const int ledPin = LED_BUILTIN;
int ledState = LOW;
unsigned long previousMillis = 0; // will store last time LED was updated

// constants won't change:
const long interval = 50;........

command to blink output pin...which is output for tone same......to pulse/blink  50ms on same output pin...........looking  or should I say sounding good now......like a dirt bike...lol

I hard audio noises...  No video...

It might be better to use a 555 timer Oscillator changing the pitch s the RPM goes Up/Down...

// Useing Nano Tachometer
//-------------------------------------
#include <Wire.h>
//#include "Adafruit_LEDBackpack.h"

// External interrpt pin for sensor
#define interruptPin 2

//Adafruit_7segment matrix = Adafruit_7segment();

long lastUpdate = 0; // for timing display updates
volatile long accumulator = 0; // sum of last 8 revolution times
volatile unsigned long startTime = 0; // start of revolution in microseconds
volatile unsigned int revCount = 0; // number of revolutions since last display update

//-------------------------------------
// Setup - runs once at startup
//-------------------------------------
void setup()
{
// Initialize the serial port and display
Serial.begin(115200);
//matrix.begin(0x70);

// Enable the pullup resistor and attach the interrupt
pinMode(interruptPin, INPUT_PULLUP);
attachInterrupt(digitalPinToInterrupt(interruptPin), tach_interrupt, FALLING);
}

//-------------------------------------
// Main Loop - runs repeatedly.
// Calculate RPM and Update LCD Display
//-------------------------------------
void loop()
{


if (millis() - lastUpdate > 1000) // update every second
{
unsigned int rpm = 0;
// divide number of microseconds in a minute, by the average interval.
if (revCount > 0)
{
rpm = 6000000 / (accumulator>>2);
}

Serial.println(rpm);
int sensorReading = (rpm);

int thisPitch = map(sensorReading, 0, 17, 31, 38);

// play the pitch:
tone(9, thisPitch, 1150);
//tone(10, thisPitch, 1050);
delay(1); // delay in between reads for stability
//matrix.println(rpm);
//matrix.writeDisplay();

lastUpdate = millis();
revCount = 0;
}
}

//-------------------------------------
// Interrupt Handler
// Magnetic sensor - target passed
// Calculate revolution time
//-------------------------------------
void tach_interrupt()
{
// calculate the microseconds since the last interrupt
long usNow = micros();
long elapsed = usNow - startTime;
startTime = usNow; // reset the clock

// Accumulate the last 8 interrupt intervals
accumulator -= (accumulator >> 2);
accumulator += elapsed;
revCount++;
}

Randy (MC2)

Looks like it needs more experimentation...  maybe a special workbench setup with a motor hooked up, etc. so you could easily make changes and get quick results...  Like maybe have more Markers around the rim and measure Time from one marker to the next... calc. rpm from the time...  All markers would have to be equidistant from each other...  maybe divide the cicumference by 10 for 10 markers and go from there?

How are you going to drive the Speaker for the sound of the Card?

Thanks for keeping us updated.

How are you controlling the speaker? I would assume through a gpio pin, correct?  If that's the case then you could use a PWM IO pin and map the RPM input into a PWM out (0-255) via a map & constrain pair and then that value to an analogWrite to set the PWM.  

Sounds like a fun project :)

Scott

Thanks,  Randy