Interfacing Humidity & Temprature sensor using RS485

[liono]

Hi,

I am having a H&T sensor with RS485 interface.
The website is useless regarding the documentation.

Any idea how to interface this device with Windows and Linux system?

The webpage for the product is here:
**broken link removed**

Thanks.

 

[barry]

I think you need to contact the company. You're right, there is no information there.

 

[shaiko]

You're right, there is no information thereu're right, there is no information there

Well...there's something.
The page suggest that the temperature sensing element is: DS18B20

Google suggests that this IC has a 1 wire interface - nothing about RS485.

lion, what type of connector do you see on your device?

 

[ALERTLINKS]

**broken link removed**

 

[FvM]

A clear and well understandable product documentation. The sensor is using industry standard MODBUS RTU protocol.

 

[liono]

Thank you all for the help. Appreciated.

I am a newbie in the field, however, I do not see in the manual how to send the device a command so that it returns the H&T values.

The use of function code is not clear in the manual, also the it is not shown what are the Temperature and Humidity registers.

My Question:
How to poll this device to read the H&T registers.

Thanks

 

[FvM]

The use of function code is not clear in the manual, also the it is not shown what are the Temperature and Humidity registers.

The problem is that you're apparently not familiar with MODBUS. The example given in the manual reads two registers starting with register 0, using function code 3 Read Holding Registers. It's not said if single register read of register 0 or 1 also works, probably yes. But the example should be sufficient to operate the sensor.

For MODBUS protocol details, visit https://www.modbus.org/tech.php.

 

[liono]

Thank you FvM.

You are right , i have little info when it comes to ModBus.

Thanks for the link.

 

[ahsan_i_h]

My Question:
How to poll this device to read the H&T registers.

Using SCADA software with modbus RTU (master) protocol enabled, you can read H&T registers. There are many free version of SCADA softwares with limited tags. As you only need two tags (H&T), so you can start with free version of "modbus SCADA" from http://www.wlcsystems.com This software only supports modbus protocol and free version is fully functional upto three tags.

Besides you also need a USB(or RS232) to RS485 converter.

 

[liono]

Thank you ahsan, the idea is to create my own interfacing code. I got the RS232 <--> RS485 converter.

Thank you for the tip though.