node-red-contrib-htu21d ======================== A Node-RED node to query and receive data from [Measurement Specialities HTU21D](http://www.meas-spec.com/product/humidity/HTU21D.aspx) humidity and temperature sensors. These pre-calibrated sensors are interfaced using the I2C bus. The node also calculates the dewpoint temperature from the measured humidity and temperature. Install ------- Use npm to install this package locally in the Node-RED data directory (by default, `$HOME/.node-red`): cd $HOME/.node-red npm install node-red-contrib-htu21d Alternatively, it can be installed globally: npm install -g node-red-contrib-htu21d The nodes will be added to the palette the next time node-RED is started. Requirements ------------ This node uses the [htu21d](https://www.npmjs.com/package/htu21d) npm package to access the device over an I2C bus. This is generally supported only on Linux. The bus device name (e.g. /dev/i2c-1) is configurable: only one actual sensor is allowed on each bus, but the bus can be shared with any other I2C device not using the (7-bit) address 0x40. Usage ----- The output message payload holds the following properties: **humidity** - relative humidity in % **temperature** - temperature in ˚C or ˚F as configured **dewpoint** - calculated dewpoint in ˚C or ˚F as configured Measurements are repeated at a configurable interval: each measurement takes just over 0.1 second.