Shelly Plus 1PM+ADD-ON Plus+3xTemperature Sensor DS18B20 doesn't work

Stanislav Jane · Screenshot 2023-10-01 at 10.48.59.png

Hello,

I installed new Shelly 1PM Plus with Shelly ADD-ON Plus. Connected 3x temperature sensors DS18B20, but have problem, that 3rd sensor can't be found and add.

If I connect one or two sensors, then it work, but when I want add 3rd, then 3rd is not found. I tested all 3 sensors one by one and all 3 works normally. I tested also connect any combination 2 from 3 sensors and each couple also works. Each sensor is connected separately to top connector line - se attached wiring image.

Firmware is latest available, all work normally, but only problem is with visibility of 3rd temperature sensor.

Do you have any advice or tip how to solve this problem?

NisseH

How long are the cables to the sensors ? I have more than 20 DS18B20 with up to 20 meter cables BUT you cannot connect more than one long sensor cable (for each input). The others must be short. If you check the application notes for DS18B20 you will find this limitation. This is because the delays will be too long for some signals.

Try to connect three sensors with short cables. "Short" is certainly less than 1 meter.

AN148: GUIDELINES FOR RELIABLE LONG LINE 1-WIRE NETWORKS