“Just a small project to demonstrate the Doppler effect using ultrasonic sound and the absolute minimum of components.
Let me skip the theory, you can it read elsewhere. Just upload the code and enjoy.
Well, of course you need an ultrasonic transmitter (left side of the picture, the NANO connected to the turquoise cable) and the receiver (the NANO connected to the red cable). You can get the modules separately or dismantle one of that cheap HC-SR04 modules which are meant for distance measuring by echo. Ultrasonic modules have a very sharp beam, so both of them have to look at each other. To achieve this, just cut a card board and give it a shape like rails.”