Lap Timer

I built this circuit to test the time taken for a line following buggy to complete one lap in a track that I created. Myself and my friend used this circuit to measure the best time taken.

The circuit consists of

• 2 push buttons to select which user is racing next
• LCD display to show the best time and the current time while the timer is running
• A power supply consisting of a 9V battery connected to two voltage dividers that step down the voltage to 5V and 3.3V.
• A sensor circuit fabricated by my friend which outputs a logic high when the sensor detects any object in front of it at a limited range.
  
  

To get started, I built the circuit with an Arduino Uno R3. After successfully making basic connections to the arduino and debugging my code I decided the make the circuit with a MSP430 to make it smaller and more portable.

The MSP430 operates at 3.3V but the LCD display needs more than that to record a logic high. To overcome this problem AND gates were used to increase the output to the LCD display connections increase to 4.5V.

If you want to create a similar circuit with an arduino all you have to do is the following.

• Read and be familiarised with the “Liquid Crystal” library that comes with the Arduino software.
• Make connections to the LCD display as shown in the library.
• Fix two switches and wire it to the arduino.
• Get a basic IR emitter and a receiver (It is easier to get a TCRT5000). Then wire the receiver same as the switches. Instead of connecting it straight to the arduino, connect it to a comparator and use a voltage regulator to control the output signal.
• If necessary use a Voltage regulator to drop the voltage from your source to 5V.

You can write your own program. but here is a copy of my program.

#include <LiquidCrystal.h> LiquidCrystal lcd(12, 11, 5, 4, 3, 2); int mode = 0; int racer1 = 500; int racer2 = 500; int i, x, y, z, time; int m = 0; void setup() { lcd.begin(16, 2); pinMode(9, INPUT); pinMode(10, INPUT); pinMode(8, INPUT); } void loop() { while (mode == 0){ x = digitalRead(9); y = digitalRead(10); if (x == 1){ mode = 1; } else if (y == 1){ mode = 2; } lcd.setCursor(0, 0); lcd.print("Racer 1"); lcd.setCursor(10, 0); lcd.print(john); lcd.setCursor(0, 1); lcd.print("Racer 2"); lcd.setCursor(10, 1); lcd.print(nigel); } while (mode == 1){ time = 0; m = 0; lcd.clear(); lcd.setCursor(0, 0); lcd.print("Racer 1"); lcd.setCursor(0, 1); while (m == 0){ z = digitalRead(8); if (z == 1){ m = 1; } } while (m == 1){ for(i = 0; i<20; i++){ delay(50); z = digitalRead(8); if (time > 3) if (z == 1){ m = 0; } } time++; lcd.setCursor(0, 1); lcd.print(time); } if (time < racer1){ racer1 = time; } mode = 0; lcd.clear(); } while (mode == 2){ time = 0; m = 0; lcd.clear(); lcd.setCursor(0, 0); lcd.print("Racer 2"); lcd.setCursor(0, 1); while (m == 0){ z = digitalRead(8); if (z == 1){ m = 1; } } while (m == 1){ for(i = 0; i<20; i++){ delay(50); z = digitalRead(8); if (time > 3) if (z == 1){ m = 0; } } time++; lcd.setCursor(0, 1); lcd.print(time); } if (time < racer2){ racer2= time; } mode = 0; lcd.clear(); } }  

 Here is a demonstration