The emonTH is an open-source, battery powered, Temperature and Humidity monitoring wireless node.
It's been designed to be an easy to deploy tool for monitoring building / room temperature and humidity.
The data from the emonTH is transmitted via wireless (433/868Mhz) to an emonBase web-connected base-station (we recommend a Raspberry Pi with an RFM12Pi) which then posts the data onto an emoncms server (e.g. emoncms.org) for logging, processing and graphing. The room temperature and humidity data can be used to inform a heating control system, feed into a building performance model or simply for general interest!
Temperature and Humdity sensing options - Using DHT22 temperature and humidity sensor, or if humidity is not required just a DS18B20 temperature sensor.
Easy to set-up - the unit comes pre-assembled and pre-loaded with Arduino compatible firmware. If desired the code can easily be changed by using an USB to UART cable and the Arduino IDE to upload a sketch of your choice onto the on-board ATmega328 microprocessor.
Long Battery Life - The emonTH is powered by two AA batteries through a high efficiency DC-DC boost converter circuit, taking a reading once every 60s the emonTH batteries should last for 1-3 years. We recommend rechargeable alkaline batteries for best performance and environmental impact (see blog post).
Expansion Options - If desired the emonTH function can easily be expanded: remote DS18B20 temperature sensors can be screwed into the terminal block for outdoor temperature monitoring, multiple DS18B20 temperature sensors can be connected at once on a digital one-wire bus.
An optical sensor can be added for interfacing with a pulse-output utility meter or a relay board could be connected for controlling an appliance.
Flexible choice of RF radio - Using the RFu328 with ATmega328 microprocessor as a common platform emonTH can work with either an RFM12B or Ciseco SRF RF radio
Microcontroller: ATmega328 on RFu328 board Sensors: DHT22 (temperature & Humidity) / DS18B20 (temperature) sensor options Power: 2 x AA from on-board holder, LTC3525 3.3V DC-DC boost converter to extend battery life RF Radio: Using the RFu328 with ATmega328 as a common platform emonTH can work with either RFM12B or Ciseco SRF radio Battery life: 1-3 years expected, see blog post
DHT 22 Temperature & Humidity Sensor
Power supply 3.3-6V DC Output signal digital signal via single-bus Sensing element Polymer capacitor Operating range humidity 0-100%RH; temperature -40~80Celsius Accuracy humidity +-2%RH(Max +-5%RH); temperature <+-0.5Celsius Resolution or sensitivity humidity 0.1%RH; temperature 0.1Celsius Repeatability humidity +-1%RH; temperature +-0.2Celsius Humidity hysteresis +-0.3%RH Long-term Stability +-0.5%RH/year Sensing period Average: 2s Independent sensor test report
See getting started with the emonth: Getting started with the EmonTH
power consumption, absolute max values
Open-Hardware Design Files
EmonTH V1.4 Schematic diagram PNG emonTH_V1.4_Sch.png
EmonTH V1.4 Schematic diagram Eagle emonTH_V1.4.sch
EmonTH V1.4 Board files Eagle emonTH_V1.4.brd