Wiring temperature sensors - softwarecrash/Solar2MQTT GitHub Wiki

Wiring temperature sensors

Solar2MQTT supports DS18B20 temperature sensors.

Default pin mapping by build target

Build target	DS18B20 data	Note
`wemos_d1_mini32`	`GPIO21`	`D2` on the D1 Mini style layout
`esp32c3_supermini`	`GPIO3`
`esp32s3_supermini`	`GPIO6`
`waveshare_esp32_s3_eth`	`GPIO21`

The DS18B20 pin can also be changed later in the Web UI under Device Settings.

Set the pin to -1 if you want to disable the DS18B20 bus completely.

Standard one-wire wiring

DS18B20 VCC -> 3.3V
DS18B20 GND -> GND
DS18B20 DATA -> selected DS18B20 data pin
add a 4.7k pull-up resistor between DATA and 3.3V

Multiple DS18B20 sensors can share the same wire.

Maximum number of sensors

The current firmware supports up to 15 DS18B20 sensors on one 1-Wire bus.

In practice the reliable number also depends on wiring quality, cable length, pull-up resistor and power supply.

Sensor numbering

Sensors are published as:

DS18B20_1
DS18B20_2
DS18B20_3
...

The numbering is usually stable as long as the same sensors stay connected.

Where the values appear

MQTT topic <baseTopic>/LiveData/DS18B20_<n>
Home Assistant discovery if enabled

Notes

If a sensor is removed, its value disappears again after a short time.
If no sensors are found, no temperature values are shown.

If something does not work, start with wiring, settings and the Debug page.

Solar2MQTT is a community project. Some devices work immediately, others need a little troubleshooting and a good debug report.

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