Tuesday, January 1, 2019

How to blow an LED like a candle – LED as a temperature sensor

We’ve seen before how an LED can be used as a light sensor that senses how much light on it and then it can respond to this light intensity as a sensor and then reading this response with an Arduino.

Today we are checking this cool project of using Arduino with an LED as a temperature sensor that senses when it has been blow at and turns on and off.

What you need

Arduino

LED

220 ohm resistor

Some small wires

Circuit connection

Software

// Blow Out LED Ave creates an LED that you can blow out. It automatically relights after 2 seconds
//
// Copyright 2018, Paul H. Dietz

// LED Connections
#define PLUS A1 // High side of the resistor
#define MEASURE A0 // Low side of resistor and anode of LED
// Cathode of LED goes to ground

#define NUMSAMPLES 10 // Number of samples to keep
#define MINJUMP 150 // Minimum jump for blow out

long int sensedata[NUMSAMPLES];
int dataptr = 0;
int buffull = 0;

void setup() {
Serial.begin(250000); // Initialize serial communication
pinMode(MEASURE, INPUT);
pinMode(PLUS, OUTPUT);
digitalWrite(PLUS, HIGH); // Turn on the LED
}

void loop() {
int cnt;
long int sum = 0;

// Sum 256 adc readings (to reduce adc noise)
for (cnt = 0; cnt < 256; cnt++) {
sum = sum + analogRead(MEASURE);
}

Serial.println(sum); // Output sum so we can watch with Serial Plotter

// Compare current measurement to oldest if buffer full
if (buffull && (sum > (sensedata[dataptr] + MINJUMP))) {
// Temperature drop exceeded minimum - turn off
digitalWrite(PLUS, LOW);
dataptr = 0; // Reinitialize the buffer
buffull = 0;
delay(2000); // off time for LED
digitalWrite(PLUS, HIGH);
}
else {
sensedata[dataptr] = sum; // Store the latest data in the buffer
dataptr++; // Update buffer pointer
if (dataptr == NUMSAMPLES) { // Check if dataptr went past end
dataptr = 0; // Reset the dataptr to beginning
buffull = 1; // Mark that buffer is full
}
}

}

Testing