Damp Pi - Room Moisture Extraction System

Annoyed with the excess of humidity in the shower room, a blogger named David Hunt decided to fix the problem in his own unique way. Instead of installing extractor fans with built-in timers or temperature sensors, he built a setup termed as Damp Pi, where a minicomputer could read the humidity values from the sensor and on the basis of the readings, the fan could be turned on until the humidity came down to the normal level. Although David used Raspberry Pi in this project, one can choose among various other options like Intel Edison, Intel Galileo, Beaglebone Black, Beaglebone Green, Creator CI20, and so on.

Figure 1: Damp Pi

In order to prepare this humidity system, the list of required materials consist of an extractor fan, AM2302 temperature and humidity sensors, a dual A/C relay board, signal wiring breakout board and Raspberry Pi. Although everything could be connected directly to the Pi, David thought that it would be simpler to break down the wiring with the help of a breakout board.

Getting started with the fan, it’s a 230V unit that is fitted to the wall by making a 120mm hole through the leaves of 100mm concrete block. It also contains a vent that opens when the air is pushed out of the system. In order to supply power, the fan wires are fed into the main cables that are covered in plastic conduits and these are fed back to the relay board. It takes an extra effort to smooth up the wall with fillers and then need to be painted so as to conceal all the wiring.

Similarly, the humidity sensors are tapped near the ceiling with a screw at a place such that it is easy to feed the wires up to the roof from where they can be connected to the breakout board.

As far as the major electronic components are concerned, these are kept aloof in a box and fitted on an acrylic sheet with the help of stand-offs so that the whole setup can be placed conveniently on the roof. Moving on, the configuration part of the circuit is quite straight forward. The breakout board supplies 5V and GND to each of the pin headers of the sensors and relay board respectively. Apart from this, there is a data signal from sensor and 2 activation signals from the Relay board.

For the software, David used a combination of ThingSpeak and Adafruit to read the sensor, along with Wiring Pi and Wiring-Python for driving the relay GPIOs. After the completion of the assembly, the temperature and humidity readings are studied every minute and these are fed to the Raspberry Pi. In this project, when the readings were above 90% the extractor fan was switched on through the relays. When the readings dropped below 80%, the fan would be switched off.

If you wish to make your own humidity extractor, you can check out the link below, which contains a detailed explanation of the procedure.