Project
| # | Title | Team Members | TA | Documents | Sponsor |
|---|---|---|---|---|---|
| 95 | Chair-Mounted Anti-Sedentary Detection System with Enforced Movement Clearing |
Chris Huang Jack Gaw Melissa Wang |
Gayatri Chandran | design_document1.pdf proposal1.pdf |
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| # Team Members: - Chris Huang (zexih2) - Melissa Wang (wang569) - Jack Gaw (jgaw3) # Problem Students and office workers often spend long periods sitting at their desks, which can negatively affect physical health, focus, and productivity. Many existing reminder systems, such as phone notifications or simple alarms, are easy to ignore or turn off without actually getting up. As a result, these systems do not effectively reduce prolonged sitting. There is a need for a system that not only detects extended sitting, but also encourages users to physically get up and move in a simple and practical way. # Solution We propose a chair-mounted system that monitors how long a user has been sitting and triggers an alarm after a configurable time threshold. A pressure-based sensor detects whether the user is seated and tracks continuous sitting time. When the sitting time exceeds the threshold, an alarm is activated and cannot be dismissed while the user is still seated. After the user stands up, the system switches to a movement detection mode. All sensors are mounted directly on the chair, and no wearable devices are required. Movement near the chair is detected using vibration and inertial sensors mounted on the chair frame or legs. The alarm is cleared only after the system detects enough movement consistent with short-distance walking. The system is implemented using a simple state-machine-based embedded design and is divided into multiple subsystems, including seat detection, movement detection, user feedback, and a main controller. # Solution Components ## Subsystem 1: Seat Occupancy Detection This subsystem determines whether a user is sitting on the chair and measures how long the user remains seated. The signal is filtered to reduce noise and prevent false transitions. Components: - Force-sensitive resistor (FSR-402) mounted under the seat cushion, or - Load cell sensors mounted under the chair supports - HX711 load cell amplifier (for load cell configuration) - Basic signal conditioning resistors ## Subsystem 2: Chair-Mounted Movement Detection This subsystem checks whether the user has stood up and moved around near the chair. Sensors are mounted on the chair structure to detect vibrations and motion caused by footsteps. This approach is chosen for simplicity and ease of use, even though it is less precise than wearable step counters. Components: - Piezo vibration sensors mounted on chair legs or base - Optional MPU-6050 IMU mounted on the chair frame - Analog and I2C connections to the controller ## Subsystem 3: Alarm and User Interface This subsystem provides feedback to the user and allows basic interaction with the system. Components: - Active piezo buzzer - LEDs for status indication - Push buttons for configuration and reset - Optional small OLED display ## Subsystem 4: Main Controller and Power The main controller coordinates all subsystems, runs the state machine, and controls alarm behavior. All electronics are mounted on the chair and powered locally. Components: - ESP32 microcontroller - USB 5V power supply or rechargeable battery - Wiring and mounting hardware # Criterion For Success 1. The system correctly detects whether the user is seated or not during repeated sit and stand actions. 2. The alarm activates within a few seconds of the configured sitting-time threshold. 3. The alarm cannot be permanently turned off while the user remains seated. 4. After standing up, the alarm is cleared only after sufficient movement near the chair is detected. 5. Simple actions such as tapping or shaking the chair while seated do not clear the alarm. 6. The system can successfully complete multiple full cycles of sitting, alarm triggering, movement detection, and reset without failure. |
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