TongDou Desktop Robot Sees You Coming With 24GHz Radar

A Desk Gremlin With Better Sensors Than Your Doorbell

TongDou is an open-source desktop companion robot from an independent developer, and the parts list is more interesting than the category usually allows. An ESP32-S3 for the brain, a brass chassis, an OLED display for a face, a pair of gearmotors driving wheels, a speaker for pre-recorded voice lines, and — the choice worth talking about — a 24 GHz radar module alongside an IMU for spatial awareness.

• ESP32-S3 microcontroller driving the whole system, with an OLED display serving as the robot's face
• 24 GHz radar plus an IMU for presence detection and orientation, rather than the usual PIR or ultrasonic sensing
• Brass chassis with two gearmotors for wheeled locomotion, plus a speaker for pre-recorded audio responses
• Design files published on GitHub so others can build their own; the project is also documented on Hackaday.io

Why Radar Instead of a Cheap PIR Sensor

Passive infrared is the default presence sensor for hobby projects because it costs almost nothing, and it has two failure modes that matter enormously for a desktop companion. It only detects *motion*, so a person sitting still reads as an empty room. And it triggers on any warm moving mass, including a radiator cycling or sunlight moving across a wall.

A 24 GHz radar module detects presence rather than movement — it will register a person sitting perfectly still at a desk, which is the actual state of the person this robot is meant to keep company. It also sees through plastic enclosures, works in complete darkness, and is unbothered by thermal noise. For a device whose entire premise is reacting appropriately to whether someone is there, that is the difference between charming and broken.

Is an ESP32-S3 Enough for a Robot?

For this one, comfortably. The workload is motor control, an OLED refresh, audio playback, radar and IMU polling, and some state logic — well within the dual-core S3's budget, with the vector instructions and PSRAM headroom left over for anyone who wants to add wake-word detection later.

The S3 also brings Wi-Fi and Bluetooth as a given, which turns a standalone desk toy into something that can react to network events: a build finishing, a calendar reminder, a sensor elsewhere in the house. Our low-power wireless MCU guide walks through why the S3 has become the default pick for this class of always-on, mostly-idle device, and TongDou is a textbook case of the fit.

What Makes the Brass Chassis a Good Call?

Mostly that it is not 3D-printed plastic, which is the aesthetic default for open-source robotics and the reason so many of these projects look like prototypes forever. Brass machines cleanly, takes a finish, has enough mass to keep a small wheeled robot from skittering, and ages into something that looks deliberate rather than unfinished.

There is a practical benefit too: a metal chassis is a decent thermal path and a reasonable ground plane, both of which are small mercies in a compact build with motors and a radio in close quarters. It is the sort of choice that suggests the developer cared about the object as an object, not only as a demo.

Building Your Own

Design files are on GitHub under the project name, with a build log on Hackaday.io. The bill of materials is modest — an ESP32-S3 board, a 24 GHz radar module, an IMU, a small OLED, two gearmotors, a speaker, and the chassis — putting this well within reach of anyone who has finished a maker project at the level of the Open RC Spotter telemetry logger we covered recently.

The genre of desktop companion robots is crowded with things that wave and do nothing else. Choosing a sensor that actually solves the presence problem is what separates this one from a novelty, and it is a design lesson worth stealing regardless of what you are building.

Sources: Hackaday — July 31, 2026; TongDou on GitHub — July 2026; Hackaday.io project page — July 2026.