emonTx TH V1.5
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 RFM69Pi) which then posts the data onto an emoncms server (e.g. http://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 Humidity sensing options - Using DHT22 temperature and humidity sensor, or if humidity is not required just a DS18B20 temperature sensor. Both DHT22 and DS18B20 can be used together as shown above for internal and external readings.
- 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.
- Update: the emonTH now supports multiple DS18B20's, see blog post
- New V1.5: Node ID select DIP switch: Set up to four unique node ID's via on-board DIP switch
- Microcontroller: ATmega328 @ 3.3V
- 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: RFM69CW (RFM12B can also be used)
- Battery life: 1-3 years expected, see blog post
- On-board LTC3525-3.3 DC-DC boost converter see emonTH hardware blog post
|Arduino||ATmega328 Port||Special Function||emonTH V1.5|
|Analog 0 (D14)||PC0|
|Analog 1 (D15)||PC1||2x AA Battery Voltage|
|Analog 2 (D16)||PC2|
|Analog 3 (D17)||PC3|
|Analog 4 (D18)||PC4||(SDA)||DHT22 Data|
|Analog 5 (D19)||PC5||(SCL)||DS18B20 One-wire Data|
|Analog 6 (D20)|
|Analog 7 (D21)|
|Digital 0||PD0||(RXD)||FTDI Tx|
|Digital 1||PD1||(TXD)||FTDI Rx|
|Digital 2||PD2||(int0) PWM||RFM12B IRQ|
|Digital 3||PD3||(int1) PWM||Terminal block|
|Digital 5||PD5||PWM||DS18B20 PWR|
|Digital 6||PD6||PWM||DHT22 PWR|
|Digital 7||PD7||DIP 1|
|Digital 8||PB0||DIP 2|
|Digital 10||PB2||(SS) PWM||RFM12B SEL|
|Digital 11||PB3||(MOSI) PWM||RFM12 SDI|
|Digital 12||PB4||(MISO)||RFM12 SDO|
|Digital 13||PB5||(SCK)||RFM12 SCK|
See getting started with the emonth: Getting started with the emonTH
DHT22 Temperature and 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
DS18B20 Temperature Sensor
- Power supply range: 3.0V to 5.5V
- Accuracy over the range of -10°C to +85°C: ±0.5°C.
- Storage temperature range:-55°C to +125°C (-67°F to +257°F)
RFM69CW RF module (default 433Mhz) is used to transmit data to emonBase (Raspberry Pi + RFM12Pi) or emonPi. The JeeLabs JeeLib Arduino library is used as the driver for the RFM69CW module. In JeeLabs packet format.
See blog posts:
The emonTH by default is shipped without the SMT USB mini-B connector since the standard case does not allow for use of the USB port to power the emonTH. However there has been a community contributed 3D printable case design contributed which does allow for use of the USB connector. The 3D CAD design for this case is up on Thingiverse:
Arduino compatible, a UART to USB cable is required to upload code
Open-Hardware Design Files
All the Design files for the emonTH are hosted on GitHub, see: 
Proudly open source
The hardware designs (schematics and CAD files) are licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
The firmware is released under the GNU GPL V3 license
The documentation is subject to GNU Free Documentation License
The hardware designs follow the terms of the OSHW (Open-source hardware) Statement of Principles 1.0.
Environmental & Life Cycle
We are passionate about sustainability and are aware of the embodied energy and use of resources involved in electronic manufacture. We try our best to reduce environmental impact wherever possible:
- We have recently been inspired by a few projects taking a lead in promoting and making steps towards Ethical and Sustainable Electronics, see our blog post we wrote on the topic .
- The PCB's are manufactured in the UK by a manufacturer who uses lead free techniques, complies to the highest environmental industry standard and is actively investing in techniques and equipment to reduce wastage and environmental impact (e.g water treatment and recycling). Hot-air leveling was chosen instead of immersion gold finish to reduce environmental impact.
- The assembly is also done in the UK with all components being RoHS compliant and free of conflict materials.
- Surface freight is used in preference to air shipping when ordering parts in bulk. This consumes 33 times less energy.
- We have strived to optimise electrical consumption in our hardware to be as low was possible and recommend the use of green rechargable batteries, see blog post
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