Development History of Smart Toilets
As an upgraded version of traditional toilets, smart toilets integrate advanced intelligent technologies and achieve precise control through microcomputers. Originating in the United States, they were initially mainly used in medical and elderly care fields, only featuring basic warm-water washing functions. Over time, this innovative product was gradually developed and improved in South Korea and Japan. Manufacturers continuously added new functions such as heated toilet seats, warm-air drying, and sterilization, significantly enhancing the user experience. Today, smart toilets have become a popular bathroom fixture in modern homes. With a wide variety of products on the market, they offer increasingly diverse functions, including hip cleaning, lower-body cleaning, mobile cleaning, seat heating, automatic deodorization, etc., providing users with a more comfortable, convenient, and hygienic experience.
Principles of Radar Sensing Technology
Radar is an advanced electronic device that detects targets using electromagnetic waves. Its working principle is based on the transmission and reception of electromagnetic waves: radar emits electromagnetic waves into the target area, and when these waves encounter target objects, they reflect back. By accurately analyzing the echo signals, radar can obtain key information about the target relative to the emission point, including distance, range rate (radial velocity), azimuth, and angle.
In smart toilets, radar sensing technology typically uses 24GHz radar sensors. These sensors employ planar microstrip antenna technology, offering significant advantages such as compact size, high integration, and high sensitivity. They primarily operate in two modes: CW Doppler radar sensor mode and FMCW radar sensor mode.
- CW Doppler Radar Sensor Mode: The sensor transmits at 24GHz. By calculating the frequency difference between the transmitted and received signals and using specific formulas, it accurately measures the object’s movement speed. After mixing the reference signal with the echo signal, the dual-channel sensor outputs two intermediate-frequency signals (IF1 and IF2) with the same frequency amplitude but a 90° phase difference. The system determines the object’s movement direction (away or approaching) based on the signal type guided by this 90° phase difference.
- FMCW Radar Sensor Mode: Suitable for measuring object distance, such as detecting the distance from stationary objects to the sensor. This mode uses linear up-chirp or down-chirp as the time-varying function for the transmission frequency, repeating these chirps periodically to obtain reliable average values. Object distance is calculated using the delay effect formula.
Functional Implementation of Radar Sensing in Smart Toilets
Automatic Lid Opening/Closing
One key application of radar sensing technology in smart toilets is the automatic lid opening/closing function. When a user approaches the toilet, a radar sensor installed on the lid quickly detects the human presence. For example, Holatek’s hlk-ld2411 radar module, specially developed for smart toilet scenarios, supports detecting human approach/retreat within 2 meters. When a user enters the 2-meter range, the hlk-ld2411 module敏锐ly (keenly) detects the movement and outputs a GPIO signal to the microcontroller, which then controls the motor to rotate forward at an appropriate speed to open the lid automatically, eliminating the need for manual operation. After use, when the user leaves, the radar sensor detects the retreat, and the microcontroller controls the motor to reverse, closing the lid and putting the system into standby mode. This prevents inconvenience and hygiene issues caused by forgotten lid closure.
Automatic Flushing
Radar sensing technology also plays a critical role in the automatic flushing function. During use, the radar sensor continuously monitors the user’s presence. Once it detects that the user has moved away and meets preset time and distance conditions, the toilet automatically initiates flushing. For instance, in some designs, as the user moves away from the Doppler sensor, the microwave detection device continuously measures distance. When the maximum effective distance is detected, the toilet executes the flushing action based on pre-set commands. This not only automates flushing but also precisely controls the timing to avoid water waste, while eliminating the need for manual flushing, enhancing convenience and hygiene. Additionally, some smart toilets use radar sensing to distinguish user habits—for example, triggering a small-volume flush after a male user stands to urinate and leaves, while applying different flushing modes for female users or other scenarios, enabling personalized and intelligent flushing.
Anti-Misoperation Function
Millimeter-wave radar technology is widely used in smart toilet anti-misoperation systems, enhancing accuracy and stability. The Quanyao TTCSensor millimeter-wave radar TRMK345 emits and receives 24GHz millimeter waves to sense target distance, real-time outputting data on distance, angle, speed, and energy. Its key advantage lies in mobile target trajectory positioning and zone-sensitive partitioning via radar azimuth self-identification technology, with flexible on/off configuration for excellent anti-misoperation effects.
In practical use, the radar monitors real-time human activities in the bathroom, including position, movements, and posture. When detecting someone approaching, the system activates anti-misoperation mode, using intelligent algorithms to analyze behavior. For example, it can distinguish between humans and pets by analyzing target characteristics, preventing misoperations like accidental lid opening or flushing.
Non-contact detection via millimeter-wave radar avoids hygiene issues from physical contact and improves system reliability. With high precision and low power consumption, it accurately measures distance and speed to determine user proximity and movement, ensuring reliable behavior recognition in complex environments. Its low power consumption also extends the system’s lifespan and reduces energy use.
Other Functional Extensions
Beyond the main functions, radar sensing technology enables additional features in smart toilets:
- Automatic Indicator Lighting: Some models use radar modules to auto-activate/deactivate indicator lights. When a user approaches, the radar detects the signal and turns on the light for illumination in low-light conditions; it turns off after the user leaves, saving energy.
- Gesture Control for Seat Rings: High-end models employ radar-based gesture sensing, allowing users to flip the seat ring up/down with simple gestures (e.g., waving), enabling contactless operation and enhancing convenience and hygiene. This is particularly helpful for users with mobility issues or those holding items, making smart toilets more user-friendly.
