Category: Digital

Here a simple arduino code for clock function without using RTC. If you only want to display the time and not the date, you do not need an RTC. The built-in crystal oscillator of the arduino is accurate enough for time displaying function.

Schematic Diagram

This is simple to build.

Code

[code lang=”c”]
// 1602 clock by tataylino.com
#include <LiquidCrystal.h>

LiquidCrystal lcd(7, 6, 5, 4, 3, 2);
int x = 0;
int minute = 1;
int hour = 12;
int sec = 0;
int am = 0; //1 = morning
bool up = false;
bool down = false;
bool display_update = true;
bool amtopm = false;

int backled = 9;
int button = 13;
int val = 0;
int aState;
int aLastState;

void setup() {
pinMode(button, INPUT);
pinMode(A2, INPUT);
pinMode(A3, INPUT);
// pinMode(13, OUTPUT);
pinMode(backled, OUTPUT);
analogWrite(backled, 255);
// set up the LCD’s number of columns and rows:
lcd.begin(16, 2);
lcd.setCursor(0, 0);
lcd.print(“Orasan”);

//set timer1 interrupt at 1Hz
TCCR1A = 0;// set entire TCCR1A register to 0
TCCR1B = 0;// same for TCCR1B
TCNT1 = 0;//initialize counter value to 0
// set compare match register for 1hz increments
OCR1A = 15624;// = (16*10^6) / (1*1024) – 1 (must be <65536)
// turn on CTC mode
TCCR1B |= (1 << WGM12);
// Set CS10 and CS12 bits for 1024 prescaler
TCCR1B |= (1 << CS12) | (1 << CS10);
// enable timer compare interrupt
TIMSK1 |= (1 << OCIE1A);
sei();//allow interrupts
}
void display() {
if(hour >= 10) {
lcd.setCursor(0, 2);
lcd.print(hour);
} else {
lcd.setCursor(0, 2);
lcd.print(“0”);
lcd.setCursor(1, 2);
lcd.print(hour);
}

lcd.setCursor(2, 2);
lcd.print(“:”);

if(minute >= 10) {
lcd.setCursor(3, 2);
lcd.print(minute);
} else {
lcd.setCursor(3, 2);
lcd.print(“0”);
lcd.setCursor(4, 2);
lcd.print(minute);
}

lcd.setCursor(5, 2);
lcd.print(“:”);
if(sec >= 10){
lcd.setCursor(6, 2);
lcd.print(sec);
} else {
lcd.setCursor(6, 2);
lcd.print(“0”);
lcd.setCursor(7, 2);
lcd.print(sec);
}
if(am == 1){
lcd.setCursor(8, 2);
lcd.print(“am”);
} else {
lcd.setCursor(8, 2);
lcd.print(“pm”);
}
}

void counting_time(){
if(minute < 0 ) {
minute = 59;
hour–;
}
if(hour < 1){ hour = 12; } if (sec >= 60) {
sec = 0;
minute++;
}
if (minute >= 60) {
hour++;
minute = 0;
}
if (hour >=13) {
hour = 1;
}
if(hour == 12 && minute == 0) { // to make sure only 1 am to pm transition
if(amtopm == true) {
amtopm = false;
if(am == 1){
am = 0;
} else {
am = 1;
}
}
}else{
amtopm = true;
}
}

ISR(TIMER1_COMPA_vect){//timer1 interrupt 1Hz
sec++;
counting_time();
if(display_update) {
display();
}
}

void loop() {
val = digitalRead(button); // read button
if (val == HIGH) {
//lcd.setCursor(0, 0);
//lcd.print(“o”);
//minute++;
//delay(500);
}
aState = digitalRead(A3);
if (aState != aLastState){
// If the outputB state is different to the outputA state, that means the encoder is rotating clockwise
if (digitalRead(A2) != aState) {
display_update = false;
minute ++;
counting_time();
if(minute >= 10) {
lcd.setCursor(3, 2);
lcd.print(minute);
} else {
lcd.setCursor(3, 2);
lcd.print(“0”);
lcd.setCursor(4, 2);
lcd.print(minute);
}
display_update = true;
} else {
display_update = false;
minute –;
counting_time();
if(minute >= 10) {
lcd.setCursor(3, 2);
lcd.print(minute);
} else {
lcd.setCursor(3, 2);
lcd.print(“0”);
lcd.setCursor(4, 2);
lcd.print(minute);
}
display_update = true;
}
}
aLastState = aState; //
}

[/code]

Just recently I made a project with arduino nano and used my old working board. To my surprise I got an error that the programmer is not responding. After some debugging I found out that there is no problem on my wires or drivers. It looks like arduino just updated their bootloader with no backward compatibility. There is not option on the board “ATmega328P ( Old Bootloader)” but it doesn’t work.

So I decided to just re-program my arduino nano with the latest bootloader. The bootloader hex file can be found on the directory below:

To program, I used power debugger and connected it like below:

After I programmed the latest bootloader, my arduino is alive again. 🙂

The real problem here is that arduino updated their bootloader with no backward compatibility. The best fix is to program your arduino board with the latest firmware that you can find on the arduino folder on your program files directory. You can use any AVR programmer. You can also use your working arduino to program another arduino here: https://www.arduino.cc/en/Tutorial/ArduinoISP

If you want to monitor a voltage level that is higher than the voltage that arduino input can handle, you will just need to use a voltage divider.

About the Circuit

Basically you will only need a voltage divider if you are measuring voltage that is greater than the max input voltage of your arduino.

“Vin” is where you will input the voltage to be measured. R1 and R2 forms a voltage divider to decrease voltage of the Vin. The value of R1 will be based on the max voltage that your Vin can reach.

Let R2 = 100k, you can choose higher value but check the computed value of R1 will be easy to find.

The maximum voltage that this arduino nano can handle is 5V so we will use that to compute for the value of R1. R1 is computed such that Va0 level is 5V at Maximum input voltage.

Computing for R1

For instance you are expecting the maximum input voltage is 15V, add about 10% to that to have a little headroom. So you will use 16.5V for your computation.

Vinmax = 16.5V
Va0max = 5V

R1 = (Vinmax – Va0max)/Iin

Iin = Va0max/R2

R1 = (R2(Vinmax – Va0max))/Va0max

R1 = R2((Vinmax/Va0max)-1)

replacing the value to the equation yields:

R1 = (100k)((16.5/5)-1)

R1 = 230k

Computing on software

Arduino will give you the digital value and not the actual voltage value so you need to compute and consider the voltage divider to be able to get the actual input voltage.

Actual voltage is computed as:

Vadc = (adc_val/adc_res)*adc_vref

where:

adc_val – digital value from the adc module
adc_res – ADC resolution, 1024 in case for arduino nano
adc_ref – ADC reference voltage. it is 5V default on arduino nano. This can be changed via program

And consider the voltage divider:

Va0 = Vin(R2/(R1+R2))

Vin = (Va0(R1+R2))/R2

Vin = (R1Va0 + R2Va0)/R2

Vin = Va0((R1/R2) + 1)

And since Va0 = Vadc then…

Vin = ( adc_vref(adc_val/adc_res))((R1/R2) + 1)

Now let’s put it into practice:

int adc_val;
int adc_ref;
int adc_res;
double Vin;
int R1;
int R2;

adc_ref = 5;
adc_res = 1024;
R1 = 230; //k
R2 = 100; //k

// read analog input

adc_val = analogRead(0);  // 0 = Connected to A0

Vin = (adc_ref(adc_val/adc_res))((R1/R2)+1);

Displaying it into the LCD

// include the library code:
#include <LiquidCrystal.h>// initialize the library with the numbers of the interface pins – The numbers
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);
int adc_val;
int adc_ref;
int adc_res;
double Vin;
int R1;
int R2;

void setup() {
adc_ref = 5;
adc_res = 1024;
R1 = 230; //k
R2 = 100; //k
    // set up the LCD’s number of columns and rows:
lcd.begin(16, 2);
   // Print a message to the LCD
lcd.print(“hello, world!”);
}

void loop() {
// read analog input
adc_val = analogRead(0);  // 0 = Connected to A0
Vin = (adc_ref(adc_val/adc_res))((R1/R2)+1);
// set the cursor to column 0, line 1
    // (note: line 1 is the second row, since counting begins with 0):
lcd.setCursor(0, 1);
    // print the number of seconds since reset:
lcd.print(“Voltage:”);
lcd.setCursor(1, 1);
lcd.print(Vin );

}

Related: CONNECTING ARDUINO NANO TO 16×2 LCD