No temperature reading from onboard DS18B20


I have recently purchased the MQTT relay and setup the Wifi. All connectivity and NTP is working fine. I can control the relay via the web interface.

At first the unit would not connect to my MQTT broker (running on emonpi) so I couldn’t set/get the relay value via MQTT. I have flashed the firmware to v3190 and the MQTT integration is now working

However the onboard DB18B20 does not seem to be working (either before or after the firmware upgrade). The thermostat control page shows NaN and no temperature values are reported via MQTT.

I have enabled the DB18B20 and tried all of the “pin” settings but to no avail.

I see someone else had a similar problem here : No reading on DS18B20 on WiFi MQTT relay

Any ideas?


You need an external 1820 sensor ?

The WiFi relay does not have an on-board temperature sensor, you need to connect an external sensor.

The blurb on the shop page says

“Temperature sensor support - 1 x sensor included”

And the documentation says

"2. Thermostat Scheduler

Heating or A/C schedule and desired set point (from connected internal DS18B20 temperature sensor) can be set using the Thermostat Scheduler interface"


All WiFi MQTT relays bought from the shop should come with an external temperature sensor supplied (but not fitted).

If you have not received one, we will get one sent out to you.

I think Brian’s point was the description here appears to be inaccurate:

It was a question. Either the description was wrong, or one wasn’t sent.

Seems it was the latter.

@spiderlane, email the shop and one will be sent out I am sure.