The wide supply voltage range also means that you can allow for a significant voltage drop along the bus (e.g., when using a bus cable of considerable length). The maximum number of devices that can be connected to a main cable is 32, including the Master. A Modbus RS485 connects a Master device to one or more Slave devices. RS485 interface gives some more benefits compared to RS232: simplicity and the robustness for long distance transfer. The adapter was placed under the microscope, and we traced the data A & B lines from the plug to the RS485 chip on the PCB. Removing the WiFi adapter and connecting directly to the inverter's COM port resulted in no data again so we knew that there was something on the WiFi adapter enabling the data from the inverter. 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.
It has an EM112 Series Energy Meter fitted in the same box to monitor energy production and consumption of the inverter. This is connected to the fuse box and has a 16 amp RCBO to protect the circuit. The circuit uses optical isolation (opto-coupler) to isolate your RS232 port from the RS485 cables. The RS232-RS485 adapter circuit diagram is show below, RS232 DB9 is used as the RS232 port, while only a terminal block is used as RS485 connector. You can easily connect more devices by splitting the cable at one connector and adding another cable to it. From openHAB, you can only see TCP "not working" and cannot even tell which area to look more closely at. If a serial transaction messes up, this gateway cannot tell you about it, and just fails the TCP transaction. TCP section - reduce your connect/disconnect overheads by settings in the Modbus binding. The gateway has limited processing power divided amongst several tasks, and Modbus binding default settings can hammer it. Henceforth, we shall consider Slave devices to be measuring instruments with serial communication, even if the cabling is similar for all Modbus devices.
The probes communicate using the standard Modbus RTU protocol. 00-3) or standard 12V power supplies. To get the solar PV power from the roof down to the basement shed, we purchased 20 meters of 6mm armoured cable; this was routed down the back of the house and into the shed through the stone wall. In reality, you can "usually get away with" one for short wiring runs, or even none for very short. 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. Figure 1 shows an example of a correct Bus connection. Normally, this connection is made at one end of the main cable. The shielding should be connected to earth at only one end. The end resistance must be used only at the ends of the main cable. It’s not so critical what cable exactly at reasonable lengths, but cat5 is ideal.
For example, Belden 3105A cable can be specified, but different types of cable with equivalent characteristics can be used. This can be fatal to your PC or controller. If your PC or controller only has RS232 port then you need an RS232 to RS485 converter or adapter for your PC or controller. RS485 lines need bias resistors as well - weak resistors that apply a voltage to the line representing a clean "idle" state. The diagram below shows a basic RS485 cable for use with the RJ11 socket on Unitronics PLCs. 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.
The War Against Rs485 Cable
by Alecia Larcombe (2024-07-06)
The wide supply voltage range also means that you can allow for a significant voltage drop along the bus (e.g., when using a bus cable of considerable length). The maximum number of devices that can be connected to a main cable is 32, including the Master. A Modbus RS485 connects a Master device to one or more Slave devices. RS485 interface gives some more benefits compared to RS232: simplicity and the robustness for long distance transfer. The adapter was placed under the microscope, and we traced the data A & B lines from the plug to the RS485 chip on the PCB. Removing the WiFi adapter and connecting directly to the inverter's COM port resulted in no data again so we knew that there was something on the WiFi adapter enabling the data from the inverter. 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.
It has an EM112 Series Energy Meter fitted in the same box to monitor energy production and consumption of the inverter. This is connected to the fuse box and has a 16 amp RCBO to protect the circuit. The circuit uses optical isolation (opto-coupler) to isolate your RS232 port from the RS485 cables. The RS232-RS485 adapter circuit diagram is show below, RS232 DB9 is used as the RS232 port, while only a terminal block is used as RS485 connector. You can easily connect more devices by splitting the cable at one connector and adding another cable to it. From openHAB, you can only see TCP "not working" and cannot even tell which area to look more closely at. If a serial transaction messes up, this gateway cannot tell you about it, and just fails the TCP transaction. TCP section - reduce your connect/disconnect overheads by settings in the Modbus binding. The gateway has limited processing power divided amongst several tasks, and Modbus binding default settings can hammer it. Henceforth, we shall consider Slave devices to be measuring instruments with serial communication, even if the cabling is similar for all Modbus devices.
The probes communicate using the standard Modbus RTU protocol. 00-3) or standard 12V power supplies. To get the solar PV power from the roof down to the basement shed, we purchased 20 meters of 6mm armoured cable; this was routed down the back of the house and into the shed through the stone wall. In reality, you can "usually get away with" one for short wiring runs, or even none for very short. 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. Figure 1 shows an example of a correct Bus connection. Normally, this connection is made at one end of the main cable. The shielding should be connected to earth at only one end. The end resistance must be used only at the ends of the main cable. It’s not so critical what cable exactly at reasonable lengths, but cat5 is ideal.
For example, Belden 3105A cable can be specified, but different types of cable with equivalent characteristics can be used. This can be fatal to your PC or controller. If your PC or controller only has RS232 port then you need an RS232 to RS485 converter or adapter for your PC or controller. RS485 lines need bias resistors as well - weak resistors that apply a voltage to the line representing a clean "idle" state. The diagram below shows a basic RS485 cable for use with the RJ11 socket on Unitronics PLCs. 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.