10-minute interval timer
Working prototypeAn Arduino timer that lights one of six LEDs every 10 minutes, prototyped on a breadboard.
- Based on the Digital Hourglass project from the Arduino Starter Kit, then modified.
- Uses millis() instead of delay() for timing, so the board keeps reading the tilt sensor while it counts.
- When all six LEDs are lit (one hour), the row clears and the count starts over.
- Tilting the board resets the timer.
What I tried after
- Reprogrammed the LEDs to flash in the rhythm of the Jingle Bells chorus.
- Changed the time periods to see how the timer behaved at different intervals.
- Reworked the reset so it runs without the tilt sensor, making the timer fully automatic.
Arduino, C++, Breadboard prototyping
View the timer code
interval_timer.ino
const int switchPin = 8;
unsigned long previousTime = 0;
int switchState = 0;
int prevSwitchState = 0;
int led = 2;
unsigned long interval = 600000; // 10 minutes per LED
void setup() {
for (int x = 2; x < 8; x++) {
pinMode(x, OUTPUT);
}
pinMode(switchPin, INPUT);
}
void loop() {
unsigned long currentTime = millis();
// Every interval, light the next LED.
if (currentTime - previousTime > interval) {
previousTime = currentTime;
digitalWrite(led, HIGH);
led++;
// After the sixth LED, clear the row and start over.
if (led == 8) {
delay(1000);
for (int x = 2; x < 8; x++) {
digitalWrite(x, LOW);
}
led = 2;
previousTime = millis();
}
}
// Tilting the board (tilt sensor on pin 8) resets the timer.
switchState = digitalRead(switchPin);
if (switchState != prevSwitchState) {
for (int x = 2; x < 8; x++) {
digitalWrite(x, LOW);
}
led = 2;
previousTime = currentTime;
}
prevSwitchState = switchState;
}
View the Jingle Bells code
jingle_bells_lights.ino
const int beat = 350; // Smaller = faster
// Relative note lengths for the chorus.
// 0 marks a pause between phrases.
const int rhythm[] = {
1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 4, 0,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 0,
1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 4, 0,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4
};
void setLights(int state) {
for (int pin = 2; pin <= 7; pin++) {
digitalWrite(pin, state);
}
}
void setup() {
for (int pin = 2; pin <= 7; pin++) {
pinMode(pin, OUTPUT);
}
}
void loop() {
int count = sizeof(rhythm) / sizeof(rhythm[0]);
for (int i = 0; i < count; i++) {
if (rhythm[i] == 0) {
setLights(LOW);
delay(beat);
} else {
int duration = rhythm[i] * beat;
setLights(HIGH);
delay(duration * 3 / 4);
setLights(LOW);
delay(duration / 4);
}
}
delay(1500); // Pause before repeating
}