The Automatic Barrier Controller is a compact, single-PCB automated gate entry system designed for mini-projects, parking models, or toll boom barriers.

System Architecture & Flow

Microcontroller (ATtiny85): The 8-pin DIP IC serves as the core processor, reading sensor signals and executing simple conditional logic to actuate the servo motor.

Ultrasonic Distance Sensor (HC-SR04/HY-SRF05): Plugs directly into the header labeled "Ultra Sonic". It emits an ultrasonic burst to detect approaching objects (vehicles) within a programmed distance threshold.

Servo Motor Actuator (SG90 or similar): Connected via the 3-pin "SERVO" header ($5\text{V}$, GND, PWM Signal). It acts as the physical barrier/tailgate arm, rotating 90(Degree) to open when triggered.

Visual Status LEDs: "Red" signals a closed barrier (Stop), while "Green" lights up when the object is detected and the gate lifts (Proceed).

Low Voltage Operation (5V): Powered directly through the 2-pin "INPUT" terminal using a standard 5V power source (USB, power bank, or standard adapter).

Operation Sequence

Idle State: The ATtiny85 holds the servo at 0 (Degree) (barrier down) and lights up the Red LED.

Detection: The ultrasonic sensor continuously calculates distance. When a vehicle comes within range, it sends a trigger signal to the MCU.

Trigger: The ATtiny85 turns off the Red LED, turns on the Green LED, and sends a PWM signal to rotate the servo to 90 (Degree) (barrier opens).

Auto-Reset: After a pre-set delay (allowing the vehicle to pass) or once the sensor reads the path clear, the MCU swings the servo back to 0 (Degree) and switches back to the Red LED.