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[IoT Home Project] Part 3 - Node.JS Module that reads sensor data

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In this post we will continue developing the IoT Home Project, by creating a module for Node.JS that reads the sensor data.

Why we create a Node.JS module?
We want to group all the logic that reads sensor data under the same roof. We design the module in a such a way that it will allow us to initialize an instance of an object that can read all sensors data.

GrovePiSensors Module
The module was is called GrovePISensors and expose 5 functions:
  • getSoundData - Gets Sounds data
  • getTempAndHumData - Gets Temp and Humidity data
  • getDistanceData - Get Distance data from Ultrasonic sensor
  • getLightData - Get Light data
  • getAllSensorsData -  Get all sensors data that can be read
The getAllSensorsData returns an object, where all this information are available. The sound information are not collected because it seems that personally I have some problems with the sensor. I'm not able with my board to collect data from sound sensor.

As you can see in the constructor, I have some predefined pins for each sensor. I have the following configuration:
  • DHT Sensor - pin 2  (digital)
  • Ultrasonic Sensor - pin 4 (digital)
  • Light Sensor - pin 2 (analog)
  • Sound Sensor - pin 0 (analog)
, but the constructor allow us to configure the pins as we want. Be careful, not to mix analog with digital pins and sensors. 
By default I log all the information that is read from the sensors in the console, but you can disable this from the constructor if you specify debug to false (default value is true).

From app.js I just initialize the board and read the sensors data. For now, I don't use this.

Lesson learns at this step
  1. I forgot to write an 's' to 'module.exports' and I spent around 2 hours trying to figure our why the module is not working.
  2. There are two types of sensors, digital and analog. If you don't connect them on the right pin, you'll get random data. 
  3. If you are careful you can connect/disconnect sensors while your app is running.
  4. Try to test each sensor after you write the first lines of code that read data from it.
  5. The light sesor show a high value when the light is low. A lower value means that the light level is high.
Next step
Connect to Azure IoT Hub and push this data to cloud.

Next post: [IoT Home Project] Part 4 - Sending temperature data from Raspberry PI to Azure IoT Hub


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