Hvad gør den, hvad gør den ikke? Og hvorfor bruge en diode til det? Lys sensore er meget billige.
Er lidt nemmere at se på hvis du bruger
knappen
//
// This example shows one way of using an LED as a light sensor.
// You will need to wire up your components as such:
//LED #1:
// + digital2 (N side)
// |
// <
// > 100 ohm resistor
// <
// |
// |
// -----
// / \ LED #1, 5mm, clear plastic is good (or translucent green lense)
// -----
// |
// |
// + digital3 (P side)
//
//////////////////////////////////
//LED #2 (only required if you don't have the on-board LED on pin 13):
// + digital13 (P side)
// |
// |
// -----
// / \ LED #2
// -----
// |
// |
// + Ground
//
// What we are going to do is apply a positive voltage at digital2 and
// a low voltage at digital3. This is backwards for the LED, current will
// not flow and light will not come out, but we will charge up the
// capacitance of the LED junction and the Arduino pin.
//
// Then we are going to disconnect the output drivers from digital2 and
// count how long it takes the stored charge to bleed off through the
// the LED. The brighter the light, the faster it will bleed away to
// digital3.
//
// Then just to be perverse we will display the brightness back on the
// same LED by turning it on for a millisecond. This happens more often
// with brighter lighting, so the LED is dim in a dim room and brighter
// in a bright room. Quite nice.
//
//
#define LED1_N_SIDE 1 // original code uses pin 2
#define LED1_P_SIDE 2 // original code uses pin 3
#define LED2 13 // LED 2 is on-board or external on pin 13 and ground
//
// -1 = very dark ; 1 = very bright
int extreme = 0;
//
void setup()
{
pinMode(LED1_N_SIDE, OUTPUT); // N side is output or input but starts w/ output
pinMode(LED1_P_SIDE, OUTPUT); // P side is alway output pin (drive low or high)
pinMode(LED2, OUTPUT);
}
//
void loop()
{
unsigned int waitDischarge, extenLimit;
//
// Apply reverse voltage, charge up the pin and led capacitance
digitalWrite(LED1_N_SIDE,HIGH);
digitalWrite(LED1_P_SIDE,LOW);
delay(30);
//
// Isolate the pin 2 end of the diode
pinMode(LED1_N_SIDE,INPUT);
digitalWrite(LED1_N_SIDE,LOW); // turn off internal pull-up resistor
//
// Turn LED on if ambient light is very dark or medium
if (extreme <= 0) {
digitalWrite(LED2,HIGH);
}
//
// Count how long it takes the diode to bleed back down to a logic zero
for ( waitDischarge = 0; waitDischarge < 65534; waitDischarge++) {
if ( digitalRead(LED1_N_SIDE)==0) {
// very dark (you might need to sligthly change this number depending
// on the color of the lense of LED #1 for example)
if ( waitDischarge > 6 ) extreme = -1;
// very bright (you might need to sligthly change this number depending
// on the color of the lense of LED #1 for example)
else if ( waitDischarge < 3 ) extreme = 1;
else extreme = 0;
break;
}
delay(30); // to avoid going above 65534
}
//
// Turn LED off if ambient light is very bright or medium
if (extreme >= 0) digitalWrite(LED2,LOW);
delay(200);
}
