General Purpose
Sensor Transmitter Module
STM 31x / STM 31xC
The extremely power saving RF transmitter
module STM 31x of EnOcean enables the
realization of a wide range of wireless and
maintenance free sensors such as temperature sensors, humidity sensors, or room
operating panels.
Functional Principle
Power supply is provided by a small solar cell, an
external energy harvester, or an external 3V
battery. An energy storage element is installed to
bridge periods with no supply from the energy
harvester. The module provides a user configurable cyclic wake up. After wake up a radio telegram will be transmitted in case of a change of
any digital input value compared to the last sending or in case of a significant change of measured
analogue values. In case of no relevant input
change a redundant retransmission signal is sent
after a user configurable number of wake-ups to
announce all current values. In addition a wake
up can be triggered externally. The firmware can
be configured. Customer specific firmware can be
developed using the Dolphin API.
Features Overview
Power supply
 STM 310/310C: including solar cell and whip
 STM 311/311C: including solar cell and helical
 STM 312/312C: including whip antenna but no
pre-installed solar cell
STM 310
STM 311
STM 312
STM 310C
STM 311C
STM 312C
Ordering Code
Pre-installed solar cell (except STM 312 / STM 312C)
2.1 V–5.0 V, 2.6 V needed for start-up
pre-installed whip or helical antenna
868.3 MHz (STM 31x) / 315.0 MHz (STM 31xC)
Radiated output power
STM 310, STM 312: +8 dBm (EIRP)
STM 310C, STM 312C: +92 dBµV/m
STM 311: +5 dBm (EIRP)
STM 311C: +92dBµV/myp. 2 dBm at antenna base
Data rate / Modulation type
125 kbps / ASK
Start-up time with empty energy storage
typ. <2.5 min @ 400 lux, 25°C
Initial operation time in darkness @25°C1
typ. 4 days, if energy storage fully charged
wake-up every 100 s, transmission every 1000 s on average
Input Channels
Teach-in button
Transmission indicator
Module dimensions
Operating temperature1
20 pin connector: 3x digital input, 3x analog input, 2x WAKE input
1x internal
1x LED
43 x 16 x 8 mm
-20 up to +60 °C
Full performance is achieved after several days of operation (up to two weeks) at good illumination level. Performance degrades over life time, especially if energy storage is exposed to higher temperatures. Each 10 K drop
in temperature doubles the expected life span.
© EnOcean |
Subject to modifications | April 2013