Environmental sensor

HomeMatic-compatible temperature/humidity sensor

Environment sensor PCB PCB mounted in a project box, with AA-sized lithium battery

What is it?

A cheap, low-cost HomeMatic-compatible temperature & humidity sensor.
The design is optimized for automated assembly and does not need any manual (re-)work.

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

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)