I will show you how to build a bike speedometer. It shows your speed,
the average speed,the temperature, the trip time and the total distance. You can change it using the button. Additionally, the speed is shown on a tachometer. I built it because I like building new things, I have not found anything like this on the internet so I want to show you how to build a good speedometer as the one on my bike is not as cool as I want :) . So let's get started.

Step 1: Parts:

This is a list of parts that you will need. They costed me about $ 40:

Arduino
Bike with reed switch
LCD display 16x2
Servo
Breadboard
Thermometer DS18B20
Resistor 1.2k Ω , 4.7k Ω
Switch
Button
Potentiometer 10 kΩ
9V battery
Cables
Box
Tools (drill, soldering, knife, tape)

Step 2: Connection

I added a picture from Fritzing and verbal description of how to connect it. In the picture all red wires are connected to 5V, all blue cables are connected to GND.

LCD display:

VSS --> GND Arduino

VDP --> 5V Arduino

VO --> output potentiometer (potentiometer VCC -> 5V Arduino, potentiometer GND -> Arduino GND).

RS --> pin 12 Arduino

RW --> GND Arduino

E --> pin 11 Arduino

D4 --> pin 5 Arduino

D5 --> pin 4 Arduino

D6 --> pin 3 Arduino

D7 --> pin 2 Arduino

A --> 5V Arduino

K --> GND Arduino

Servo:

VCC --> 5V Arduino

mass --> GND Arduino

Data --> pin 6 Arduino

Thermometer:

VCC --> 5V Arduino

mass --> GND Arduino

Data --> pin 1 Arduino

data and power is connected via a 4.7 kΩresistor

Sensor on wheel:

one end -> 5V Arduino

second end -> A0 Arduino and resistor 1,2 kΩ

The other end of the resistor to ground in the Arduino

Button:

one end --> 5V Arduino

second end --> A1 Arduino

Step 3: Upload Code:

Below I added the code in comments there is an explanation.

links to the download libraries:

http://www.pjrc.com/teensy/arduino_libraries/OneWire.zip

https://github.com/milesburton/Arduino-Temperature-Control-Library

If you have a different wheel diameter you have to change it. You can calculate it with this formula:

circuit = π*d*2,54 (d=diameter of your wheel, I multiplied it by 2.54 to get the result in meters).

/*
##################################################


Copyright by Nikodem Bartnik june 2014


##################################################
*/




//librarys
#include  < Servo.h>
#include <LiquidCrystal.h>
#include <OneWire.h>
#include <DallasTemperature.h>


#define ONE_WIRE_BUS 1
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);


//LCD display pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
//servo name
Servo myservo;
//definition of variables
 long previous, triptime, time, impulses;
 float speedometer, dist, aspeed;
 int servo;
 int screen=1;
 //If you have other circuit of wheel you need change it
 float circuit=2.0;
 double temperature;
 
 
 void setup() {


 lcd.begin(16, 2);</p><p>
  pinMode(A0, INPUT);
  pinMode(A1, INPUT);
  
  //servo definition and setting the tachometer to 0
  myservo.attach(6); 
  myservo.write(180);
  lcd.print("Bike tachometer");
  delay(1000);
  lcd.setCursor(5, 1);
  lcd.print("V 1.0");
  delay(4000);
  lcd.clear();
  delay(500);
  lcd.setCursor(0, 0);
  lcd.print("Dist:");
 } 




 void loop() {
   //if wheel turns
   if(analogRead(A0)>=300){
      //number of turns++
      impulses++;
      //count turn time
    time=(millis()-previous);
    //count speed
    speedometer=(circuit / time)*3600.0;
  previous=millis();
    Tachometer();
  delay(100);
}

  Lcd(); 
   }
   
   //display speed on tachometer
   void Tachometer(){
     //map speed 0-180 to servo
  speedometer=int(speedometer);
  servo = map(speedometer, 0, 72, 180, 0);
  //setup servo
  myservo.write(servo);
   }
  
  
  
    void Lcd(){
       //when button is clicked
      if(analogRead(A1)>=1010){
        lcd.clear();
      screen++;
      if(screen==5){
          screen=1;
        }
      }
   
        if(screen==1){
        //displays speed
        lcd.setCursor(0, 1);
        lcd.print("Speed:");
        lcd.setCursor(7, 1);
        lcd.print(speedometer);
        lcd.print("km/h");
        }
        
        if(screen==2){
          
        //displays themperature
        temperature=sensors.getTempCByIndex(0);
        sensors.requestTemperatures(); 
        lcd.setCursor(0, 1);
        lcd.print("Temp:");
        lcd.setCursor(7, 1);
        lcd.print(temperature);
        lcd.print(" C");
        }
        
        if(screen==3){
          //displays averagr speed
        aspeed=dist/(millis()/1000.0)*3600.0;
        lcd.setCursor(0, 1);
        lcd.print("A.speed:");
        lcd.setCursor(8, 1);
        lcd.print(aspeed);
        lcd.print("km/h");
        }
        
        if(screen== 4){
          //diplays trip time
        triptime=millis()/60000;
        
        lcd.setCursor(0, 1);
        lcd.print("Time:");
        lcd.setCursor(7, 1);
        lcd.print(triptime);
    
        
        }
        
       
        lcd.setCursor(0, 0);
        lcd.print("Dist:");
        //calculation of the distance
       dist=impulses*circuit/1000.00;
       //dislays distance
       lcd.setCursor(6,0);
       lcd.print(dist);
       lcd.print("km");
      }

bike_tachometer.ino
Download

Step 4: Pack

As a cover I used a plastic box I bought for $ 1. I cut holes using a knife and a drill. Servo and LCD display I glued with a tape, tip I made with carton and painted it with paint. I did shield in Corel Draw X5 and I printed it, I added a PNG image, and Corel Draw file (if you want, you can edit it). I clipped the box to steering wheel on my bike and I soldered cables to the reed switch.