Hi,

I need to connect 12 ds18b20 temperature sensors to a Metrawatt Smartcontrol system. Instead of using the build-in temperature sensor connections, I have to connect them using MODBUS and the available RS485 connectors on the device. I've figured out how to connect 12 together, which is easy enough, but I can't for the life of me figure out to what connector I have to connect the "DQ" wire to. I can choose between Tx+, Tx-, Rx+, Rx-, A, B, Y, Z

I found some annectdotal clues that I need to connect it to Tx+, but also to maybe short tx and rx together...

Does anyone know the right answer?
Thanks.

 

Are the DS18B20 temperature sensors on one 1-Wire cluster?
What is the maximum distance between the first and last sensor?
What is the length of the RS-485 connection to the Metrawatt Smartcontrol?

The only solution I have to offer consists of an RS-485 transceiver interfaced to a microcontroller connected to the 1-Wire network.

 

Hi MrChips

The sensors are one-wire. The maximum distance between sensor 1 and 12 will be between 7 and 10 meters I suspect. The RS485 connector to the Smartcontrol is approximately 10-12 metres. I have to pick up the sensors in a few hours. Supposedly there's a "converter" in the order too. I'll post back later. Thank you for your help.

 

Alright the devices are in. There's a one-wire to MODBUS RTU converter here too so that's good. I'm left to wonder if RTU is compatible with regular MODBUS: can MODBUS devices be hooked up to the same rs485 port as the RTU device?

 

Hi MrChips

The sensors are one-wire. The maximum distance between sensor 1 and 12 will be between 7 and 10 meters I suspect. The RS485 connector to the Smartcontrol is approximately 10-12 metres. I have to pick up the sensors in a few hours. Supposedly there's a "converter" in the order too. I'll post back later. Thank you for your help.

With this converter http://cel-mar.pl/files/io/io_ada-401wa_en.pdf they are using Tx- (see 3.4.CONNECTION TO 1-WIRE NETWORK) I would think that the "converter" might have something definitive for you - no?