OVERVIEW

This project is a PCB-based digital hourglass that uses an ESP32-S3 microcontroller, an OLED display, an orientation sensor, and an ambient light sensor. The device displays an hourglass animation, detects when the board is flipped, and automatically adjusts screen brightness based on surrounding light.

SYSTEM BLOCK DIAGRAM

System starts with USB-C power, regulates it to 3.3V, then the ESP32 reads the sensors and drives the OLED display.

DESCRIPTION

The Auto-Dim Digital Hourglass is designed as a compact embedded system that combines sensing, display control, and power regulation on a custom PCB. A BMI270 IMU detects board orientation and flipping behavior, while a VEML7700 ambient light sensor measures room brightness. The ESP32-S3 processes these inputs and controls a 2.42-inch 128×64 OLED display to show the hourglass animation. The board is powered through USB-C, protected using fuse/TVS/ESD components, and regulated from USB 5V down to 3.3V for the ESP32 and sensors.

FEATURES

• ESP32-S3-WROOM-1 main microcontroller

• 2.42-inch 128×64 SSD1309 OLED display

• Hourglass animation displayed on OLED

• BMI270 IMU for flip/orientation detection

• VEML7700 ambient light sensor for auto-dimming

• USB-C power input

• 5V to 3.3V buck regulation using AP63203

• PTC resettable fuse for overcurrent protection

• TVS diode for USB power-line surge protection

• Reset and boot buttons for programming/debugging

• Test points for power rails and debugging

• Front and back GND copper pours for improved grounding

CIRCUIT CATEGORIES

• Compute: ESP32-S3 controls the system and runs the hourglass logic

• Power: USB-C input, fuse protection, TVS protection, and 5V-to-3.3V buck regulator

• Sensing: BMI270 orientation sensor and VEML7700 ambient light sensor

• Actuation / Output: OLED display shows the digital hourglass animation

CIRCUIT DESIGN

The board receives 5V from the USB-C connector. The 5V line passes through a PTC resettable fuse and protection circuitry before feeding the buck regulator. The AP63203 buck regulator converts 5V to 3.3V, which powers the ESP32-S3, sensors, and OLED display.

The VEML7700 and BMI270 communicate with the ESP32 through a shared two-wire sensor bus. The OLED display uses a 7-pin SPI-style interface with clock, data, reset, data/command, and chip-select lines. The ESP32 uses the BMI270 readings to detect when the board has been flipped and uses the VEML7700 readings to adjust OLED brightness.

SCHEMATIC

PCB LAYOUT

BILL OF MATERIAL

ASSEMBLED PCB

EXPECTED OUTCOME

Team Members

HOPE Advisors