Depth cameras cost real money, which is why most student robots still steer by a single ultrasonic sensor. Samuel Alexander’s Depth Multitool shows another route: a plain USB webcam plus a neural network gives you a distance estimate for every pixel, at 20 frames per second, with no stereo rig, IR projector, or LiDAR.
The software runs Depth Anything V2 Small, a 25-million-parameter model, on the Qualcomm Dragonwing NPU inside the Arduino VENTUNO Q. It does monocular depth estimation, meaning it guesses relative distance from one ordinary image. Alexander built four modes on top of it. Heatmap blends the camera view with a bright-near, dark-far depth map. Slicer highlights only objects inside a depth range you move with the arrow keys. Flood fills the room with virtual water from the back forward. Sonar skips the screen and turns depth into clicks: low pitch for the left side, higher pitch for the right, faster as you approach a wall.
The tuning that made it fit
The tricky part was squeezing the model onto the board. He fed it a 336×252 input and kept full floating-point precision, because 8-bit quantization introduced artifacts and flattened the near field. Dropping resolution was the better trade. One inference takes about 16 ms, and capture, inference, and rendering run on three separate threads so the NPU starts the next frame while the screen draws the last one.
Power is the other gotcha. Pushing to roughly 30 FPS draws 15.2 W. Capping at 20 FPS in the NPU’s balanced mode drops that to 11.8 W, enough to run the board, a 10-inch display, and the webcam from a USB-C power bank. The onboard STM32 microcontroller stays untouched, so you could add vibration motors or buttons tied to the depth data later.
Build it yourself
- Borrow a USB webcam and a laptop first, and run a small depth model in Python to see the heatmap before spending on a VENTUNO Q.
- Try the Sonar idea on its own: split the depth map into left and right halves, average each, and map the number to a buzzer pitch on a GPIO pin.
- Measure board power with a USB meter at two frame rates, as Alexander did, and note where the watts jump.
Read the full write-up on Hackster.io, then check Arduino boards and USB webcams at circuit.rocks for a classroom-ready depth sensing experiment.
Frequently Asked Questions
How does a single webcam measure depth?
It uses monocular depth estimation. The Depth Anything V2 Small model predicts the relative distance of each pixel from one image, so no stereo pair, IR projector, or LiDAR is needed.
What hardware and power does the Depth Multitool need?
An Arduino VENTUNO Q, a USB webcam, and a 10-inch display. At 20 FPS in balanced NPU mode the setup draws 11.8 W, so a USB-C power bank can run it.
What will I learn if I build this?
You learn how to run a neural network on an NPU, trade input resolution against quantization artifacts, split capture, inference, and rendering across threads, and measure power draw. Those skills carry over to robot navigation and computer vision thesis projects.
