Air Quality Cloud

This project is about monitoring air quality indoors and visualizing it in a fun and tangible way. The Air Quality Cloud measures a wide range of air pollution parameters and turns into a toxic purple colour (or really any colour you'd like). The cloud is meant to be hung in the corner of a crowded room, e.g. a classroom and signalizes the need to ventilate.

This project is part of the course "Free and Open Technologies" at TU Wien. It was created during workshops and with inspiration of other similar approaches like this.

We used the following materials:

• Arduino Uno
• MQ135 air quality sensor
• Active buzzers
• "Neopixel" LED string lights
• Power bank
• Styrofoam
• Cotton wool

Of course, the project can be adjusted in many ways and different materials at hand can be used. The cotton wool is a very classic approach to a cloud-like look, but it really depends on what the outcome should look like. The sensors, buzzers and LED light can also be exchanged for similiar parts, you would of course need to adjust the code in this case.

The basic electronics can be found in the above curcuit diagram. The MQ135 has two outputs, which are both connected to the Arduino, but only the analogue one is used in our case. The buzzers are connected in parallel to make a louder sound.

We soldered the components to wires and the other end to dupont connectors for easy attachment to the Arduino board. We suggest leaving the wires to the sensor longer to be able to attach it outside the "cloud" at an appropriate height. You want to measure the air quality at the level of people's heads and the cloud might be mounted higher.

We found a styrofoam mannequin head which we cut the head off and hollowed it out for a housing, but you can use whatever you have lying around. It just has to be big enough for the electronics plus the power bank, and the LEDs and cloud materials have to fixed to the outside.

We glued the LED stripes to the outside with hot glue (Attention, the styrofoam melts easily!) and soldered wires to connect the individual segments. One end was soldered to wires with dupont connectors and connected to the Arduino.

When everything is connected, the Arduino code can be flashed and tried out. You should be able to read the analogue sensor values (0-1000) in the Arduino serial console. The sensor can be tested be holding a lighter under it and pressing the button to release gas (don't light it). A small container with alcoholic liquid beneath the sensor also works pretty well.

When the sensor value goes above 400, the buzzers start beeping. The colour of the LED lights changes from white to purple. All of this can be changed, different colours could be used and you could even program thunder sounds and lightning effects.

The configuration of the specific LED strip is in the lines 7-10, you might need to change that to your type of LEDs and also the used length of strip. The digital value of the sensor is unused, but can of course be integrated, e.g. as trigger for the sound. The MQ135 board has a small potentiometer to change the threshold of this value.

The electronics were strapped to the powerbank as a basis with cable ties and put inside our hollow styrofoam housing. The outside with the LEDs attached was covered with cotton wool (glued to the styrofoam) that was additionally fixed with hair spray. Feel free to try different materials and styles.

We attached a string to the cable ties and hung it upside down, so the LED could be seen from below. The air quality sensor is outside the cloud to be able to mount it independently.