Circuit based on STM32 (Adafruit HUZZAH32 – ESP32 Feather Board) and a digital output (I2S) MEMS microphone (INMP441 or SPH0645LM4H) that detects beeping washing machine or dryer and sends notification to smartphone.
- Requires arduinoFFT, A library for implementing floating point Fast Fourier Transform calculations on Arduino (can be integrated using the Arduino IDE Library Manager ) https://www.arduino.cc/reference/en/libraries/arduinofft/
- If you like to use Pushover app on a smartphone for notification, you can manually integrate this library: https://github.com/ArduinoHannover/Pushover
- Other ways of notifications are also possible (e.g. Node-RED )
- ESP32 board with I2S onboard (e.g. Adafruit HUZZAH32 – ESP32 Feather Board)
- Digital microphone (e.g. INMP441 or SPH0645LM4H)
If your washing machine or dryer is located in the basement, you often are unsure if it already has finished its work. Continuous nagging questions of your partner like "Did the washing machine already beep" can drive you crazy. With this solution, you can install a small circuit in the basement next to the washing machine, and let it send you (and your partner) a push notification on the smartphone as soon as the washing machine has finished.
I2S_WS <--> D25
I2S_SD <--> D22
I2S_SCK <--> D26
Note: I had some problem with selecting the left channel for the INMP441- Either the
data sheets are wrong, or the manufacturer does not stick to it for some versions of it.
The Word Select (WS) signal equals the sample rate of 44.100 kHz.
The Serial Clock (SCK) is 2 x 16 x 44100 Hz = 1.54 MHz
STM32 microcontrollers already has Wi-Fi on board, so it is easy to connect to the local WLAN as soon as the beeping of the washing machine is detected.
The microphone uses a sample rate of 44100Hz and sends the audio samples to the STM32 using the I2S protocol
The STM32 uses a library to do a Fast Fourier Transformation and returns the most dominant frequency (peek frequency).
If this peak frequency is stable more than 500ms, then is can be interpreted as a beep of the washing machine, and the notification can be triggered.
- Could add code to distinguish the beep codes (frequency, rhythm of beeep) of several machines, enabling to distinguish between washing machine and dryer.
- Optimization of sample rate and number of samples for FFT analysis.
- DroneBot Workshop https://dronebotworkshop.com/esp32-i2s/
- Arduino Hannover User Group: https://github.com/ArduinoHannover/Pushover