Keyestudio ARDUINO maker learning kit, Руководство пользователя

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Experiment principle
When it's approaching a fire, the voltage value the analog port reads differs. If you use a
multimeter, you can know when there is no fire approaching, the voltage it reads is around 0.3V;
when there is fire approaching, the voltage it reads is around 1.0V, tthe nearer the fire, the higher
the voltage.
So in the beginning of the program, you can initialize voltage value i (no fire value); Then,
continuously read the analog voltage value j and obtain difference value k=j-i; compare k with
0.6V (123 in binary) to determine whether or not there is a fire approaching; if yes, the buzzer will
buzz.
Sample program
//////////////////////////////////////////////////////////
int flame=0;// select analog pin 0 for the sensor
int Beep=9;// select digital pin 9 for the buzzer
int val=0;// initialize variable
void setup()
{
pinMode(Beep,OUTPUT);// set LED pin as “output”
pinMode(flame,INPUT);// set buzzer pin as “input”