagram shows the transmitter uses an HT12E encoder, 555 timer, AND gate and IR LED to transmit switch states via infrared signals. RS485 uses two wires and sometimes a ground connection, so we used a twin-screen cable to go between the inverter to the EM112 Series Energy Meter and then onto the Raspberry Pi with a DB9 connector connected to the RS485 Pi board. Normally pin 7 (RTS) and pin 4 (DTR) are used on the DB9 connector. You can easily connect more devices by splitting the cable at one connector and adding another cable to it. The transmission speed of RS485 cables can vary depending on factors such as cable length, baud rate, and the quality of the cable itself.

Device parameter adjustments and data transfer via the RS485 connection. With the Solis inverter connected to the Raspberry Pi, we were initially unable to communicate with the inverter, and the Python scripts returned connection errors. If we want to connect a PC with an Unitronics PLC, for example for programming or debugging reasons, we need a connection cable which is on one side fitted with a female DB9 connector, and on the other side with an RJ11 jack. We will describe the steps to run the Python example in this section. Be sure to keep "Add Python to environment variables" checked, and click "Browse" to modify the installation address. First, download the latest installation package from the Python website. The USB cable requires a specific programming package and does not support freeport communications. This command can be used to install the package in this project, and you can see the package to be used only is "pyserial" and has been installed.