Introduction

In this article, I have explained about creating a simple calculator with Arduino Mega 2560. It can be used to calculate for Addition, Multiplication, Division, and Subtraction. The result will be displayed in the LCD.
Parts Of Lists
  • Arduino Mega 2560
  • LEDs
  • Push Button
  • Potentiometer
  • LCD Display
  • Bread Board
  • Hookup Wires
Potentiometer
  • It can have three terminals.
  • It can have sliding or rotating contact that forms an adjustable voltage divider.
  • It acts as a variable resistor (or) rheostat.
Figure 1: Potentiometer
LCD Display
  • LCD is Liquid Crystal Display (LCD).
  • It can have flat-panel or electronic display
  • It is used in hospital, showrooms, buses, railway stations, airports, etc.
Figure 2: LCD Display
Push Button
  • The push-button connects the two points.
  • The first pin in the push button is connected to 5Vc.
  • The second pin in the push button is connected to gnd.
Figure 3: Push Button
Connection
Step 1: Connection from Arduino Mega 2560 to LCD Display.
  • Fix the LCD in the 16 to 2 in the bread board.
  • The 16 pin to the Gnd
  • The 15 pin to the Vcc
  • The 14 pin to the Digital pin 12
  • The 13 pin to the Digital pin 11
  • The 12 pin to the Digital pin 05
  • The 11 pin to the Digital pin 04
  • The 01 pin to the Gnd.
  • The 02 pin to the Vcc.
  • The 03 pin to the potentiometer.
  • The 04 pin to the Digital pin 03.
  • The 05 pin to the Gnd.
  • The 06 pin to the Digital pin 02.
Figure 4: LCD Display connection
Step 2: Connection from Push Button to ArduinoMega2560
Push-button 1:
  • The first pin in the push button is connected to 5Vc and 12 of board
  • The second pin in the push button is connected to gnd.
Push-button 2:
  • The first pin in the push button is connected to 5Vc and 13 of board
  • The second pin in the push button is connected to gnd.
Push-button 3:
  • The first pin in the push button is connected to 5Vc and 14 of board
  • The second pin in the push button is connected to gnd.
Push-button 4:
  • The first pin in the push button is connected to 5Vc and 15 of board
  • The second pin in the push button is connected to gnd.
Push-button 5:
  • The first pin in the push button is connected to 5Vc and 16 of board
  • The second pin in the push button is connected to gnd.
Push-button 6:
  • The first pin in the push button is connected to 5Vc and 17 of board
  • The second pin in the push button is connected to gnd.
Push-button 7:
  • The first pin in the push button is connected to 5Vc and 18 of board
  • The second pin in the push button is connected to gnd.
Push-button 8:
  • The first pin in the push button is connected to 5Vc and 19 of board
  • The second pin in the push button is connected to gnd.
Push-button 9:
  • The first pin in the push button is connected to 5Vc and 20 of board
  • The second pin in the push button is connected to gnd.
Push-button 10:
  • The first pin in the push button is connected to 5Vc and 21 of board
  • The second pin in the push button is connected to gnd.
Push-button 11:
  • The first pin in the push button is connected to 5Vc and 22 of board
  • The second pin in the push button is connected to gnd.
Push-button 12:
  • The first pin in the push button is connected to 5Vc and 23 of board
  • The second pin in the push button is connected to gnd.
Programming:
  1. // include the library code:
  2. #include <LiquidCrystal.h>
  4. #define key0 12
  5. #define key1 13
  6. #define key2 14
  7. #define key3 15
  8. #define key4 16
  9. #define key5 17
  10. #define key6 18
  11. #define key7 19
  12. #define key8 20
  13. #define key9 21
  14. #define DEL 22
  15. #define ENTER 23
  16. #define MAXVALUE 99999
  18. // initialize the library with the numbers of the interface pins
  19. LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
  21. long number_1 = 0;
  22. long number_2 = 0;
  23. int control = 0;
  24. boolean error = false;
  25. long result = 0;
  26. float result_div = 0.0;
  28. void insertNumb () {
  29. for (int i = 0; i <= 9; i++) {
  30. //whithout this delay, the selection button pressed could become the first digit
  31. delay (200);
  32. lcd.clear();
  33. lcd.setCursor(0, 0);
  34. lcd.print("FIRST NUMBER");
  35. control = readKey ();
  36. //statement needed to catch the first digit
  37. if ( i == 0 ) {
  38. //statement needed to check if the pressed button is the special key OK
  39. //if yes "i" becomes 5 and the algorithm goes to the next for loop
  40. if ( control == 11 ) {
  41. i = 5;
  42. }
  43. //statement needed to check if the pressed button is the special key DEL
  44. //if yes "i" becomes 10 and the algorithm goes from both for loops
  45. //resetting the calculator
  46. else if ( control == 10) {
  47. i = 10;
  48. error = true;
  49. lcd.clear();
  50. lcd.setCursor(0, 0);
  51. lcd.print("CANCELLED!");
  52. delay(2000);
  53. }
  54. else {
  55. //stores the most significant digit
  56. number_1 = control;
  57. lcd.clear();
  58. lcd.setCursor(0, 1);
  59. lcd.print(control);
  60. delay(500);
  61. }
  62. }
  63. //statement needed to catch the remaining four digits
  64. //the following conditional statements have the same purpose of the ones described above
  65. else {
  66. if ( control == 11 ) {
  67. i = 5;
  68. }
  69. else if ( control == 10) {
  70. i = 10;
  71. error = true;
  72. lcd.clear();
  73. lcd.setCursor(0, 0);
  74. lcd.print("CANCELLED!");
  75. delay(2000);
  76. }
  77. else {
  78. number_1 = (number_1 * 10) + control;
  79. //check if number_1 is negative or is greater than MAXVALUE printing an error if yes
  80. if ((number_1 < 0) || (number_1 > MAXVALUE)) {
  81. error = true;
  82. i = 10;
  83. lcd.clear();
  84. lcd.setCursor(0, 0);
  85. lcd.print("ERROR!");
  86. lcd.setCursor(0, 1);
  87. lcd.print("MAX VALUE " + (String)MAXVALUE);
  88. delay(2000);
  89. }
  90. else {
  91. lcd.clear();
  92. lcd.setCursor(0, 1);
  93. lcd.print(control);
  94. lcd.setCursor(0, 0);
  95. lcd.print(number_1);
  96. delay(500);
  97. }
  98. }
  99. }
  100. if (i >= 4 && i <= 9) {
  101. //the following for loop catches the digits of the second number
  102. //and basically does the same thing as the previous one
  103. for (int j = 0; j <= 4; j++) {
  104. delay (200);
  105. lcd.clear();
  106. lcd.setCursor(0, 0);
  107. lcd.print("SECOND NUMBER");
  108. control = readKey ();
  109. i++;
  110. if ( j == 0 ) {
  111. if ( control == 11 ) {
  112. i = 10;
  113. j = 5;
  114. }
  115. else if ( control == 10 ) {
  116. error = true;
  117. j = 5;
  118. i = 10;
  119. lcd.clear();
  120. lcd.setCursor(0, 0);
  121. lcd.print("CANCELLED!");
  122. delay(2000);
  123. }
  124. else {
  125. number_2 = control;
  126. lcd.clear();
  127. lcd.setCursor(0, 1);
  128. lcd.print(control);
  129. delay(500);
  130. }
  131. }
  132. else {
  133. if ( control == 11 ) {
  134. j = 5;
  135. i = 10;
  136. }
  137. else if ( control == 10 ) {
  138. error = true;
  139. j = 5;
  140. i = 10;
  141. lcd.clear();
  142. lcd.setCursor(0, 0);
  143. lcd.print("CANCELLED!");
  144. delay(2000);
  145. }
  146. else {
  147. number_2 = (number_2 * 10) + control;
  148. //check if number_2 is negative or is greater than MAXVALUE printing an error if yes
  149. if ((number_2 < 0) || (number_2 > MAXVALUE)) {
  150. error = true;
  151. j = 5;
  152. i = 10;
  153. lcd.clear();
  154. lcd.setCursor(0, 0);
  155. lcd.print("ERROR!");
  156. lcd.setCursor(0, 1);
  157. lcd.print("MAX VALUE " + (String)MAXVALUE);
  158. delay(2000);
  159. }
  160. else {
  161. lcd.clear();
  162. lcd.setCursor(0, 1);
  163. lcd.print(control);
  164. lcd.setCursor(0, 0);
  165. lcd.print(number_2);
  166. delay(500);
  167. }
  168. }
  169. }
  170. }
  171. }
  172. }
  174. }
  176. void wait () {
  177. while (digitalRead(key0) == LOW &&
  178. digitalRead(key1) == LOW &&
  179. digitalRead(key2) == LOW &&
  180. digitalRead(key3) == LOW &&
  181. digitalRead(key4) == LOW &&
  182. digitalRead(key5) == LOW &&
  183. digitalRead(key6) == LOW &&
  184. digitalRead(key7) == LOW &&
  185. digitalRead(key8) == LOW &&
  186. digitalRead(key9) == LOW &&
  187. digitalRead(DEL) == LOW &&
  188. digitalRead(ENTER) == LOW
  189. );
  190. }
  192. void setup() {
  193. //initializes push-buttons
  194. pinMode(key0, INPUT);
  195. pinMode(key1, INPUT);
  196. pinMode(key2, INPUT);
  197. pinMode(key3, INPUT);
  198. pinMode(key4, INPUT);
  199. pinMode(key5, INPUT);
  200. pinMode(key6, INPUT);
  201. pinMode(key7, INPUT);
  202. pinMode(key8, INPUT);
  203. pinMode(key9, INPUT);
  204. pinMode(DEL, INPUT);
  205. pinMode(ENTER, INPUT);
  206. // set up the LCD's number of columns and rows:
  207. lcd.begin(16, 2);
  208. }
  210. int readKey () {
  211. wait();
  212. int operand = 0;
  213. if (digitalRead(key0) == HIGH) {
  214. operand = 0;
  215. }
  216. else if (digitalRead(key1) == HIGH) {
  217. operand = 1;
  218. }
  219. else if (digitalRead(key2) == HIGH) {
  220. operand = 2;
  221. }
  222. else if (digitalRead(key3) == HIGH) {
  223. operand = 3;
  224. }
  225. else if (digitalRead(key4) == HIGH) {
  226. operand = 4;
  227. }
  228. else if (digitalRead(key5) == HIGH) {
  229. operand = 5;
  230. }
  231. else if (digitalRead(key6) == HIGH) {
  232. operand = 6;
  233. }
  234. else if (digitalRead(key7) == HIGH) {
  235. operand = 7;
  236. }
  237. else if (digitalRead(key8) == HIGH) {
  238. operand = 8;
  239. }
  240. else if (digitalRead(key9) == HIGH) {
  241. operand = 9;
  242. }
  243. else if (digitalRead(DEL) == HIGH) {
  244. operand = 10;
  245. }
  246. else if (digitalRead(ENTER) == HIGH) {
  247. operand = 11;
  248. }
  249. delay(100);
  250. return operand;
  251. }
  253. //SUM function
  254. long sum (long number_1, long number_2) {
  255. return number_1 + number_2;
  256. }
  258. //SUBtraction function
  259. long subtraction (long number_1, long number_2) {
  260. return number_1 - number_2;
  261. }
  263. //MULtiplication function
  264. long multiplication (long number_1, long number_2) {
  265. return number_1 * number_2;
  266. }
  268. //DIVsion FUNCTION
  269. float division (long number_1, long number_2) {
  270. return (float)number_1 / (float)number_2;
  271. }
  273. void loop() {
  274. number_1 = 0;
  275. number_2 = 0;
  276. delay (200);
  277. //asks which calculation you want to do
  278. lcd.clear();
  279. lcd.setCursor(0, 0);
  280. lcd.print("SUM,SUB,MUL,DIV");
  281. lcd.setCursor(0, 1);
  282. lcd.print("0 ,1 ,2 ,3 ");
  283. //waits into the following loop till the user press a key
  284. wait();
  285. //"operation" is the variable needed to control the flow of the sketch
  286. int operation = readKey();
  287. //SUM
  288. if (operation == 0) {
  289. insertNumb();
  290. if (error == true) {
  291. lcd.clear();
  292. lcd.setCursor(0, 0);
  293. lcd.print("DEL TO CONTINUE");
  294. }
  295. else {
  296. lcd.clear();
  297. lcd.setCursor(0, 0);
  298. lcd.print("DEL TO CONTINUE");
  299. lcd.setCursor(0, 1);
  300. lcd.print("SUM = ");
  301. lcd.setCursor(7, 1);
  302. result = sum(number_1, number_2);
  303. if (result < MAXVALUE) {
  304. lcd.print(result);
  305. } else {
  306. lcd.clear();
  307. lcd.setCursor(0, 0);
  308. lcd.print("ERROR!");
  309. lcd.setCursor(0, 1);
  310. lcd.print("MAX VALUE " + (String)MAXVALUE);
  311. delay(4000);
  312. lcd.clear();
  313. lcd.setCursor(0, 0);
  314. lcd.print("DEL TO CONTINUE");
  315. }
  316. }
  317. while (readKey() != 10);
  318. }
  319. else if (operation == 1) {
  320. insertNumb();
  321. if (error == true) {
  322. lcd.clear();
  323. lcd.setCursor(0, 0);
  324. lcd.print("DEL TO CONTINUE");
  325. } else {
  326. lcd.clear();
  327. lcd.setCursor(0, 0);
  328. lcd.print("DEL TO CONTINUE");
  329. lcd.setCursor(0, 1);
  330. lcd.print("SUB = ");
  331. lcd.setCursor(7, 1);
  332. result = subtraction(number_1, number_2);
  333. if (result < MAXVALUE) {
  334. lcd.print(result);
  335. } else {
  336. lcd.clear();
  337. lcd.setCursor(0, 0);
  338. lcd.print("ERROR!");
  339. lcd.setCursor(0, 1);
  340. lcd.print("MAX VALUE " + (String)MAXVALUE);
  341. delay(4000);
  342. lcd.clear();
  343. lcd.setCursor(0, 0);
  344. lcd.print("DEL TO CONTINUE");
  345. }
  346. }
  347. while (readKey() != 10);
  348. }
  349. else if (operation == 2) {
  350. insertNumb();
  351. if (error == true) {
  352. lcd.clear();
  353. lcd.setCursor(0, 0);
  354. lcd.print("DEL TO CONTINUE");
  355. } else {
  356. lcd.clear();
  357. lcd.setCursor(0, 0);
  358. lcd.print("DEL TO CONTINUE");
  359. lcd.setCursor(0, 1);
  360. lcd.print("MUL = ");
  361. lcd.setCursor(7, 1);
  362. result = multiplication(number_1, number_2);
  363. if (result < MAXVALUE) {
  364. lcd.print(result);
  365. } else {
  366. lcd.clear();
  367. lcd.setCursor(0, 0);
  368. lcd.print("ERROR!");
  369. lcd.setCursor(0, 1);
  370. lcd.print("MAX VALUE " + (String)MAXVALUE);
  371. delay(4000);
  372. lcd.clear();
  373. lcd.setCursor(0, 0);
  374. lcd.print("DEL TO CONTINUE");
  375. }
  376. }
  377. while (readKey() != 10);
  378. }
  379. else if (operation == 3) {
  380. insertNumb();
  381. if (error == true) {
  382. lcd.clear();
  383. lcd.setCursor(0, 0);
  384. lcd.print("DEL TO CONTINUE");
  385. } else {
  386. lcd.clear();
  387. lcd.setCursor(0, 0);
  388. lcd.print("DEL TO CONTINUE");
  389. lcd.setCursor(0, 1);
  390. lcd.print("DIV = ");
  391. lcd.setCursor(7, 1);
  392. result_div = division(number_1, number_2);
  393. if (result < MAXVALUE) {
  394. lcd.print(result_div, 7);
  395. } else {
  396. lcd.clear();
  397. lcd.setCursor(0, 0);
  398. lcd.print("ERROR!");
  399. lcd.setCursor(0, 1);
  400. lcd.print("MAX VALUE " + (String)MAXVALUE);
  401. delay(4000);
  402. lcd.clear();
  403. lcd.setCursor(0, 0);
  404. lcd.print("DEL TO CONTINUE");
  405. }
  406. }
  407. while (readKey() != 10);
  408. } else {
  409. lcd.clear();
  410. lcd.setCursor(0, 0);
  411. lcd.print("ERROR!");
  412. lcd.setCursor(0, 1);
  413. lcd.print("PRESS 0,1,2 or 3");
  414. delay(2000);
  415. }
  416. int control = 0;
  418. }
Explanation
  • This calculator can be used to calculate the for loop() function. It can be used to display one by one condition i.e addition/ subtraction/ multiplexing/ division.
  • The result can be displayed in the LCD display screen. If we made any mistake, press del to continue.
Output
Figure 5: Output