Hey all. I have a circuit that I'm pretty stumped on. I'm a novice working on a project way over my head (but am so close!)
I'm trying to have a piezo sensor activate an LED strip using an Arduino Mega. My circuit is more complex than what I'm showing above, but I believe this is the problem area. It's really just this circuit repeated a number of times with different arduino pins.
The LED strip takes 12v, and has each set of lights in parallel with resistors built in (I'm showing 100ohm as a placeholder, not sure what it actually is). The current is about 3 amps. The trouble arises only when 12v is connected to the circuit and the LEDs are on. When the 12v is disconnected (and only 5v is connected from the USB), all LEDs are off, and I get a nice consistent reading when I tap the piezo. When I have the 12v connected and the LEDs set to LOW in my program, still nothing out of the ordinary (no readings). As soon as I set the LEDs to any value higher than 0, the Piezo actually starts buzzing quietly and the analog input pin gives me rapid very high readings. It's as if the load from the LEDs is partially sinking through the Piezo and into the analog in! Is this possible?
In an attempt to stop that from happening, I placed a 10uF capacitor between the negative side of the Piezo and ground. Same results.
Is there another component I need in the mix, or a change in my circuit? Any help is greatly appreciated!
Here is my test code in case this helps:
const int redPin = 5;
const int greenPin = 6;
const int bluePin = 7;
const int knockSensor1 = A0; // the piezo is connected to analog pin 0
const int threshold = 150; // threshold value to decide when the detected sound is a knock or not
float r = 0;
float g = 0;
float b = 0;
boolean fireR = false;
boolean fireG = false;
int countdown = 0;
int sensorReading1 = 0; // variable to store the value read from the sensor pin
int c=0;
void setup() {
pinMode(greenPin, OUTPUT);
pinMode(redPin, OUTPUT);
pinMode(bluePin, OUTPUT);
analogWrite(greenPin, 0);
analogWrite(redPin, 0);
analogWrite(bluePin, 0);
Serial.begin(9600); // use the serial port
}
void loop() {
// read the sensor and store it in the variable sensorReading:
sensorReading1 = analogRead(knockSensor1);
///Serial.println(sensorReading);
// if the sensor reading is greater than the threshold:
if (sensorReading1 >= threshold) {
//pick random color
r = random(255);
g = random(255);
b = random(255);
analogWrite(redPin, r);
analogWrite(greenPin, g);
analogWrite(bluePin, b);
Serial.println();
Serial.println();
Serial.println("FIRE! ");
Serial.println(sensorReading1);
Serial.println();
}
delay(5); // delay to avoid overloading the serial port buffer
}
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