LED auto-off timer using built-in LED
Hardware Required
- PICUNO Microcontroller board (built-in LED on GPIO 14)
- USB cable (for power and programming)
Description
When the program starts, the LED connected to GPIO 14 turns ON. After a delay of 5 seconds, the LED is turned OFF automatically. This demonstrates a basic event-timer mechanism where GPIO output is controlled based on elapsed time.
Circuit Diagram
Circuit
- Connect the PICUNO board to the computer using a USB cable.
- No external wires or breadboard are required.
- The built-in LED is internally connected to GPIO 14.
- The program automatically handles turning the LED ON and OFF.
Schematic
This project uses the built-in LED on GPIO 14 of the PicUNO board. No additional circuit components are required.
Code - C
int ledPin = 14; // Built-in LED pin
unsigned long startTime;
void setup() {
pinMode(ledPin, OUTPUT);
digitalWrite(ledPin, HIGH); // Turn LED ON
Serial.begin(9600);
Serial.println("LED is ON");
startTime = millis();
}
void loop() {
if (millis() - startTime > 5000) {
digitalWrite(ledPin, LOW); // Turn LED OFF
Serial.println("LED is OFF");
while (true); // Stop loop after turning OFF
}
}
unsigned long startTime;
void setup() {
pinMode(ledPin, OUTPUT);
digitalWrite(ledPin, HIGH); // Turn LED ON
Serial.begin(9600);
Serial.println("LED is ON");
startTime = millis();
}
void loop() {
if (millis() - startTime > 5000) {
digitalWrite(ledPin, LOW); // Turn LED OFF
Serial.println("LED is OFF");
while (true); // Stop loop after turning OFF
}
}
pinMode() - Sets GPIO 14 as output.
digitalWrite(ledPin, HIGH) - Turns ON the LED.
millis() - Tracks elapsed time since startup.
Once 5 seconds pass, the LED is turned OFF and the loop is halted.
digitalWrite(ledPin, HIGH) - Turns ON the LED.
millis() - Tracks elapsed time since startup.
Once 5 seconds pass, the LED is turned OFF and the loop is halted.
Code - Micropython
from machine import Pin
import time
led = Pin(14, Pin.OUT)
led.value(1) # Turn LED ON
print("LED is ON")
start_time = time.ticks_ms()
while True:
if time.ticks_diff(time.ticks_ms(), start_time) > 5000:
led.value(0) # Turn LED OFF
print("LED is OFF")
break
import time
led = Pin(14, Pin.OUT)
led.value(1) # Turn LED ON
print("LED is ON")
start_time = time.ticks_ms()
while True:
if time.ticks_diff(time.ticks_ms(), start_time) > 5000:
led.value(0) # Turn LED OFF
print("LED is OFF")
break
Pin(14, Pin.OUT) - Initializes GPIO 14 as output.
led.value(1) - Turns LED ON at program start.
time.ticks_ms() - Captures start time in milliseconds.
time.ticks_diff() - Calculates time difference for non-blocking delay.
After 5 seconds, the LED is turned OFF and program exits.
led.value(1) - Turns LED ON at program start.
time.ticks_ms() - Captures start time in milliseconds.
time.ticks_diff() - Calculates time difference for non-blocking delay.
After 5 seconds, the LED is turned OFF and program exits.