IoTBue Workshop – Getting closer to a real IoT device

Recently the Buenos Aires Internet of Things (IoTBue) Meetup held a workshop to train developers on IoT development from scratch.  This workshop was hosted by developers from R/GA, Patagonia Technology and Cran.io.

The goal was simple: build a Nest thermostat clone in 6 hours.  We split the exercise into 3 phases.  We established communications with the sensors, then added a simple temperature visualization, and then finally improved the sensor’s intelligence.

Phase 1 – Hello Arduino.

In this phase we explained how Arduino works and established a connection from a laptop to the Arduino using an Ultrasonic sensor.   We then used a DTH11 sensor to measure weather conditions like humidity, pressure, and temperature.

Phase 2- Live Dashboard.

Confident that the Arduino was working, we embarked on sending information to a server.  We used an Arduino Ethernet Shield to transmit data to a REST service that was hosted on Node.JS.

From there, we saved the information to a Mongodb instance using Mongoose and broadcast the updates to a frontend console using Socket.io. The front end also drew simple status graphics using d3.js.  We used the Google Starter Kit as main CSS bootstrap.  Quick and dirty but effective.

Phase 3- Add Intelligence.

Prediction based on data accumulation is the key to a smart IoT system.  In order to demonstrate this we  introduced everyone in the room to the theory of control systems by creating a control loop between the sensors, actioners, and measuring system.  The goal was to affect the system conditions actioning a “lamp” to increase temperature or a ventilator to reduce it.

For that we used a really simple but powerful formula to control when to use the activators


var dt = tint- tdest;
var dext = tempNext - tempNow;
var dint = dt + dext;

where:

• tint is the Current Internal Temperature from System.
• tdest is the Deseable Internal temperature setted by the user.
• tempNow is the Current Internal Temperature using Weather API.
• tempNext is the Upcoming Outside Temperature using Weather API.

One way of using this will be something like this:

var status = '';
if(dint>1.0){
status='COLD';
}
else if(dint<-1.0){
status='WARM';
}
else{
status='OFF';
}

This algorithm allows us to change the temperature of the environment smoothly.  If the system needs to warm (dint <-1), we turn on a light.  If system needs to get cool down (dint >1), we try the ventilator.  Otherwise, we do nothing.

Of course, this example doesn’t account for humidity or pressure, but these simplifications helped a convey the core concepts.  From here one could add additional constraints and control loops to improve upon the core.

The source code for NestRemix is available here: https://github.com/IotBue/nestRemix

A live example of the platform is online at http://nest-remix.herokuapp.com/dashboard/arduino20

With this 3 phases we made created a solid foundation for future IoT projects using off the shelf components and a few clever tricks.