Arduino + LCD Display as a Bicycle Speedometer

1/*
2  Arduino Speedometer
3  by Cesare Brizio | CC by-sa-nc
4  this   sketch is in the public domain
5
6  Version 1.0 - 26 february 2019
7  ------------------------------
8   The implementation is relatively rough: 
9  - wheel circumference has to be   hard-coded
10  - an attempt at debouncing has been made both at ohysical and software
11     level - to no avail. Will be revised soon.
12  A few more details here:
13   http://www.cesarebrizio.it/Arduino/Speedometer.html 
14  
15  Modified from   an original by John Boxall
16  Example 37.3 – Basic speedometer using millis();
17   http://tronixstuff.com/tutorials > chapter 37
18  John Boxall | CC by-sa-nc
19
20   Hardware – you will need a sensor. For example – a reed switch and magnet. 
21   Consider the reed switch to be a normally-open button, and connect as usual 
22   with a pull-down resistor.
23 
24  ==========================
25  The circuit   for LCD board
26  (HD4770 compatible display)
27  4-wire dialogue
28  ==========================
29   * LCD RS pin to digital pin 15
30 * LCD Enable pin to digital pin 14
31 * LCD   D4 pin to digital pin 5
32 * LCD D5 pin to digital pin 4
33 * LCD D6 pin to digital   pin 3
34 * LCD D7 pin to digital pin 2
35 * LCD R/W pin to ground
36 * LCD VSS   pin to ground
37 * LCD VCC pin to 5V
38 * 10K resistor:
39 * ends to +5V and   ground
40 * wiper to LCD VO pin (pin 3)
41
42*/
43
44// include the library   code:
45#include <LiquidCrystal.h>
46
47// initialize the library with the numbers   of the interface pins
48const int rs = 13, en = 12, d4 = 11, d5 = 10, d6 = 9, d7   = 8;
49LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
50 
51float start, finished;
52float   elapsed, time;
53float circMetric=2.093; // wheel circumference (in meters)
54float   circImperial; // using 1 kilometer = 0.621371192 miles
55float speedk, speedm;     // holds calculated speed vales in metric and imperial
56 
57void setup()
58{
59   // convert metric to imperial for MPH calculations
60  circImperial=circMetric*.62137;   
61
62  // the syntax with digitalPinToInterrupt should allow portability
63   //among different Arduino models - see https://www.arduino.cc/reference/en/language/functions/external-interrupts/attachinterrupt/
64   attachInterrupt(digitalPinToInterrupt(2), speedCalc, RISING); // interrupt called   when sensors sends digital 2 high (every wheel rotation)
65  //attachInterrupt(0,   speedCalc, RISING); // interrupt called when sensors sends digital 2 high (every   wheel rotation)
66
67  //start now (it will be reset by the interrupt after calculating   revolution time)
68  start=millis(); 
69
70  // set up the LCD's number of columns   and rows:
71  lcd.begin(16, 2);
72
73  // Print a transitory message to the LCD.
74   lcd.print("Ardu-Speedometer");
75  delay(2000); //just to allow you to read   the initialization message
76
77  // top serial dialogue speed improves precision
78   Serial.begin(115200);
79}
80 
81void speedCalc()
82{
83  //Function called   by the interrupt
84
85  if((millis()-start)>100) // 100 millisec debounce
86     {
87    //calculate elapsed
88    elapsed=millis()-start;
89
90    //reset   start
91    start=millis();
92  
93    //calculate speed in km/h
94    speedk=(3600*circMetric)/elapsed;   
95
96    //calculate speed in mph
97    speedm=(3600*circImperial)/elapsed;   
98    }
99}
100 
101void loop()
102{
103  // The loop will be interrupted by   the sensor each time the 
104  // magnet passes near the sensor, in other words   once per revolution
105
106  // Top line in the 16 char, 2 lines display - speed   data
107  lcd.setCursor(0,0);
108  lcd.print("                ");
109  lcd.setCursor(0,0);
110   lcd.print(int(speedk));
111  lcd.print(" km/h ");
112  lcd.print(int(speedm));
113   lcd.print(" MPH ");
114
115  //bottom line the 16 char, 2 lines display - time   data
116  lcd.setCursor(0,1);
117  lcd.print("                ");
118  lcd.setCursor(0,1);
119   lcd.print(int(elapsed));
120  lcd.print(" ms/rev      ");
121
122  // adjust   for personal preference to minimise flicker
123  //delay(250); 
124}

1/*
2  Arduino Speedometer
3  by Cesare Brizio | CC by-sa-nc
4  this  sketch is in the public domain
5
6  Version 1.0 - 26 february 2019
7  ------------------------------
8  The implementation is relatively rough: 
9  - wheel circumference has to be  hard-coded
10  - an attempt at debouncing has been made both at ohysical and software
11    level - to no avail. Will be revised soon.
12  A few more details here:
13  http://www.cesarebrizio.it/Arduino/Speedometer.html 
14  
15  Modified from  an original by John Boxall
16  Example 37.3 – Basic speedometer using millis();
17  http://tronixstuff.com/tutorials > chapter 37
18  John Boxall | CC by-sa-nc
19
20  Hardware – you will need a sensor. For example – a reed switch and magnet. 
21  Consider the reed switch to be a normally-open button, and connect as usual 
22  with a pull-down resistor.
23 
24  ==========================
25  The circuit  for LCD board
26  (HD4770 compatible display)
27  4-wire dialogue
28  ==========================
29  * LCD RS pin to digital pin 15
30 * LCD Enable pin to digital pin 14
31 * LCD  D4 pin to digital pin 5
32 * LCD D5 pin to digital pin 4
33 * LCD D6 pin to digital  pin 3
34 * LCD D7 pin to digital pin 2
35 * LCD R/W pin to ground
36 * LCD VSS  pin to ground
37 * LCD VCC pin to 5V
38 * 10K resistor:
39 * ends to +5V and  ground
40 * wiper to LCD VO pin (pin 3)
41
42*/
43
44// include the library  code:
45#include <LiquidCrystal.h>
46
47// initialize the library with the numbers  of the interface pins
48const int rs = 13, en = 12, d4 = 11, d5 = 10, d6 = 9, d7  = 8;
49LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
50 
51float start, finished;
52float  elapsed, time;
53float circMetric=2.093; // wheel circumference (in meters)
54float  circImperial; // using 1 kilometer = 0.621371192 miles
55float speedk, speedm;    // holds calculated speed vales in metric and imperial
56 
57void setup()
58{
59  // convert metric to imperial for MPH calculations
60  circImperial=circMetric*.62137;  
61
62  // the syntax with digitalPinToInterrupt should allow portability
63  //among different Arduino models - see https://www.arduino.cc/reference/en/language/functions/external-interrupts/attachinterrupt/
64  attachInterrupt(digitalPinToInterrupt(2), speedCalc, RISING); // interrupt called  when sensors sends digital 2 high (every wheel rotation)
65  //attachInterrupt(0,  speedCalc, RISING); // interrupt called when sensors sends digital 2 high (every  wheel rotation)
66
67  //start now (it will be reset by the interrupt after calculating  revolution time)
68  start=millis(); 
69
70  // set up the LCD's number of columns  and rows:
71  lcd.begin(16, 2);
72
73  // Print a transitory message to the LCD.
74  lcd.print("Ardu-Speedometer");
75  delay(2000); //just to allow you to read  the initialization message
76
77  // top serial dialogue speed improves precision
78  Serial.begin(115200);
79}
80 
81void speedCalc()
82{
83  //Function called  by the interrupt
84
85  if((millis()-start)>100) // 100 millisec debounce
86    {
87    //calculate elapsed
88    elapsed=millis()-start;
89
90    //reset  start
91    start=millis();
92  
93    //calculate speed in km/h
94    speedk=(3600*circMetric)/elapsed;  
95
96    //calculate speed in mph
97    speedm=(3600*circImperial)/elapsed;  
98    }
99}
100 
101void loop()
102{
103  // The loop will be interrupted by  the sensor each time the 
104  // magnet passes near the sensor, in other words  once per revolution
105
106  // Top line in the 16 char, 2 lines display - speed  data
107  lcd.setCursor(0,0);
108  lcd.print("                ");
109  lcd.setCursor(0,0);
110  lcd.print(int(speedk));
111  lcd.print(" km/h ");
112  lcd.print(int(speedm));
113  lcd.print(" MPH ");
114
115  //bottom line the 16 char, 2 lines display - time  data
116  lcd.setCursor(0,1);
117  lcd.print("                ");
118  lcd.setCursor(0,1);
119  lcd.print(int(elapsed));
120  lcd.print(" ms/rev      ");
121
122  // adjust  for personal preference to minimise flicker
123  //delay(250); 
124}