Connecting the LEDs
Programming the LEDs and Timer
Connecting the Buzzer and Programming It
Adding the Reset Button and Connecting the Battery
You Are Done

Published July 19, 2018 © CC BY-NC-SA

Digital Hourglass Using PICO

This is an hourglass alarm that uses PICO, LEDs, and a buzzer to notify you when your time ends.

BeginnerFull instructions provided1 hour865

Things used in this project

Hardware components

PICO

LED (generic)

Buzzer

Resistor 1k ohm

Jumper wires (generic)

SparkFun Pushbutton switch 12mm

Breadboard (generic)

9V battery (generic)

Software apps and online services

Arduino IDE

Story

We all have started working on a project for an hour, only to end up working on it for three hours unknowingly. Today, we're going to fix this problem, and we'll do all of that in less than an hour!

We will create an alarm that uses LEDs and a buzzer to notify you when the time interval finishes. It will also have multiple checkpoints that keep you aware of how much time has passed. We'll be using PICO, LEDs, and a buzzer to get this done.

Connecting the LEDs

1 / 2 • The breadboard with the LEDs connected to the PICO

We want to have the LEDs either turned on or off, which means that they only need digital signal. Meaning that we can use the D0-D4 pins to control our 5 LEDs. And we connect them accordingly:

First of all, connect the anode - which is the positive longer leg - of each LED to the digital pins D0-D4 of PICO.

Now, connect the cathode - which is the negative shorter leg - to the GND.

connect a 330 ohm resistor in series between your PICO and each LED anode. We do this to protect our LEDs from exploding.

Now that we have the LEDs properly connected to our PICO, we have to program them to light up depending on the time passed, and that is what we are going to do in the next step.

Programming the LEDs and Timer

We want to create a program that turns on an LED after a certain amount of time has passed. Which means that we need variables that describe the following:

The time interval that we want to wait between changing the status of each LED

We will call it interval and it will be of the type long.

The last time an LED was changed

We will call it lastChange and it will be of the type unsigned long.

A variable for our LEDs

We will call it led and it will be of the type int.

A variable that describes the total time that the program has been running for

We will call it currentTime and it will be of the type unsigned long

The first thing we want to do is to relate our PICO's digital outputs to each of our led variables, and turn them all off. We used a for loop to do that and to avoid writing 10 lines of code, and only wrote 3 instead. In our void loop() function we assigned milis() to our currentTime variable then compared it to the last time an LED was changed, and to the interval that we wanted.

Connecting the Buzzer and Programming It

1 / 2 • The breadboard with the LEDs and buzzer connected to PICO

Now that we have our LEDs and their code ready. We are also going to add a buzzer that creates a noise to notify us when the time interval passes. Connecting the buzzer is very simple, as it can only be turned on or off, and we connect it to A1 to do so.

First of all, connect the anode - which is the positive longer leg - to PICO's A1

Then, connect the cathode - which is the negative shorter leg - to the GND

Now that our buzzer is connected to our PICO, lets code it so it starts buzzing when the time interval passes. We simply create a condition to check whether our last LED is turned on or not, and if it is, the buzzer makes a sound since the entire time interval has passed.

Adding the Reset Button and Connecting the Battery

1 / 2 • The breadboard with everything connected, and the wiring fixed

Our hourglass now alarms us when the time period finishes. But, we have to disconnect it and and reconnect it to the power source whenever we want to reset it, and that is impractical. So, lets add a push button that easily does that for us, and let's connect it to an external power source instead of having to use USB for power.

Push buttons are very simple, they only have two legs, and the orientation of the connection doesn't matter because push buttons don't have polarities. When the push button is unpressed "open", there is not connection between its two legs, meaning that there is no current flow. Pressing the button closes the connection between its legs, connecting them and allowing current to flow between them.

We will use this to connect it to PICO, and when current flows into PICO from the push button it is going to reset the LEDs and the timer.

Just one more turn

Do the following to connect our PICO to the 9v battery:

Connect the battery's positive pole to PICO's Vin

Connect PICO's Vout to the breadboard's positive power strip

Connect the battery's negative pole, to the breadboard's negative power strip

And you can turn on your PICO without having to connect it to a PC.

After we connected everything, lets rewire our project and make it look better and cleaner.

You Are Done!

The finished project

In this guide we have learned how to use PICO's built-in timer, and how to use push buttons. And, at the end, we created an awesome hourglass alarm that we can use to keep time, and that is great!

We will be more than happy to answer any questions, feel free to ask anything. :-)

unsigned long previousTime = 0;                           //variable which holds the time an LED was last changed.
int led;                                                  //variable that holds the led pin number, this variable will update in real-time running.

const long interval  60000                                   //the time interval 60000(1 min). Change this if you want to change the time period 

void setup() {

  for (led = 0 ; led <= 4 ; led++) {                       //set the 5 LEDs as an OUTPUTs, and turn them OFF using the for loop.
    pinMode(led, OUTPUT);
    digitalWrite(led, LOW);
  }

  led = 0;                                                 //update the led variable value to be 0.
}

void loop() {

  unsigned long currentTime = millis();                   //the amount of time the Arduino has been running with millis() and store it in currentTime variable.

  if ( (currentTime - previousTime) >= interval)         //if the time interval between to two events is greater than or equal 60000(1 min.) turn a single LED ON
  {
    previousTime = currentTime;
    digitalWrite(led, HIGH);
    led++;                                                //increment the led variable to be ready to turn ON the next LED.
  }

}

unsigned long previousTime = 0;                           //variable which holds the time an LED was last changed.
int led;                                                  //variable holds the led pin number, this variable will update in real-time running.

#define interval  60000                                   //the time interval 60000(1 min). Change this if you want to change the time period 
#define buzzer A1                                         //the pin which connected to the buzzer.

void setup() {

  for (led = 0 ; led <= 4 ; led++) {                       //set the 5 LEDs as an OUTPUTs, and turn them OFF using the for loop.
    pinMode(led, OUTPUT);
    digitalWrite(led, LOW);
  }
  
  led = 0;                                                 //update the led variable value to be 0.
  
  pinMode(buzzer, OUTPUT);                                 //set the buzzer as an OUTPUT Pin.
}

void loop() {

  unsigned long currentTime = millis();                   //the amount of time the Arduino has been running with millis() and store it in currentTime variable.

  if ( (currentTime - previousTime) >= interval)         //if the time interval between to two events is greater than or equal 60000(1 min.) turn the a single LED ON
  {
    previousTime = currentTime;
    digitalWrite(led, HIGH);
    led++;                                                //increment the led variable to be ready to turn ON the next LED.

    if (led == 5)                                         //if the fifth LED is ON turn ON the noisy buzzer.
      tone(buzzer, 500);
  }

}

unsigned long previousTime = 0;                           //variable which holds the time an LED was last changed.
int led;                                                  //variable holds the led pin number, this variable will update in real-time running.

#define interval  60000                                   //the time interval 60000(1 min). Change this if you want to change the time period 
#define switchPin  A0                                     //the pin which connected to the pushbutton.
#define buzzer A1                                         //the pin which connected to the buzzer.

void setup() {

  for (led = 0 ; led <= 4 ; led++) {                       //set the 5 LEDs as an OUTPUTs, and turn them OFF using the for loop.
    pinMode(led, OUTPUT);
    digitalWrite(led, LOW);
  }
  
  led = 0;                                                 //update the led variable value to be 0.
  
  pinMode(switchPin, INPUT);                               //set the switchPin as an INPUT Pin.
  pinMode(buzzer, OUTPUT);                                 //set the buzzer as an OUTPUT Pin.
}

void loop() {

  unsigned long currentTime = millis();                   //the amount of time the Arduino has been running with millis() and store it in currentTime variable.


  if ( (currentTime - previousTime) >= interval)         //if the time interval between to two events is greater than or equal 60000(1 min.) turn the a single LED ON
  {
    previousTime = currentTime;
    digitalWrite(led, HIGH);
    led++;                                                //increment the led variable to be ready to turn ON the next LED.

    if (led == 5)                                         //if the fifth LED is ON turn ON the noisy buzzer.
      tone(buzzer, 500);
  }

  int switchRead = digitalRead(switchPin);                //read the switch state and save the reading inside the switchRead variable.
  
  if (switchRead == HIGH)                                 //if the pushbutton is pressed turn OFF all the LEDs, turn OFF the buzzer, and reset the Timer.
  {
    for (int i = 0 ; i <= 4 ; i++)
    {
      digitalWrite(i, LOW);                               //turn OFF the LEDs.
    }
    noTone(buzzer);                                       //turn OFF the buzzer.
    led = 0;                                              //update the led value to start from point zero.
    previousTime = currentTime;
  }
}

Credits

MellBell Electronics

2 projects • 2 followers

We want to provide makers with great content, along with our products, to give them the ability to build anything they want.

Digital Hourglass Using PICO

Things used in this project

Hardware components

Software apps and online services

Story

Connecting the LEDs

Programming the LEDs and Timer

Connecting the Buzzer and Programming It

Adding the Reset Button and Connecting the Battery

You Are Done!

Code

LEDs and Timer Code

LEDs and Timer Code + Buzzer

The Final Code

Credits

MellBell Electronics

Comments

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Digital Hourglass Using PICO

Digital Hourglass Using PICO

Things used in this project

Hardware components

Software apps and online services

Story

Connecting the LEDs

Programming the LEDs and Timer

Connecting the Buzzer and Programming It

Adding the Reset Button and Connecting the Battery

You Are Done!

Code

LEDs and Timer Code

LEDs and Timer Code + Buzzer

The Final Code

Credits

MellBell Electronics

Comments

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