RS485 Cable Replacement, no Modbus? > 자유게시판

This UART-RS485 Converter module has an on-board MAX485 chip which is a low-power and slew-rate-limited transceiver used for RS-485 communication. It works on half-duplex communication to implement the function of converting the TTL level into RS-485 level which means it can either transmit or receive at any time, not both, it can achieve a maximum transmission rate of 2.5Mbps. MAX485 transceiver draws a supply current of between 120μA and 500μA under the unloaded or fully loaded conditions when the driver is disabled. Most of the low-cost sensors and other modules like GPS, Bluetooth, RFID, ESP8266, etc. which are commonly used with Arduino, Raspberry Pi in the market uses UART TTL based communication because it only requires 2 wires TX(Transmitter) and RX (Receiver). We have been using Microcontroller Development Boards like Arduino, Raspberry Pi, NodeMCU, ESP8266, MSP430, etc. for a long time now in our small projects where most of the times distance between the sensors and board is not more than few centimeters at max and at these distances, the communication between the different sensor modules, relays, actuators, and controllers can be easily done over simple jumper wires without us being worried about the signal distortion in the medium and the Electrical noises creeping into it.

At small transmission distances speeds up to 35Mbps can be realized with RS485 although the transmission speed will decrease with distance. At 1200m of transmission speed, you can use only 100kbps of transmission speed. It also has onboard LEDs to display the current state of the chip i.e. whether the chip is powered or its transmitting or receiving data making it easier to debug and use. So, in the Arduino code, we will focus on sending the data and display that sent or received data on the LCD screen. TXSoil can transmit the humidity to a Web server or to a VisualVision’s display / concentrator such as DisplayRX or ControlHUB or RXTXeasy GSM - with adjustable interval, remaining for the rest of the time in standby with very low consumption. When full-duplex is converted into half-duplex only one device at a time can transmit data. As it is a half-duplex IC hence it cannot both transmit and receive at the same time. RS-485 supports inexpensive local networks and multidrop communications links, using the same differential signaling over twisted pair as RS-422. Automatic Converters take care of the timing problems and allow fast communications without software intervention. Several volts difference in the ground level of the RS485 transmitter and receiver does not cause any problems.

The RS485 receiver compares the voltage difference between both lines, instead of the absolute voltage level on a signal line. It operates on a differential signaling method of measurement rather than voltage measurement wrt GND pin. Signal High and Lows are measured against the GND level so shifting the GND level will have a disastrous effect on the data transfer. Sig- lines are twisted as twisting nullify the effect of electromagnetic noise induced in a cable and provide a much better immunity against the noise which allows the RS485 to transmit the data up to 1200m of range. But if you are building a control system with these development boards over a distance greater than 10 to 15 meters, then you should take the noise and signal power into consideration because if you want your system to work reliably, then you cannot afford to lose the data while transferring. I want to talk with.

There are many categories of Ethernet cables we can use like CAT-4, CAT-5, CAT-5E, CAT-6, CAT-6A, etc. In our tutorial, we are going to use CAT-6E cable which has 4 twisted pairs of 24AWG wires and can support up to 600MHz. It is terminated at both ends by an RJ45 connector. In this tutorial, we are going to learn about the RS485 communication protocol and how to implement it with the two Arduino Nano we have with us and how to use the MAX485 RS485 to UART conversion Module. Nowadays, we mostly use Wi-Fi for internet connectivity but earlier we used to use Ethernet cables going to each personal computer to connect it to the internet. There are many different types of serial communication protocols like I2C and SPI which can be easily implemented with Arduino and today we are going to look at another most commonly used protocol called RS485 which is very commonly used in high noise industrial environments to transfer the data over a long distance. We will send some data from the transmitter side over the cable from the Nano which is converted to RS485 signals via MAX RS485 Module working in Master Mode.

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