The Simplest Ultrasound Sensor Module, Minus The Module

Just about every “getting started with microcontrollers” kit, Arduino or otherwise, includes an ultrasonic distance sensor module. Given the power of microcontrollers these days, it was only a matter of time before someone asked: “Could I do better without the module?” Well, [Martin Pittermann] asked, and his answer, at least with the Pi Pico, is a resounding “Yes”. A micro and a couple of transducers can offer a better view of the world.

The project isn’t really about removing the extra circuitry on the SR-HC0, since there really isn’t that much to start. [Martin] wanted to know just how far he could push ultrasound scanning technology using RADAR signal processing techniques. Instead of bat-like chirps, [Martin] is using something called Frequency-Modulated Continuous Wave, which comes from RADAR and is exactly what it sounds like. The transmitter emits a continuous carrier wave with a varying frequency modulation, and the received wave is compared to see when it must have been sent. That gives you the time of flight, and the usual math gives you a distance.

Since he’s inspired by RADAR, it’s no surprise perhaps that [Martin]’s project reminds us of SDR, and the write-up gets right into the signal-processing code. Does it work better than a chirping module? Well, aside from using fewer parts, [Martin] can generate a full range plot for all objects in the arc of the sensor’s emissions out to 4 meters using just the Pico. [Martin] points out that it wouldn’t take much amplification to get a greater range. He’s not finished yet, though — the real goal here is to measure wind speed, which means he’s going to have to go full Doppler. We look forward to it.

This isn’t the first time we’ve seen the Pico doing fun stuff at these frequencies, and Doppler RADAR is a thing hackers do, so why not ultrasound?