HomeBrew environment sensor

published 24.01.2020

RevB HB sensor

Technical specs:
— HomeMatic-compatible sensor
— Input voltage: 3V (2x AA or 1x LS14500 lithium recommended)
— Absolute maximum input voltage: 3.6V (don't use LiIon or LiPo cells!)
— Low idle/quiescence current: 3.2µA
Very long battery life (> 3 years)
— Measurement every ~3 minutes
— Accuracy: Humidity: ±2.0 %RH, Temperature: ±0.3 °C
— Using ATmega328 (MCU), CC1101 (TRX), SHT21 (Sensor)
— Optional BMP280 pressure sensor
— Optional SMA footprint for external antenna
Extension header (UART, I2C, 1 GPIO)
Firmware updates via OTA
— Running AskSin++ firmware

This design is optimized for machine assembly at JLCPCB.


Operating modes:
There are several different operating modes which determine the sensor behaviour.
Some add additional features and need a CCU addon to be compatible.

WDS40 mode
This mode emulates a stock HM-WDS40-TH-I-2 sensor and is usable without any addons.

Temperature and Humidity
This mode provides the HB-Sen-Temp-I sensor type. It additionally reports battery voltage.

Temperature, Humidity and Pressure
This mode provides the HB-Sen-Env-I sensor type. It reports battery voltage and pressure.
(Requires BMP280 sensor to be populated)

CCU interface

To pair a new sensor, put the CCU in pairing mode and short push the button once.
After the LEDs stop blinking, the device can be found in the web interface.
To reset the pairing hold the button for ~10 seconds until it stops blinking. It can then be paired with a short push.