1 Wire Bus experience

Projects Networking, Protocols, and Devices
1

Hello,

I created a 1 wire bus (length about 100m Cat7 cable) with 9x DS18b20 temperature sensors. When I tested the sketch, I couldn't reach any sensor.
Than I did the following things:

  • I removed the first half of the sensors -> without any change in the sketch these sensors were reachable
  • I reconnected the first half and disconnected the second half -> second half of the sensors were reachable

After that, I cutted the cable in the middle and created two different 1wire networks (one at output 3, one at output 4). The result was unchanged: the first bus worked, the second bus worked- but if I connected both busses (one to output 3, one to output 4) no device is reachable.

Is there a limitation regarding the amount of sensors inside Arduino?
I'm using the 3.3V plug on my ArduinoEthernet. Is there a current limitation?

Thanks
Tobias

2

I'm using the 3.3V plug on my ArduinoEthernet. Is there a current limitation?

Yes there is always a current limitation on any supply. Measure the voltage under load to see if it is sagging and causing you a problem.

Is there a limitation regarding the amount of sensors inside Arduino?

Yes again there always is because the Arduino like any other processor has a limited memory capability.

Have you read:-
http://playground.arduino.cc/Learning/OneWire

3

When I tested the sketch

What sketch?

Pete

4

Solved, I added a new pull up resistor 10k (between data and 3.3V) at all sensors

Thank you