Fun Projects: Time Precision Challenge

What You Will Learn

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Circuit Connections

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This map shows you the physical map for building the project. It shows exactly where to plug in every wire for the buttons, LEDs, and screen so that the software instructions can correctly control all the hardware pieces.

Component	ESP32 Dev Module	The Function
I2C LCD SDA/SCL	SDA/SCL	The screen shows instructions and the final verdict
TM1650	SDA/SCL	This 4 digit display shows the time running down to 2 decimal places
Push Button	IO14	Press this button to start and stop the timer
Buzzer	IO27	Plays the countdown beep and celebration/fail tones
NEOPIXEL (RGB)	IO4	Lights up blue when the timer starts and flashes the result color

Code Lab

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This section holds the instructions for the ESP32. It’s the “brain” that tells the board exactly what to do, like when to flash a green light, what sound to play, and how to choose a random card. You copy and upload this code so your project can actually work.

Step 1: Install Library

For example:

Step 2: Full Code

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Adafruit_NeoPixel.h>
#include <TM1650.h>
#include <Bounce2.h>

#define BUTTON_PIN 14
#define BUZZER_PIN 27
#define CLK 22
#define DIO 21
#define LED_PIN 4
#define NUM_LEDS 6

LiquidCrystal_I2C lcd(0x27, 16, 2);
TM1650 DigitalTube(CLK, DIO);
Adafruit_NeoPixel strip(NUM_LEDS, LED_PIN, NEO_GRB + NEO_KHZ800);
Bounce debouncer = Bounce();

enum GameState { WAIT_START, COUNTDOWN, TIMING, RESULT };
GameState state = WAIT_START;

unsigned long startMillis;
float currentTime;
bool resultShown = false;

void setup() {
  Serial.begin(115200);

  pinMode(BUTTON_PIN, INPUT_PULLUP);
  pinMode(BUZZER_PIN, OUTPUT);

  debouncer.attach(BUTTON_PIN);
  debouncer.interval(25);

  lcd.init();
  lcd.backlight();

  TM1650 DigitalTube(CLK, DIO);
  for (char i = 0; i < 4; i++) {
    DigitalTube.clearBit(i);
  }

  strip.begin();
  strip.show();

  lcd.setCursor(0, 0);
  lcd.print("Reflex Tester");
  lcd.setCursor(0, 1);
  lcd.print("Press to Start");
}

void loop() {
  debouncer.update();

  switch (state) {
    case WAIT_START:
      if (debouncer.fell()) {
        lcd.clear();
        lcd.print("Get Ready...");
        state = COUNTDOWN;
        delay(1000);
      }
      break;

    case COUNTDOWN:
      for (int i = 3; i > 0; i--) {
        lcd.clear();
        lcd.print("Starting in ");
        lcd.print(i);
        tone(BUZZER_PIN, 1000, 200);
        delay(1000);
      }
      lcd.clear();
      lcd.print("Go!");
      strip.fill(strip.Color(0, 0, 255)); // Blue
      strip.show();

      startMillis = millis();
      resultShown = false;
      state = TIMING;
      break;

    case TIMING:
      currentTime = (millis() - startMillis) / 1000.0;

      if (currentTime <= 10.00) {
        DigitalTube.displayFloatNum((int)(currentTime * 100));
      } else {
        showResult(false);
        state = RESULT;
        break;
      }

      if (debouncer.fell()) {
        if (abs(currentTime - 5.00) <= 0.05) {
          showResult(true);
        } else {
          showResult(false);
        }
        state = RESULT;
      }
      break;

    case RESULT:
      if (debouncer.fell()) {
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Press to Start");
        for (char i = 0; i < 4; i++) {
          DigitalTube.clearBit(i);
        }
        strip.clear();
        strip.show();
        state = WAIT_START;
      }
      break;
  }
}

void showResult(bool success) {
  lcd.clear();
  resultShown = true;

  if (success) {
    lcd.print("Success!");
    tone(BUZZER_PIN, 2000, 300);
    ledPulse(strip.Color(0, 255, 0)); // Green
  } else {
    lcd.print("Too Slow/Fast");
    tone(BUZZER_PIN, 400, 500);
    ledFlash(strip.Color(255, 0, 0)); // Red
  }

  lcd.setCursor(0, 1);
  lcd.print("Time: ");
  lcd.print(currentTime, 2);
}

void ledPulse(uint32_t color) {
  for (int i = 0; i < NUM_LEDS; i++) {
    strip.setPixelColor(i, color);
  }
  strip.show();
  delay(600);
  strip.clear();
  strip.show();
}

void ledFlash(uint32_t color) {
  for (int i = 0; i < 3; i++) {
    strip.fill(color);
    strip.show();
    delay(200);
    strip.clear();
    strip.show();
    delay(200);
  }
}

How to Play

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The reflex Timer is a precise three-step process:

Condition	LCD Message	NeoPixel Feedback	Sound
SUCCESS! (Within ±0.05s of 5.00)	Success! / Time: 5.00	Flashes GREEN	A sharp, happy tone
FAILURE! (Too Fast, Too Slow, or Timeout)	Too Slow/Fast / Time: X.XX	Flashes RED	A low, sad failure tone
Timeout! (Takes longer than 10.00s)	Too Slow/Fast / Time: 10.00	Flashes RED	A low, sad failure tone Export to Sheets

Problem	What is Happening?	Simple Solution to Try
Button is erratic or double-clicks.	This is a wiring issue, but the Bounce2 library usually fixes it.	Check Wiring: Ensure the button is securely wired from GPIO14
LCD is blank / TM1650 is dark.	I2C communication or power is failing.	Check I2C Share: Ensure BOTH devices (LCD and TM1650) are correctly wired to GPIO21/22.
The 7-Segment Display (TM1650) is showing garbage.	The clock and data pins might be swapped.	Check Wiring: Double-check that CLK goes to SCK and DIO goes to SDA.
The NeoPixel strip won’t light up (GPIO4).	Power or Data pin connection is missing.	Check Data: Make sure Data In (DIN) is connected securely to GPIO4.
The buzzer is silent during the countdown.	The speaker is not connected correctly.	Check Wiring: Make sure the buzzer is correctly wired to GPIO27.