iamJohnnySam: Project Portfolio: April 2013

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

Electronic Projects

Tuesday, 2 April 2013

Lap Timer