user62121: I’ve been trying to make this project: https://create.arduino.cc/projecthub/chummer1010/electronic-safe-with-arduino-25d039
I’m confident that I’ve assembled everything correctly, but my LCD doesn’t display characters. Other projects seem to have fixed it by changing the potentiometer but I’m not using one. 
Arduino code:
/* 
Made by Marco Fusco
May 20, 2016
Contact me at: marcofusco111@gmail.com
*/


#include <LiquidCrystal.h>
#include <EEPROM.h>
#include <Servo.h>

int address = 0;
static unsigned long SaveTimer;
static unsigned long SaveDelay = (30 * 1000); 


char CODE[10] = "1234E"; 
char Str[10]; 
char CodeLength = 4;
int Pos = 0;
bool Unlocked;
static unsigned long DisplayTimer; 
static unsigned long DisplayDelay = 200;

LiquidCrystal lcd(12, 11, 9, 8, 7, 6); 


int buttonPin1 = 2;   
int buttonPin2 = 3;
int buttonPin3 = 4;
int buttonPin4 = 5;

int enterbutton = 10; 
int clearlockbutton = 13;

Servo myServo;

void setup() {

  myServo.attach(A1);

  int EEPROMCodeOK = true;
  for (Pos = 0; Pos <= (CodeLength); Pos++) {
    Str[Pos] =  EEPROM.read(Pos);
    if (!(strrchr("1123456789", Str[Pos]))) { 
      // not a valid code
      EEPROMCodeOK = false;
    }
  }
  Pos++;
  Str[Pos] =  EEPROM.read(Pos); 
  if (Str[CodeLength + 1] != 'E') EEPROMCodeOK = false; 
  if (EEPROMCodeOK) {
    Str[CodeLength + 2] = '\0';
    strncpy(CODE, Str, CodeLength + 1);
  }
  ClearCode();

  pinMode(buttonPin1, INPUT_PULLUP);
  pinMode(buttonPin2, INPUT_PULLUP);
  pinMode(buttonPin3, INPUT_PULLUP);
  pinMode(buttonPin4, INPUT_PULLUP);

  pinMode(enterbutton, INPUT_PULLUP);
  pinMode(clearlockbutton, INPUT_PULLUP);

  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  lcd.print("Hello.");
  delay(2000);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Password:");

  DisplayTimer = millis() + 200;
}


void loop() {

  Lock();

  Pos = constrain(Pos, 0, CodeLength);

  int buttonState1 = digitalRead(buttonPin1);  
  int buttonState2 = digitalRead(buttonPin2);
  int buttonState3 = digitalRead(buttonPin3);
  int buttonState4 = digitalRead(buttonPin4);

  int clButtonState = digitalRead(clearlockbutton);
  int enterButtonState = digitalRead(enterbutton);

  lcd.setCursor(9, 0);

  if (buttonState1 == LOW) {
    Str[Pos] = '1';
    Pos++;
    Str[Pos] = '\0';
    delay(250); 
    while (digitalRead(buttonPin1) == LOW); 

  }

  else if (buttonState2 == LOW) {
    Str[Pos] = '2';
    Pos++;
    Str[Pos] = '\0';
    delay(250); 
    while (digitalRead(buttonPin2) == LOW);

  }

  else if (buttonState3 == LOW) {
    Str[Pos] = '3';
    Pos++;
    Str[Pos] = '\0';
    delay(250); 
    while (digitalRead(buttonPin3) == LOW);
  }

  else if (buttonState4 == LOW) {
    Str[Pos] = '4';
    Pos++;
    Str[Pos] = '\0';
    delay(250); 
    while (digitalRead(buttonPin4) == LOW); 

  }
  else if (enterButtonState == LOW) {
    Str[Pos] = 'E';
    Pos++;
    Str[Pos] = '\0';
    delay(250);
    while (digitalRead(buttonPin1) == LOW); 
     if (strcmp (Str,CODE) == 0) {
      Unlocked = true;
      lcd.setCursor(0, 0);
      lcd.print(" Access Granted");
      delay(2000);
      lcd.clear();
      lcd.print("    Unlocked");
    } 
    else if (SaveTimer > millis() && (Pos + 1) == CodeLength) { 

      strcpy(CODE, Str);
      for (Pos = 0; Pos <= (CodeLength + 1); Pos++) {
        EEPROM.write(Pos, Str[Pos]);
      }
      lcd.setCursor(0, 0);
      lcd.print("Saving Code:");
      lcd.setCursor(0, 1);
      lcd.print(Str);

      Unlocked = true;
    }

    else { 

      lcd.clear();
      lcd.print(" Access Denied.");
      delay(2000);
      lcd.clear();
      lcd.print("Password:");

    }

    while (Unlocked) {
      Unlock();
      if (digitalRead(clearlockbutton) == LOW) {
        delay(200);
        lcd.clear();
        lcd.print("     Locked");
        delay(2000);
        lcd.clear();
        Unlocked = false;
        SaveTimer = millis() + 30000;
      }
    }

    ClearCode();


  }

  else if (clButtonState == LOW) {
    delay(500);

    while (clearlockbutton == LOW);
    if ((millis() - SaveTimer) > 4500) {

    }

    ClearCode();

  }

  if ( (long)( millis() - DisplayTimer ) >= 0) {
    DisplayTimer += DisplayDelay;
    lcd.setCursor(9, 0); 
    lcd.print(Str);
    lcd.print("     ");

  }
}

void ClearCode() {

  Pos = 0;
  Str[Pos] = '\0';
  lcd.setCursor(0, 0);
  lcd.print("Password:");
  lcd.setCursor(0, 1);
  lcd.print("          ");

}

void Unlock() {

  myServo.write(150);

}

void Lock() {

  myServo.write(50);

}


user60552: Please add a foto of the display. Most likely you have problem with a contrast. Schematic at the link you've provided is very strange: pin 3, which is responsible for the contrast, is tied directly to GND, which sets the display to the minimum contrast. You should use either a potentiometer, or a voltage divider for this pin.

62121: <p>I’ve been trying to make this project: <a href="https://create.arduino.cc/projecthub/chummer1010/electronic-safe-with-arduino-25d039" rel="nofollow noreferrer">https://create.arduino.cc/projecthub/chummer1010/electronic-safe-with-arduino-25d039</a></p>

<p>I’m confident that I’ve assembled everything correctly, but my LCD doesn’t display characters. Other projects seem to have fixed it by changing the potentiometer but I’m not using one. </p>

<p>Arduino code:</p>

<pre><code>/* 
Made by Marco Fusco
May 20, 2016
Contact me at: marcofusco111@gmail.com
*/


#include &lt;LiquidCrystal.h&gt;
#include &lt;EEPROM.h&gt;
#include &lt;Servo.h&gt;

int address = 0;
static unsigned long SaveTimer;
static unsigned long SaveDelay = (30 * 1000); 


char CODE[10] = "1234E"; 
char Str[10]; 
char CodeLength = 4;
int Pos = 0;
bool Unlocked;
static unsigned long DisplayTimer; 
static unsigned long DisplayDelay = 200;

LiquidCrystal lcd(12, 11, 9, 8, 7, 6); 


int buttonPin1 = 2;   
int buttonPin2 = 3;
int buttonPin3 = 4;
int buttonPin4 = 5;

int enterbutton = 10; 
int clearlockbutton = 13;

Servo myServo;

void setup() {

  myServo.attach(A1);

  int EEPROMCodeOK = true;
  for (Pos = 0; Pos &lt;= (CodeLength); Pos++) {
    Str[Pos] =  EEPROM.read(Pos);
    if (!(strrchr("1123456789", Str[Pos]))) { 
      // not a valid code
      EEPROMCodeOK = false;
    }
  }
  Pos++;
  Str[Pos] =  EEPROM.read(Pos); 
  if (Str[CodeLength + 1] != 'E') EEPROMCodeOK = false; 
  if (EEPROMCodeOK) {
    Str[CodeLength + 2] = '\0';
    strncpy(CODE, Str, CodeLength + 1);
  }
  ClearCode();

  pinMode(buttonPin1, INPUT_PULLUP);
  pinMode(buttonPin2, INPUT_PULLUP);
  pinMode(buttonPin3, INPUT_PULLUP);
  pinMode(buttonPin4, INPUT_PULLUP);

  pinMode(enterbutton, INPUT_PULLUP);
  pinMode(clearlockbutton, INPUT_PULLUP);

  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  lcd.print("Hello.");
  delay(2000);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Password:");

  DisplayTimer = millis() + 200;
}


void loop() {

  Lock();

  Pos = constrain(Pos, 0, CodeLength);

  int buttonState1 = digitalRead(buttonPin1);  
  int buttonState2 = digitalRead(buttonPin2);
  int buttonState3 = digitalRead(buttonPin3);
  int buttonState4 = digitalRead(buttonPin4);

  int clButtonState = digitalRead(clearlockbutton);
  int enterButtonState = digitalRead(enterbutton);

  lcd.setCursor(9, 0);

  if (buttonState1 == LOW) {
    Str[Pos] = '1';
    Pos++;
    Str[Pos] = '\0';
    delay(250); 
    while (digitalRead(buttonPin1) == LOW); 

  }

  else if (buttonState2 == LOW) {
    Str[Pos] = '2';
    Pos++;
    Str[Pos] = '\0';
    delay(250); 
    while (digitalRead(buttonPin2) == LOW);

  }

  else if (buttonState3 == LOW) {
    Str[Pos] = '3';
    Pos++;
    Str[Pos] = '\0';
    delay(250); 
    while (digitalRead(buttonPin3) == LOW);
  }

  else if (buttonState4 == LOW) {
    Str[Pos] = '4';
    Pos++;
    Str[Pos] = '\0';
    delay(250); 
    while (digitalRead(buttonPin4) == LOW); 

  }
  else if (enterButtonState == LOW) {
    Str[Pos] = 'E';
    Pos++;
    Str[Pos] = '\0';
    delay(250);
    while (digitalRead(buttonPin1) == LOW); 
     if (strcmp (Str,CODE) == 0) {
      Unlocked = true;
      lcd.setCursor(0, 0);
      lcd.print(" Access Granted");
      delay(2000);
      lcd.clear();
      lcd.print("    Unlocked");
    } 
    else if (SaveTimer &gt; millis() &amp;&amp; (Pos + 1) == CodeLength) { 

      strcpy(CODE, Str);
      for (Pos = 0; Pos &lt;= (CodeLength + 1); Pos++) {
        EEPROM.write(Pos, Str[Pos]);
      }
      lcd.setCursor(0, 0);
      lcd.print("Saving Code:");
      lcd.setCursor(0, 1);
      lcd.print(Str);

      Unlocked = true;
    }

    else { 

      lcd.clear();
      lcd.print(" Access Denied.");
      delay(2000);
      lcd.clear();
      lcd.print("Password:");

    }

    while (Unlocked) {
      Unlock();
      if (digitalRead(clearlockbutton) == LOW) {
        delay(200);
        lcd.clear();
        lcd.print("     Locked");
        delay(2000);
        lcd.clear();
        Unlocked = false;
        SaveTimer = millis() + 30000;
      }
    }

    ClearCode();


  }

  else if (clButtonState == LOW) {
    delay(500);

    while (clearlockbutton == LOW);
    if ((millis() - SaveTimer) &gt; 4500) {

    }

    ClearCode();

  }

  if ( (long)( millis() - DisplayTimer ) &gt;= 0) {
    DisplayTimer += DisplayDelay;
    lcd.setCursor(9, 0); 
    lcd.print(Str);
    lcd.print("     ");

  }
}

void ClearCode() {

  Pos = 0;
  Str[Pos] = '\0';
  lcd.setCursor(0, 0);
  lcd.print("Password:");
  lcd.setCursor(0, 1);
  lcd.print("          ");

}

void Unlock() {

  myServo.write(150);

}

void Lock() {

  myServo.write(50);

}
</code></pre>
 60552: <p>Please add a foto of the display. Most likely you have problem with a contrast. Schematic at the link you've provided is very strange: pin 3, which is responsible for the contrast, is tied directly to GND, which sets the display to the minimum contrast. You should use either a potentiometer, or a voltage divider for this pin.</p>
