And so it’s time for the second instalment of our Internet of Things Collections blog series for eBay: the EMF Smog Box!
This episode is basically a deep-dive into one of my pet projects we released a little while ago: the Ondes Visible project.
The basic concept of this project is quite simple: making electro magnetic fields (aka EMFs) visible! EMFs surround us day and night. Some are generated by natural elements such as the Sun or the stars, others however are created by humans – mostly through the use of wireless technologies.
EMFs are invisible but scientists are not yet sure of the impact they have on our health, sleep patterns, moods, etc. especially when considering high-frequency fields (see for instance the results of the Interphone study, one of the biggest of its genre). So, visualising these fields is the first step towards awareness; plus it’s quite fun!
The project is composed of three main building blocks:
– An Arduino Uno or more recent controlling two EMF sensors: one for low-frequency fields (< 30 KHz) one for high-frequency fields (> 30 kHz)
– An Android phone to make sense of the sensor data and visualise it
– The Ondes Visible open-source app to learn more about what you are observing as well as to graph the data
‘Receipe’ time…
Again, all the ingredients you need can be found in the EVRYTHNG’s eBay Collections then simply follow the following steps and you should be good to go!
– Step One: building the sensors.
The EMF smog box project can sense two big families of EMFs: low-frequency and high-frequency fields. Examples of low-frequency fields are those generated by electric appliances, e.g. your alarm clock or a lamp.
Sensing them is easy and all you need is a wire and a resitor. Simply solder them together and you are good to go for sensing low-frequency fields (< 30 kHz).
Interestingly enough, low-frequency fields are also far less mysterious in terms of their impact on our health (tried putting your fingers in the power socket anyone? well don’t!).
Sensing high-frequency is much more interesting because those are harder to detect, generated by any modern wireless devices and their impact on our health still generates some controversies…
To build the high-frequency sensor we’ll need a LT5534 RF Power Detector and to solder it onto a protoype board. Unfortunately this component is only available as an SMD (Surface-Mount Device) which means it’s really small and challenging to solder. Make sure you order at least two of them just in case! A nice tutorial on this particular complex step is available here.
– Step Two: connecting the sensors to the Arduino
Next you’ll need an Arduino, the code we provide for the Arduino is expecting the low-frequency sensor to be plugged on the I/O pin 0 and the high-frequency sensor on pin 5 (see the lfAnalogIn and hfAnalogIn variables).
You’ll then need to upload the Arduino part of the project onto your board, use the Arduino IDE to upload it.
Once this is done, your Arduino will start receiving EMF data, we now need a way to visualise it: enter an Android phone!
– Step Three: connecting the Arduino to Android
For this part you’ll need an Android phone. We tested the software on a wide range of Android devices from 1.5 up to 4.2 but ideally no more than 4.2.
Then, you need to make sure your Arduino and Android are connected and understand eachother!
You basically have two ways of doing this: the official way, using an ADK (Accessory Development Kit) compatible Arduino board (e.g. Arduino Board ADK or, in the case of this project, using a “hack” of the ADB (Android Debug Bridge).
Working with the ADB requires an Arduino shield that supports to act as a USB Host so you’ll have to stack one of these on top of your Arduino.
– Step Four: installing the app on your Droid
The last part should be rather easy, just get the open-source Ondes-Visibles app from the Web of Things GitHub forge and you should be good to go!
The app not only helps you to visualise the fields but it will also give you more information about what EMFs are and what we know about their impact.
– Step Five: powering the whole thing
 If you want to get your prototype in the wild, you’ll need to add a 9 Volts battery to the kit. The only issue is that the greedy Droid will try to charge its own battery from that, which will drain the battery with an hour or so. To prevent this from happening you can solder a resistor to your USB cable, this will prevent your Android from charging but the data will still get through!
– Step Six: EVRYTHNG
To make it more fun (and more ‘Web of Things’!) you could also connect your shiny new device to the EVRYTHNG API to store and graph your measurements. Our Java SDK supports Android.
Wanting to go even further? The sensors pick the data, your Arduino sends it to your Droid over USB and the ADB, your Droid uses its GPS to upload both the data and then coordinates to the EVRYTHNG API and tadaaa: you can build maps of the electrosmog in your city, finding the EMF quiet zones! 😉
Watch this space for the next in the recipe blog series “Connected Coffee Machine” which will be live in the next couple of weeks, in the meantime, go and check out the rest of EVRTHNG’s eBay Collections.
