Arduino calculating the frequency - what am I doing wrong here? - arduino

Question

I'm a newbie when it comes to electronics and Arduino - so the best way is to just to play around with it, right?
I have started a small project that utilize and LDR (Light Density Resistor) and want to use it to calculate the frequency that a light beam is blocked or turned off.
For debugging purposes I setup a small LED that blinks at a defined frequency (5 Hz etc.) and use a LCD to display the output.
I have a problem with my top right corner... It seems as it performs wrongly. It was the intention that it should show the registered frequency, but while debugging I have set it to show the number of counts in an interval of 5 sec (5,000 msec). But it appears as 24 is the max no matter what frequency I set (When I get it to show the right number [5 sec x 5 Hz = 25] I will divide by the time interval and get the results in Hz). It also shows 24.0 for 9 Hz etc..
I also have this: YouTube video
...but some fumbling in the beginning caused the LED to move a bit so it counted wrong. But in the end it "works".. But the 24.0 keeps being constant
This is my code:
#include <LiquidCrystal.h>
LiquidCrystal lcd(7, 8, 9, 10, 11 , 12);
int booBlocked = 0;
int counter = 0;
int checkValue = counter + 1;
int ledPin = 3; // LED connected to digital pin 3
int value = LOW; // previous value of the LED
long previousMillis = 0; // will store last time LED was updated
long freqency = 5; // Hz (1/sec)
long thousand = 1000;
long interval = thousand / freqency; // milliseconds
//long interval = 59; // interval at which to blink (milliseconds)
int tValue = 0; // Threshold value used for counting (are calibrated in the beginning)
long pMillis = 0;
long inter = 5000;
int pCount = 0;
float freq = 0; // Calculated blink frequency...
void setup() {
lcd.begin(16, 2);
lcd.setCursor(0,1); lcd.print(interval);
lcd.setCursor(4,1); lcd.print("ms");
pinMode(ledPin, OUTPUT); // sets the digital pin as output
lcd.setCursor(0,0); lcd.print(freqency);
lcd.setCursor(4,0); lcd.print("Hz");
}
void loop() {
// Print LDR sensor value to the display
int sensorValue = analogRead(A0);
lcd.setCursor(7,1);
lcd.print(sensorValue);
delay(100);
if (millis() > 5000){
doCount(sensorValue);
updateFreq();
lcd.setCursor(7+5,0);
lcd.print(freq);
} else {
setThresholdValue(sensorValue);
lcd.setCursor(7+5,1);
lcd.print(tValue);
}
// LED BLINK
if (millis() - previousMillis > interval) {
previousMillis = millis(); // remember the last time we blinked the LED
// if the LED is off turn it on and vice-versa.
if (value == LOW)
value = HIGH;
else
value = LOW;
digitalWrite(ledPin, value);
}
}
void updateFreq(){
long now = millis();
long t = now - pMillis;
if (t >= 10000) {
freq = (float) (counter - pCount);
//freq = ((float) (counter - pCount)) / (float) 10.0;
pMillis = now; // remember the last time we blinked the LED
pCount = counter;
}
}
void setThresholdValue(int sensorValue){
if (sensorValue > int(tValue/0.90)){
tValue = int (sensorValue*0.90);
}
}
void doCount(int sensorValue){
// Count stuff
if (sensorValue < tValue){
booBlocked = 1;
//lcd.setCursor(0,0);
//lcd.print("Blocked");
} else {
booBlocked = 0;
//lcd.setCursor(0,0);
//lcd.print(" ");
}
if (booBlocked == 1) {
if (counter != checkValue){
counter = counter + 1;
lcd.setCursor(7,0);
lcd.print(counter);
}
} else {
if (counter == checkValue){
checkValue = checkValue + 1;
}
}
}
UPDATE
A more "clean" code (please see my own answer)
#include <LiquidCrystal.h>
// Initiate the LCD display
LiquidCrystal lcd(7, 8, 9, 10, 11 , 12); // see setup at http://lassenorfeldt.weebly.com/1/post/2013/02/ardunio-lcd.html
long updateInterval = 150; // ms
long updateTime = 0;
// Declare the pins
int ledPin = 3; // LED connected to digital pin 3
// LED setup
int value = LOW; // previous value of the LED
long previousMillis = 0; // will store last time LED was updated
long freqency = 16; // Hz (1/sec)
long thousand = 1000;
long blinkInterval = thousand / freqency; // milliseconds
//// LDR counter variables ////
// Counting vars
static int counter = 0;
int booBlocked = 0;
int checkValue = counter + 1;
// Calibration vars
long onBootCalibrationTime = 5000; // time [time] to use for calibration when the system is booted
static int threshold = 0; // Value used for counting (calibrated in the beginning)
float cutValue = 0.90; // Procent value used to allow jitting in the max signal without counting.
// Frequency vars
float freq = 0; // Calculated blink frequency...
long frequencyInterval = 5000; // time [ms]
long pMillis = 0;
int pCount = 0;
void setup() {
// Setup the pins
pinMode(ledPin, OUTPUT); // sets the digital pin as output
// display static values
lcd.begin(16, 2);
lcd.setCursor(0,0); lcd.print(freqency);
lcd.setCursor(4,0); lcd.print("Hz");
lcd.setCursor(0,1); lcd.print(blinkInterval);
lcd.setCursor(4,1); lcd.print("ms");
// Setup that allows loggin
Serial.begin(9600); // Allows to get a readout from Putty (windows 7)
}
void loop() {
long time = millis();
int sensorValue = analogRead(A0);
// Blink the LED
blinkLED(time);
// Calibrate or Count (AND calculate the frequency) via the LDR
if (time < onBootCalibrationTime){
setThresholdValue(sensorValue);
} else {
doCount(sensorValue);
updateFreq(time);
}
// Update the LCD
if (time > updateTime){
updateTime += updateInterval; // set the next time to update the LCD
// Display the sensor value
lcd.setCursor(7,1); lcd.print(sensorValue);
// Display the threshold value used to determined if blocked or not
lcd.setCursor(7+5,1); lcd.print(threshold);
// Display the count
lcd.setCursor(7,0);
lcd.print(counter);
// Display the calculated frequency
lcd.setCursor(7+5,0); lcd.print(freq);
}
}
void blinkLED(long t){
if (t - previousMillis > blinkInterval) {
previousMillis = t; // remember the last time we blinked the LED
// if the LED is off turn it on and vice-versa.
if (value == LOW)
value = HIGH;
else
value = LOW;
digitalWrite(ledPin, value);
}
}
void setThresholdValue(int sValue){
if (sValue > int(threshold/cutValue)){
threshold = int (sValue*cutValue);
}
}
void doCount(int sValue){
if (sValue < threshold){
booBlocked = 1;
} else {
booBlocked = 0;
}
if (booBlocked == 1) {
if (counter != checkValue){
counter = counter + 1;
}
} else {
if (counter == checkValue){
checkValue = checkValue + 1;
}
}
}
void updateFreq(long t){
long inter = t - pMillis;
if (inter >= frequencyInterval) {
freq = (counter - pCount) / (float) (inter/1000);
pMillis = t; // remember the last time we blinked the LED
pCount = counter;
}
}
This code does not fix my question, but is just more easy to read.

Answer 1

The issue with your plan is that a light density resistor is going to pick up all the ambient light around and therefore be completely environment sensitive.
Have any other project hopes? This one seems like an engineering learning experience, not a coding one.
Have you thought of motor projects? Personally I'm more into home automation, but motor projects are almost instantly rewarding.

Answer 2

I'd recommend to re-write your doCount() function along these lines to make things simpler and easier to grasp:
void doCount(int sensorValue){
static int previousState;
int currentState;
if ( previousState == 0 ) {
currentState = sensorValue > upperThreshold;
} else {
currentState = sensorValue > lowerThreshold;
}
if ( previousState != 0 ) {
if ( currentState == 0 ) {
counter++;
}
}
previousState = currentState;
}
Let lowerThreshold and upperThreshold be, for example, 90% and 110%, respectively, of your former tValue, and you have a hysteresis to smoothen the reaction to noisy ADC read-outs.

Answer 3

I think i found one of the bugs.. I was using a delay() which caused some trouble..
I cleaned up the code:
#include <LiquidCrystal.h>
// Initiate the LCD display
LiquidCrystal lcd(7, 8, 9, 10, 11 , 12); // see setup at http://lassenorfeldt.weebly.com/1/post/2013/02/ardunio-lcd.html
long updateInterval = 150; // ms
long updateTime = 0;
// Declare the pins
int ledPin = 3; // LED connected to digital pin 3
// LED setup
int value = LOW; // previous value of the LED
long previousMillis = 0; // will store last time LED was updated
long freqency = 16; // Hz (1/sec)
long thousand = 1000;
long blinkInterval = thousand / freqency; // milliseconds
//// LDR counter variables ////
// Counting vars
static int counter = 0;
int booBlocked = 0;
int checkValue = counter + 1;
// Calibration vars
long onBootCalibrationTime = 5000; // time [time] to use for calibration when the system is booted
static int threshold = 0; // Value used for counting (calibrated in the beginning)
float cutValue = 0.90; // Procent value used to allow jitting in the max signal without counting.
// Frequency vars
float freq = 0; // Calculated blink frequency...
long frequencyInterval = 5000; // time [ms]
long pMillis = 0;
int pCount = 0;
void setup() {
// Setup the pins
pinMode(ledPin, OUTPUT); // sets the digital pin as output
// display static values
lcd.begin(16, 2);
lcd.setCursor(0,0); lcd.print(freqency);
lcd.setCursor(4,0); lcd.print("Hz");
lcd.setCursor(0,1); lcd.print(blinkInterval);
lcd.setCursor(4,1); lcd.print("ms");
// Setup that allows loggin
Serial.begin(9600); // Allows to get a readout from Putty (windows 7)
}
void loop() {
long time = millis();
int sensorValue = analogRead(A0);
// Blink the LED
blinkLED(time);
// Calibrate or Count (AND calculate the frequency) via the LDR
if (time < onBootCalibrationTime){
setThresholdValue(sensorValue);
} else {
doCount(sensorValue);
updateFreq(time);
}
// Update the LCD
if (time > updateTime){
updateTime += updateInterval; // set the next time to update the LCD
// Display the sensor value
lcd.setCursor(7,1); lcd.print(sensorValue);
// Display the threshold value used to determined if blocked or not
lcd.setCursor(7+5,1); lcd.print(threshold);
// Display the count
lcd.setCursor(7,0);
lcd.print(counter);
// Display the calculated frequency
lcd.setCursor(7+5,0); lcd.print(freq);
}
}
void blinkLED(long t){
if (t - previousMillis > blinkInterval) {
previousMillis = t; // remember the last time we blinked the LED
// if the LED is off turn it on and vice-versa.
if (value == LOW)
value = HIGH;
else
value = LOW;
digitalWrite(ledPin, value);
}
}
void setThresholdValue(int sValue){
if (sValue > int(threshold/cutValue)){
threshold = int (sValue*cutValue);
}
}
void doCount(int sValue){
if (sValue < threshold){
booBlocked = 1;
} else {
booBlocked = 0;
}
if (booBlocked == 1) {
if (counter != checkValue){
counter = counter + 1;
}
} else {
if (counter == checkValue){
checkValue = checkValue + 1;
}
}
}
void updateFreq(long t){
long inter = t - pMillis;
if (inter >= frequencyInterval) {
freq = (counter - pCount) / (float) (inter/1000);
pMillis = t; // remember the last time we blinked the LED
pCount = counter;
}
}
Its not as precise as I wished.. but I believe that this is might due to the way I blink the LED.
I also discovered that float cutValue = 0.90; has an influence... lowering the bar to 0.85 decrease the calculated frequency.. ??

Answer 4

I changed the code completely after Albert was so kind to help me out using his awesome FreqPeriodCounter library
I also added a potentiometer to control the frequency
Here is my code:
#include <FreqPeriodCounter.h>
#include <LiquidCrystal.h>
// FrequencyCounter vars
const byte counterPin = 3; // Pin connected to the LDR
const byte counterInterrupt = 1; // = pin 3
FreqPeriodCounter counter(counterPin, micros, 0);
// LCD vars
LiquidCrystal lcd(7, 8, 9, 10, 11 , 12); // see setup at http://lassenorfeldt.weebly.com/1/post/2013/02/ardunio-lcd.html
long updateInterval = 200; // ms
long updateTime = 0;
// LED vars
int ledPin = 5; // LED connected to digital pin 3
int value = LOW; // previous value of the LED
float previousMillis = 0; // will store last time LED was updated
static float freqency; // Hz (1/sec)
static float pfreqency;
static float blinkInterval; // milliseconds
boolean logging = true; // Logging by sending to serial
// Use potentiometer to control LED frequency
int potPin = 5; // select the input pin for the potentiometer
int val = 0; // variable to store the value coming from the sensor
void setup(void){
// Setup the pins
pinMode(ledPin, OUTPUT); // sets the digital pin as output
val = analogRead(potPin);
freqency = map(val, 0, 1023, 0, 25); // Hz (1/sec)
pfreqency = freqency;
blinkInterval = 1000 / (freqency*2); // milliseconds
// LCD display static values
lcd.begin(16, 2);
lcd.setCursor(0,0); lcd.print(freqency);
lcd.setCursor(4,0); lcd.print("Hz");
lcd.setCursor(14,0); lcd.print("Hz");
lcd.setCursor(0,1); lcd.print(blinkInterval);
lcd.setCursor(4,1); lcd.print("ms");
//
attachInterrupt(counterInterrupt, counterISR, CHANGE);
// Logging
if (logging) {Serial.begin(9600);}
}
void loop(void){
// Loop vars
float time = (float) millis();
float freq = (float) counter.hertz(10)/10.0;
// Blink the LED
blinkLED(time);
if (logging) {
if(counter.ready()) Serial.println(counter.hertz(100));
}
// Update the LCD
if (time > updateTime){
updateTime += updateInterval; // set the next time to update the LCD
lcdNicePrint(7+3, 0, freq); lcd.setCursor(14,0); lcd.print("Hz");
val = analogRead(potPin);
freqency = map(val, 0, 1023, 1, 30);
if (freqency != pfreqency){
pfreqency = freqency;
blinkInterval = 1000 / (freqency*2); // milliseconds
lcdNicePrint(0,0, freqency); lcd.setCursor(4,0); lcd.print("Hz");
lcd.setCursor(0,1); lcd.print(blinkInterval);
lcd.setCursor(4,1); lcd.print("ms");
}
}
}
void lcdNicePrint(int column, int row, float value){
lcd.setCursor(column, row); lcd.print("00");
if (value < 10) {lcd.setCursor(column+1, row); lcd.print(value);}
else {lcd.setCursor(column, row); lcd.print(value);}
}
void blinkLED(long t){
if (t - previousMillis > blinkInterval) {
previousMillis = t; // remember the last time we blinked the LED
// if the LED is off turn it on and vice-versa.
if (value == LOW)
value = HIGH;
else
value = LOW;
digitalWrite(ledPin, value);
}
}
void counterISR()
{ counter.poll();
}