WOMB is an interactive installation that invites the participant to exit the current environment momentarily by stepping inside a space of comfort and distant familiarity.
The project is headed by Brustudio, a design and architecture trio who develop projects “with the intent of combining social and economic solutions with playful design to overcome challenges of everyday life”.
My role in the WOMB project is to design an automated sensor and audio system for the installation as well as composing the music itself.
The Raspberry was in charge of registering distance data of the installation door and playing audio. If the door was open, the audio would stop / not be playing. If the door was closed (ie someone had entered the exhibition) the audio would play.
As the ECHO output from the sensor outputs a 5v signal, a level shifter was needed to prepare a 3.3v signal for the GPIO pins of the Raspberry Pi.
Voltage transformer receives:
Built using Raspian Bullseye. All libraries are preinstalled with the OS. The script was set to run automatically on boot:
sudo nano /etc/rc.local
exit 0. The ampersand is used if a program runs in an infinite loop.
sudo python3 /home/pi/WOMB-Installation/raspi-files/python/SR04-sensor1.03.py &
#!/usr/bin/python3 # https://www.youtube.com/watch?v=JvQKZXCYMUM import RPi.GPIO as GPIO import pygame from threading import Thread from signal import signal, SIGTERM, SIGHUP, pause from time import sleep from gpiozero import DistanceSensor pygame.mixer.init(frequency=44100, size=-16, channels=2, buffer=512) audio_file = pygame.mixer.Sound('/home/pi/WOMB-Installation/raspi-files/audio/womb-track-2.01-16bit.wav') reading = True # give arguments for sensor. Max distance is the furthest distance to raed. # Threshold distance is the crossover value to use in conjunction with methods .when_in_range and .when_out_of_range sensor = DistanceSensor(echo=24, trigger=23, max_distance=1, threshold_distance=0.2) def safe_exit(signum, frame): exit(1) def play_audio(): audio_file.play() def stop_audio(): #audio_file.stop() pygame.mixer.fadeout(3000) def read_distance(): while reading: print("Distance (cm): ", sensor.distance * 100) sleep(0.1) sensor.when_in_range = play_audio sensor.when_out_of_range = stop_audio signal(SIGTERM, safe_exit) signal(SIGHUP, safe_exit) try: # Here using threading to keep processes controlled and code cleaner. reader = Thread(target=read_distance, daemon=True) reader.start() pause() except KeyboardInterrupt: pass finally: reading = False sensor.close()
The sound system comprises of:
Construction took place at WOODBOOM in Lichtenberg, Berlin. The structure is modular so it can be easily assembled / reassembled and transported.
The Raspberry Pi and sensor were installed in the side of the top most central panel, facing inner face of the sliding door.
Even though the trigger and echo membranes were receded approx 0.5-1cm inside the wood, there was no loss in measurement accuracy or performance.
The exhibition ran for two days, eight hours continuous each day. Over these two days, there was only one technical malfunction.
About four hours into the first day, the music started to sporadically restart, play for 10 or so seconds, then restart again. This happened in a loop.
I checked the readout of the distances, and even though with the door closed (which equals a distance from sensor to door frame of approx 4cm), the sensor was moving between 8-10cm.
threshold_distance in the sensor setup was set to 0.1m, the music was being restarted.
To account for this, I changed the
threshold_distance to 0.2m.
I’m still not sure what exactly caused this sudden change in behaviour. It could’ve been the heat (as the raspberry was at the top of an enclosed thick wooden box with no ventilation holes, and the exhibition was outside in direct sunlight on a 32 degree day 😅) or it could have been from the repetitive shock of the heavy sliding door hitting the panel where the sensor was installed. Perhaps a membrane of the sensor got vibrated out of position?
In any case, a threshold of 20cm is still a very safe range to register the sliding door being open / closed.
Overall, The exhibition went great and I wouldn’t have done much different except for two thoughts for next time: