hai dhenry ..
i'm sorry i have just read your reply, but actually, i can't understand about your answer, it cause i'm just a nubi on electronically ..
can you give me more explanation?
well,,
the next question is, can i put 12 ldr on my arduino board without breakout board or another additional board??
i have just read this link http://learn.adafruit.com/photocells/using-a-photocell but i have not yet solve the problem, why my ldr value always give me a "zero value" ??
and here's the code
int photocellPin = 2; // the LDR and cap are connected to pin2
int photocellReading; // the digital reading
int ledPin = 13; // you can just use the 'built in' LED
void setup(void) {
// We'll send debugging information via the Serial monitor
Serial.begin(9600);
pinMode(ledPin, OUTPUT); // have an LED for output
}
void loop(void) {
// read the resistor using the RCtime technique
photocellReading = RCtime(photocellPin);
if (photocellReading == 30000) {
// if we got 30000 that means we 'timed out'
Serial.println("Nothing connected!");
} else {
Serial.print("RCtime reading = ");
Serial.println(photocellReading); // the raw analog reading
// The brighter it is, the faster it blinks!
digitalWrite(ledPin, HIGH);
delay(photocellReading);
digitalWrite(ledPin, LOW);
delay(photocellReading);
}
delay(100);
}
// Uses a digital pin to measure a resistor (like an FSR or photocell!)
// We do this by having the resistor feed current into a capacitor and
// counting how long it takes to get to Vcc/2 (for most arduinos, thats 2.5V)
int RCtime(int RCpin) {
int reading = 0; // start with 0
// set the pin to an output and pull to LOW (ground)
pinMode(RCpin, OUTPUT);
digitalWrite(RCpin, LOW);
// Now set the pin to an input and...
pinMode(RCpin, INPUT);
while (digitalRead(RCpin) == LOW) { // count how long it takes to rise up to HIGH
reading++; // increment to keep track of time
if (reading == 30000) {
// if we got this far, the resistance is so high
// its likely that nothing is connected!
break; // leave the loop
}
}
// OK either we maxed out at 30000 or hopefully got a reading, return the count
return reading;
}
