C++ buzzer to play piano notes for an Arduino - c++

unsigned long t;
boolean isHigh;
#define BUZZER_PIN 3
void setup() {
// put your setup code here, to run once:
pinMode(BUZZER_PIN, OUTPUT);
isHigh = false;
t = micros();
}
void loop() {
playNote('c');
}
void playNote(char note) {
unsigned long timeToWait;
unsigned long timeToPlayTheNote = millis();
while (timeToPlayTheNote - millis() < 1000) {
if (note == 'c') {
timeToWait = 1911;
}
if (micros() - t > timeToWait) {
if (!isHigh) {
digitalWrite(BUZZER_PIN, HIGH);
isHigh = true;
} else {
digitalWrite(BUZZER_PIN, LOW);
isHigh = false;
}
t = micros();
}
}
}
I don't know why this won't work. I used to play a frequency every 1,000 microseconds but is there any way to make this simpler as well? Also, with this method I have to do (1/f)/2 and then convert that value from seconds to microseconds and use that as the value for timeToWait.

Initialization of ˋtimeToWait` should obviously be outside of the loop.
An array could be used for timing data.
ˋt` should probably be initialized inside ˋplayNoteˋ
Alternatively, you might use an enum for delay associated to a note.
enum class notes
{
C = 1911
};
Well, all suggestion assume that you don't want to compensate for drifting offsets.

Buzzers have a fixed frequency. They don't work like speakers at all. You will get better results with a real speaker. Don't forget to put a capacitor in series with it so the speaker sees an AC signal, you can fry a speaker quite easily if you feed it a DC signal..
For best results, you should use 2 x 47uF to 100uF electrolytic capacitors back to back, with the negative poles joined together, one positive to the 'duino and the other positive pole connected to the speaker. With higher capacitance, you'll get more bass.
Why don't you use a PWM at 50% (128) and change the PWM frequency to generate the sound? You could use the Timer1 or Timer3 library for that. Letting the hardware do the work would be more presise and would free your application for other tasks, such as reading a keyboard.
https://playground.arduino.cc/Code/Timer1
Setting the PWM at 0% with an analogWrite() would cut the sound.

Related

How to make DC motor's RPM come to its maximum value (analog 255) SLOWLY

It is a homework and I have completely NO idea, my teacher says you need just while, analogWrite and a counter. I have a DC motor, a transistor and a 9V battery.
I know my code does NOTHING, but just as example.
int analogPin = 3;
int count = 0;
void setup()
{
pinMode(analogPin, OUTPUT);
}
void loop() {
while(count<30){
analogWrite(analogPin , 255);
delay(20000);
count++;
}
}
You need to use counter value as your analogue output value:
void loop()
{
if( count < 256 )
{
analogWrite( analogPin, count ) ;
delay( 20000 );
count++ ;
}
}
Note that you do not need a while loop; the Arduino framework already calls loop() iteratively (the clue is in the name). However if your teacher thinks you need one and is expecting one, you may need to use one just for the marks. Alternatively discuss it with your teacher, and explain why it is unnecessary
In fact the delay too is arguably bad practice - it is unhelpful in applications where the loop() must do other things while controlling the motor. The following allows other code to run whilst controlling the motor:
unsigned long delay_start = 0 ;
void loop()
{
if( count < 256 &&
millis() - delay_start >= 20000ul )
{
analogWrite( analogPin, count ) ;
count++ ;
delay_start = millis() ;
}
// Do other stuff here
}
Because the loop() now never blocks on the delay() function, you can have code that does other things such as read switch inputs and it can react to them instantly, whereas as in your solution, such inputs could be ignored for up-to 20 seconds!
A typical DC motor will not start moving at very low values - you may want to start count somewhat higher than zero to account for the "dead-band". Analogue signals are also generally a poor way to drive a DC motor and varying speed; a PWM is generally a more efficient method, and will allow the motor to run at lower speeds. With an analogue signal at low levels (lower than for PWM), your motor will not move and will just get warm and drain your battery.
For test purposes, reduce the delay time; you don't want to sit there for an hour and 25 minutes just to find the code does not work! Set it to say 500ms, then start it, time how long it takes before the motor starts to move. If that is say 30 seconds, then yu know the motor starts to move when count is about 60; in which case that is a better starting value that zero. Then you can increase your delay back to 20 seconds if you wish - though a DC power supply might be better than a battery - I'm not sure it will last that long.

Accelerometer vibration detection using a threshold

I've program the Accelerometer to detect vibrations by setting a reasonable min/max threshold along all 3-axis' raw data. I need it to only count how many times it detects vibration, however, due to the way it's programmed with the threshold, I used a delay of about 1 sec in order to prevent multiple miscounts, which works but interferes with the Ultrasonic Module (HC-SR04) when it needs to read distance values is synchronously with the Accelerometer. Would like to get some feedback on this.
As far as I understand, you are using Arduino's delay() function. Bad idea as you block the all the rest of your application, well, you noticed already...
Better approach just checking if some time elapsed, e. g. using millis function:
static bool isDelay = false;
static unsigned long timestamp;
if(detect())
{
isDelay = true;
timestamp = millis();
}
if(isDelay && millis() - timestamp > 1000)
{
isDelay = false;
}
if(!isDelay)
{
// actions to be taken...
}
Always use subtraction between the timestamp and the current time – the time counter might overflow, subtraction result is unaffected, though, and you are safe...
You can simply skip the isDelay variable if you are sure enough that the relevant event always occurs at least once in between overflow period (around 50 days):
static unsigned long timestamp = millis() - 1000;
if(detect())
{
timestamp = millis();
}
if(millis() - timestamp > 1000)
{
// actions to be taken...
}
Both variants: static variables as assuming you have this code in Arduino's loop function (or one being called from loop). Yet prefer replacing the magic number 1000 with a macro and you're fine...

Arduino Buzzer for Knock Knock project is not working

Im trying to generate a knock knock detector using Arduino and a Piezo Buzzer. The one used in this proyect is the same as in this picture
Using this code
const int outputPin = 8; // led indicator connected to digital pin
const int knockSensor = A0; // the piezo is connected to an analog pin
const int thresholdHIGH =150; // threshold value to decide when the detected knock is hard (HIGH)
const int thresholdLOW = 120; // threshold value to decide when the detected knock is gentle (LOW)
const int secretKnockLength = 4; //How many knocks are in your secret knock
/* This is the secret knock sequence
* 0 represents a LOW or quiet knock
* 1 represents a HIGH or loud knock
* The sequence can be as long as you like, but longer codes increase the difficulty of matching */
const int secretKnock[secretKnockLength] = {0, 0, 1, 0};
int secretCounter = 0; //this tracks the correct knocks and allows you to move through the sequence
int sensorReading = 0; // variable to store the value read from the sensor pin
void setup() {
//Set the output pin as an OUTPUT
pinMode(outputPin, OUTPUT);
//analogWrite(knockSensor, LOW);
//Begin Serial Communication.
Serial.begin(9600);
}
void loop() {
// read the piezo sensor and store the value in the variable sensorReading:
sensorReading = analogRead(knockSensor);
Serial.print ("Valor del Sensor: ");
Serial.println(sensorReading);
// First determine is knock if Hard (HIGH) or Gentle (LOW)
//Hard knock (HIGH) is detected
if (sensorReading >= thresholdHIGH) {
//Check to see if a Hard Knock matches the Secret Knock in the correct sequence.
if (secretKnock[secretCounter] == 1) {
//The Knock was correct, iterate the counter.
secretCounter++;
Serial.println("Correct");
} else {
//The Knock was incorrect, reset the counter
secretCounter = 0;
Serial.println("Fail");
digitalWrite(outputPin, LOW);
}//close if
//Allow some time to pass before sampling again to ensure a clear signal.
delay(100);
//Gentle knock (LOW) is detected
} else if (sensorReading >= thresholdLOW) {
//Check to see if a Gentle Knock matches the Secret Knock in the correct sequence.
if (secretKnock[secretCounter] == 0) {
//The Knock was correct, iterate the counter.
secretCounter++;
Serial.println("Correct");
} else {
//The Knock was incorrect, reset the counter.
secretCounter = 0;
Serial.println("Fail");
}//close if
//Allow some time to pass before sampling again to ensure a clear signal.
delay(100);
}//close if else
//Check for successful entry of the code, by seeing if the entire array has been walked through.
if (secretCounter == (secretKnockLength) ) {
Serial.println("Welcome");
//if the sececret knock is correct, illuminate the LED for a couple seconds
digitalWrite(outputPin, HIGH);
//Reset the secret counter to 0.
secretCounter = 0;
}//close success check
}//close loop".
My problem is the buzzer is detecting nothing. I dont know if this is because the buzzer is not the correct one or something else.
Any idea?
If the problem is that the buzzer isn't making any noise, then you should be using the tone() function in your code. (https://www.arduino.cc/reference/en/language/functions/advanced-io/tone/)
Your code compiles successfully, so if that's not your issue, then there's probably something wrong with your project's wiring.
To detect knocking, you need to use piezo without driver circuit.
according to Arduino tutorial said that avoid piezo with plastic housing.
You should use piezo that look like metal disc like this
(image from sparkfun)
Note : piezo with plastic housing might contain drive circuit or not piezo at all (it might be magnetic buzzer)

For loop with if statement for ardiuno powered humidity control

Really simple question but I'm not entirely sure how to incorporate a for loop in the if statement I have. Context: I have a humidifier I am trying to automate based on the humidity of the room. I'm using an ardiuno, dht11 humidity sensor and a servo. The humidifier knob has three settings (high low off) and so the servo has three positions. I have the code running so the servo turns appropriately according to the humidity level. The issue is that it fluctuates very easily. To correct that I'm looking to incorporate a for loop so that after let say 60 one second iterations of the humidity being greater than 55 the servo moves. I tried to add a for loop but it doesn't seem to be working.
But this is only my solution based on the little programming I know. If there is a better solution or even an equally viable alternative I'd love to know. I'm currently studying mechanical engineering but I'm finding that to really make something one needs a background in electronics and code. I'm trying to learn both independently through a series of projects and so I'm quite eager to learn. Hopefully this helps explain why I'm asking such a simple questions to begin with.
#include <dht.h>
#include <Servo.h>
Servo myservo;//create servo object to control a servo
dht DHT;
#define DHT11_PIN 7 // pin for humidity sensor ( also measure temp)
void setup() {
myservo.attach(9);//attachs the servo on pin 9 to servo object
myservo.write(0);//statting off position at 0 degrees
delay(1000);//wait for a second
Serial.begin(9600);
}
void loop() {
int chk = DHT.read11(DHT11_PIN); // the follow is just so that I can see the readings come out properly
Serial.print("Temperature = ");
Serial.println(DHT.temperature);
Serial.print("Humidity = ");
Serial.println(DHT.humidity);
delay(500);
if (DHT.humidity > 55) // here is where my code really begins
{
for (int i=0; i>60; i++); // my goal is to execute the follow code after the statement above has been true for 60 one second iterations
{
myservo.write(0);//goes to off position
delay(1000);//wait for a second
}
} else if (DHT.humidity > 40 ) {
for (int i=0; i>60; i++); // same thing here
myservo.write(90);//goes to low position
delay(1000);//wait for a second
}
else
{
for (int i=0; i>60; i++);
myservo.write(180);//goes to high position
delay(1000);
}
} // end of void loop()
Just addressing your question, the following line is incorrect:
for (int i=0; i>60; i++);
Two things:
1) The second statement in the for loop describes the conditions on which it executes. The way it is written, it will only execute when i>60 (not what you want according to the comments).
2) The semicolon after the for statement makes the next block unassociated.
Correct that line to the following:
for (int i=0; i<60; i++)
See the following for more information:
https://www.tutorialspoint.com/cprogramming/c_for_loop.htm
It would probably be helpful to examine your compiler warnings, and/or set a higher warning level, to catch these type of things early (this is, of course, somewhat compiler dependent).
I guess you trying kind of de-bouncing at you need humid level stay in same range for some period.
First, I define conversion function to map humid level to state
#define HUMID_OFF 1
#define HUMID_LOW 2
#define HUMID_HIGH 3
byte state_conv (float humid_level){
if (humid_level > 55) return HUMID_OFF ;
else if (humid_level > 40 ) return HUMID_LOW ;
else return HUMID_HIGH ;
}
Second I will check changing of state and use millis() to count time while current state is steady. if counting time are longer than threshold then change the actual state.
/*Global variable*/
byte actual_state;
byte flag_state;
void setup (){
// Do things that necessary
float humid = dht.readHumidity();
/*Initialize value*/
actual_state = state_conv(humid);
flag_state= state_conv(humid);
}
void loop(){
static unsigned long timer = millis();
float humid = dht.readHumidity();
byte crr_state = state_conv(humid);
if (crr_state != actual_state ){// if state is changing
if (flag_state != crr_state){
/if crr_state change form last iteration then reset timer
flag_state = crr_state;/
timer = millis();
}
else if (millis() - timer > 10000){
//if crr_state not change for 10000 ms (10 second)
actual_state = crr_state; // update actual state to crr_state
}
}
// After this use actual_state to control servo
if (actual_state == HUMID_OFF ){
myservo.write(0);//goes to off position
}
else if (actual_state == HUMID_LOW ){
myservo.write(90);//goes to low position
}
else if (actual_state == HUMID_HIGH ){
myservo.write(180);//goes to high position
}
}
DHT.humidity returns a float, so if you want to compare, then first store this in an int, and then compare.

Arduino interrupt frequency

I am using an Arduino uno to measure the speed of a dc motor.
I have a opto sensor that gives a pulse when the motor has made a full turn.
The problem I've got starts when the motor has a speed > 90Hz.
As soon as I reach 90Hz, the Arduino doesn't enter the interrupt function.
My code:
int pin = 13;
volatile int state = LOW;
volatile unsigned long startTijd = 0;
volatile unsigned long eindTijd = 0;
unsigned int frequentie = 0;
volatile int count = 0;
void setup()
{
pinMode(pin, OUTPUT);
attachInterrupt(0, blink, FALLING); //LOW, HIGH, FALLING, RISING, CHANGE
Serial.begin(19200);
}
void loop()
{
noInterrupts();
digitalWrite(pin, state);
interrupts();
}
void blink()
{
if (count == 0) {
startTijd = micros();
}
count++;
if (count == 31) {
count = 0;
eindTijd = micros();
eindTijd -= startTijd;
Serial.print(eindTijd);
Serial.print(" ms. - ");
frequentie = 30 * 1000000 / eindTijd;
Serial.print(frequentie);
Serial.println(" Hz.");
}
state = !state;
}
My question is : When the Arduino receives interrupts at 90Hz, it doesn't execute the code in the interrupt. When the motor goes below 90Hz after that, the code works again. What am I doing wrong ?
It looks as though blink is your ISR. If that's the case, you shouldn't be doing debug I/O within that routine for 2 reasons. The first is that you are calling a process that could block. The second is that ISRs should do their thing and finish (should be highly efficient). My guess is that if you remove the debug I/O from your ISR and pass info back to the interrupted task instead (safely, of course) you will be able to service interrupts at greater than 90 hz.
Just to add to #Bruce answer. You are using serial IO in the interrupt. Each time you are printing around 15-20 characters (depending on the values calculated). Each character is encoded by 8 bit data + 1 start bit + 1 stop bit = 10 bits. So, say 20*10=200 bits. The baud rate is 19200bps, so time required to transmit 200 bits is 200/19200 sec, or in terms of frequency 19200/200=96Hz. So this is the maximum frequency achievable for transmission of 20 characters, which is close to your measured 90Hz (take in account that I am not considering any time spacing overhead between the transmits).