RS485 Wind Direction Sensor/Transmitter Wiki

Introduction

The wind direction sensor is a professional meteorological instrument used to measure horizontal wind direction. It integrates a hall sensor inside. The shell and weather vane are made of aluminum alloy material and use special mold precision die casting process, featuring small dimension tolerance and high surface accuracy. The sensor internal circuit is protected, which makes the sensor have the properties of high strength, weather resistance, anti-corrosion, and waterproof. The cable connector adopts corrosion-resistant military plug that ensures the long service life of the product.
A low-inertia wind vane is used to sense the wind direction. When the wind direction changes, the tail wing rotates to drive the axle magnet to rotate through the shaft, thereby obtaining accurate wind direction information. It can detect the 16 natural wind directions. This sensor with high cost performance can be widely used in meteorology, ocean, environment, airports, ports, laboratories, industry, agriculture and transportation.

Features

High measurement accuracy, fast response, good interchangeability
Easy to install and operate
High sensitivity: start-up wind speed ≤ 0.3m/s
Suitable for various harsh environments, strong wind resistance

Specification

Measuring Range: 16 directions
Start-up Wind Speed: 0.3m/s
Lead Length: 2.5m
Power Voltage: 7-24V
Communication Protocol: RS485 interface Modbus protocol

Dimension

User Guide

1. Wire Color Description

Color	Function
Red	Positive
Black	Negative
Yellow	RS485+/A/T+
Green	RS485-/B/T-

2. Installation Instruction

The white dot on the sensor must face true north in installation.

3. Modbus Protocol

The default communication parameters are: baud rate 9600bps, one start bit, 8 data bits, no parity, and one stop bit.
Modbus Register

Parameter	Register Add.	Function Type	Function No.	Parameter Range & Description	Default Value
Wind Direction Value	0x0000	INT16 RO	0x03/reading	0-15	None
Modbus Slave Address	0x1000	INT16 reading-and-writing	0x03/reading 0x10/writing	0-255	2

Modbus Register Parameter Instruction

Wind Direction Value
Parameter Range	0-15	Default Value: none
Parameter Storage	None

Indication: wind direction value
Example: If the returned value is 00 04 (hexadecimal, true form), the high byte of the first byte is 00, the low byte of the second byte is 04, and the measured wind direction value is (00*256+04)=4, 0 for true north and clockwise 4 for true east.

Modbus Slave Add. (ADDRESS)
Parameter Range	0-255	Default Value: 2
Parameter Storage	Immediate storage

Modbus address can be set to 0-255. You can use 0 address to set any address.

Example

Read register 0x0000, also wind direction value

Host query frame (hexadecimal): 02 03 00 00 00 01 84 39 (8byt)

Slave Add.	Function Code	Register Start Add.	Length of Register	High Bits of Check Code	Low Bits of Check Code
1byt	1byt	2byt	2byt	1byt	1byt
0x02	0x03	0x00 0x00	0x00 0x01	0x84	0x39

Slave response frame (hexadecimal): 02 03 02 00 03 BC 45 (7byt)

Slave Add.	Function Code	Number of Valid Bytes	Data Aera	High Bits of Check Code	Low Bits of Check Code
1byt	1byt	1byt	2byt	1byt	1byt
0×02	0x03	0x02	0x00 0x03	0xBC	0x45

16 directions value = 00 03 = 3, the direction is east-northeast according to the table below.

Correspondence Table

Value	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
Direction	North	Northeast by north	Northeast	Northeast by east	East	Southeast by east	Southeast	Southeast by south	South	Southwest by south	Southwest	Southwest by west	West	Northwest by west	Northwest	Northwest by north

Change register 0x1000, i.e. change Modbus slave address (ADDRESS)

Change Modbus slave address to 03

Host query frame (hexadecimal): 00 10 10 00 00 01 02 00 03 FA 00 (11byt)

Slave Add.	Function Code	Register Start Add.	Length of Register	Number of Valid Bytes	Slave Add. to Be Written	High Bits of Check Code	Low Bits of Check Code
1byt	1byt	2byt	2byt	1byt	2byt	1byt	1byt
0x00	0x10	0x10 0x00	0x00 0x01	0x02	0x00 0x03	FA	00

Slave response frame (hexadecimal): 00 10 10 00 00 01 04 D8 (7byt), and that indicates the modification is successful.

Tutorial on Raspberry Pi

1. Connection

Here USB to RS485 Module is used.

2. Install libraries and download routines

Type the following commands in the terminal one by one

cd /tmp        
wget https://project-downloads.drogon.net/wiringpi-latest.deb   //Download wiringpi library        
sudo dpkg -i wiringpi-latest.deb  //Install wiringpi library        
cd .....                                                     //Enter the content you want to save file in        
git clone https://github.com/DFRobotdl/RS485_Wind_Direction_Transmitter.git     //Download program in github        
cd RS485_Wind_Direction_Transmitter/

3. API Function List

/**
  @brief  initialize serial port
  @param  device Address of serial port，In Linux, it is the directory where the device is located.
  @return  Return 1 for initialization failure, and return 0 for initialization success
*/
unsigned char Init(char *device);

/**
  @brief  Modify address
  @param  Address1 For the current address, you can set any address with 0 address
  @param  Address2 The modified address.
  @return  A return value of 1 indicates success, and a return value of 0 indicates failure
*/
unsigned char ModifyAddress(unsigned char Address1, unsigned char Address2);

/**
  @brief  Read wind direction
  @param  Address The address where you want to read the data
  @return  The return value ≥0 indicates successful reading, the return value is the wind direction corresponding to the following table, and the return value is -1 indicates failed reading
                                                           Return the value to the direction correspondence table
  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  |   value   |   0   |     1     |     2     |     3     |  4   |     5     |     6     |     7     |   8   |     9     |     10    |     11    |  12  |    13     |     14    |     15    |
  |-----------|-------|-----------|-----------|-----------|------|-----------|-----------|-----------|-------|-----------|-----------|-----------|------|-----------|-----------|-----------|
  | Direction | North | Northeast | Northeast | Northeast | East | Southeast | Southeast | Southeast | South | Southwest | Southwest | Southwest | West | Northwest | Northwest | Northwest | 
  |           |       | by north  |           |  by east  |      |  by east  |           | by south  |       | by south  |           |  by west  |      |  by west  |           | by north  |
  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

*/
int readWindDirection(unsigned char Address);

4. Check the device

Type this in the terminal:

sudo ls -l /dev

Find out the device you just connected in.

5. Open the previously downloaded min.c file, change the device port in the program to the actual one and save it

6. Use the terminal to open the folder where the program is located, compile and run

gcc -Wall -lwiringPi -o Wind_Direction *.c
sudo ./Wind_Direction

You can see the accurate wind direction information

FAQ

For any questions, advice or cool ideas to share, please visit the DFRobot Forum.

RS485 Wind Direction Sensor/Transmitter Wiki - DFRobot