/ Freq_Meter

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Ohmmeter_Code.cpp@2:6077294f7007, 2020-04-01 (annotated)

Committer:
thomasosullivan
Date:
Wed Apr 01 19:45:59 2020 +0000
Revision:
2:6077294f7007
Parent:
1:5aacfef29ca8
Child:
3:b6e887e4ac75
Final with comments;

Who changed what in which revision?

UserRevisionLine numberNew contents of line
decland17 0:7f4ed364f7ea 1 /*
thomasosullivan 2:6077294f7007 2 the code is set up to auto range for different known resistance value
thomasosullivan 2:6077294f7007 3 it will base the case statement on its original Restimate value
thomasosullivan 2:6077294f7007 4 the voltage drop across the transistor is different for each case
thomasosullivan 2:6077294f7007 5 this value was found using simulations from LTspice
thomasosullivan 2:6077294f7007 6 a value for Runkown will be printed on the screen and this will be in a
thomasosullivan 2:6077294f7007 7 contunious loop from the switch
decland17 0:7f4ed364f7ea 8 */
decland17 0:7f4ed364f7ea 9 //Case x:
decland17 0:7f4ed364f7ea 10
decland17 0:7f4ed364f7ea 11 lcd.locate(0,0);
decland17 0:7f4ed364f7ea 12 lcd.printf("Resistance: "); //display on top line
decland17 0:7f4ed364f7ea 13
decland17 0:7f4ed364f7ea 14 DigitalOut 100ohm(D6) = 0; //Transistor connected to 100ohm resistor set to short circuit
decland17 0:7f4ed364f7ea 15 DigitalOut 1kohm(D7) = 1; //All others set to open circuit
decland17 0:7f4ed364f7ea 16 DigitalOut 10kohm(D8) = 1;
decland17 0:7f4ed364f7ea 17 DigitalOut 100kohm(D9) = 1;
decland17 0:7f4ed364f7ea 18 DigitalOut 1Mohm(D10) = 1;
decland17 0:7f4ed364f7ea 19 DigitalOut 10Mohm(D11) = 1;
decland17 0:7f4ed364f7ea 20
decland17 0:7f4ed364f7ea 21 AnalogIn vo(A0);
decland17 0:7f4ed364f7ea 22
thomasosullivan 2:6077294f7007 23 double vout = (3.3 * vo)/ 4095; //converts analog read from bits to voltage
decland17 0:7f4ed364f7ea 24
decland17 0:7f4ed364f7ea 25 double rest;
decland17 0:7f4ed364f7ea 26
decland17 0:7f4ed364f7ea 27 double vt;
decland17 0:7f4ed364f7ea 28
thomasosullivan 2:6077294f7007 29 rest = (vout * 100) / (3.3 - vout); //rest is an estimate as it does not account for the voltage drop in transistor
thomasosullivan 2:6077294f7007 30 //this essentially decides what pin we will use for final value
decland17 0:7f4ed364f7ea 31 switch (rest)
decland17 0:7f4ed364f7ea 32 {
decland17 0:7f4ed364f7ea 33 case 550:
thomasosullivan 2:6077294f7007 34 vt = 0.0647875; // vt is based off ltspice values from simulations
decland17 0:7f4ed364f7ea 35 runknown = (vout * 100) / (3.3 - vt - vout);
decland17 0:7f4ed364f7ea 36 if (runknown < 10){
thomasosullivan 2:6077294f7007 37 lcd.printf("Out of Range"); //this will be out of the range of our design parameters
decland17 0:7f4ed364f7ea 38 }
decland17 0:7f4ed364f7ea 39 else{
thomasosullivan 2:6077294f7007 40 lcd.locate(0,1);
thomasosullivan 2:6077294f7007 41 lcd.printf("%u Ω", runknown); // prints on the second row of the LCD screen
decland17 0:7f4ed364f7ea 42 }
decland17 0:7f4ed364f7ea 43 break;
decland17 0:7f4ed364f7ea 44
thomasosullivan 2:6077294f7007 45 case 5500: // this case is for if R is in a different range
decland17 0:7f4ed364f7ea 46 vt = 0.0189;
decland17 0:7f4ed364f7ea 47 100ohm = 1;
decland17 0:7f4ed364f7ea 48 1kohm = 0;
decland17 0:7f4ed364f7ea 49 vout = (3.3 * vo)/ 4095;
decland17 0:7f4ed364f7ea 50 runknown = (vout * 1000) / (3.3 - vt - vout);
decland17 0:7f4ed364f7ea 51 lcd.locate(0,1);
decland17 0:7f4ed364f7ea 52 if (runknown < 1000){
thomasosullivan 2:6077294f7007 53 lcd.printf("%u Ω", runknown);
thomasosullivan 2:6077294f7007 54 } // this if correct runknown to the appropriate magnitude
decland17 0:7f4ed364f7ea 55 else {
thomasosullivan 2:6077294f7007 56 runknown = runknown / 1000; //runkown is now printed in KΩ
decland17 0:7f4ed364f7ea 57 lcd.printf("%.2f kΩ", runknown);
decland17 0:7f4ed364f7ea 58 break;
decland17 0:7f4ed364f7ea 59
decland17 0:7f4ed364f7ea 60 case 55000:
decland17 0:7f4ed364f7ea 61 vt = 0.0075148;
decland17 0:7f4ed364f7ea 62 100ohm = 1;
decland17 0:7f4ed364f7ea 63 10kohm = 0;
decland17 0:7f4ed364f7ea 64 vout = (3.3 * vo)/ 4095;
decland17 0:7f4ed364f7ea 65 runknown = (vout * 10000) / (3.3 - vt - vout);
decland17 0:7f4ed364f7ea 66 lcd.locate(0,1);
decland17 0:7f4ed364f7ea 67 runknown = runknown / 1000;
decland17 0:7f4ed364f7ea 68 lcd.printf("%.2f kΩ", runknown);
decland17 0:7f4ed364f7ea 69 break;
decland17 0:7f4ed364f7ea 70
decland17 0:7f4ed364f7ea 71 case 550000:
decland17 0:7f4ed364f7ea 72 vt = 0.00612;
decland17 0:7f4ed364f7ea 73 100ohm = 1;
decland17 0:7f4ed364f7ea 74 100kohm = 0;
decland17 0:7f4ed364f7ea 75 vout = (3.3 * vo)/ 4095;
decland17 0:7f4ed364f7ea 76 runknown = (vout * 100000) / (3.3 - vt - vout);
decland17 0:7f4ed364f7ea 77
decland17 0:7f4ed364f7ea 78 lcd.locate(0,1);
decland17 0:7f4ed364f7ea 79
decland17 0:7f4ed364f7ea 80 if (runknown < 1000000){
decland17 0:7f4ed364f7ea 81 runknown = runknown / 1000;
decland17 0:7f4ed364f7ea 82 lcd.printf("%.2f kΩ", runknown);
decland17 0:7f4ed364f7ea 83 }
decland17 0:7f4ed364f7ea 84 else {
thomasosullivan 2:6077294f7007 85 runknown = runknown / 1000000; // this will change the magnitude to MΩ
decland17 0:7f4ed364f7ea 86 lcd.printf("%.2f MΩ", runknown);
decland17 0:7f4ed364f7ea 87 break;
decland17 0:7f4ed364f7ea 88
decland17 0:7f4ed364f7ea 89 case 5500000:
decland17 0:7f4ed364f7ea 90 vt = 0.0059684;
decland17 0:7f4ed364f7ea 91 100ohm = 1;
decland17 0:7f4ed364f7ea 92 1Mohm = 0;
decland17 0:7f4ed364f7ea 93 vout = (3.3 * vo)/ 4095;
decland17 0:7f4ed364f7ea 94 runknown = (vout * 1000000) / (3.3 - vt - vout);
decland17 0:7f4ed364f7ea 95
decland17 0:7f4ed364f7ea 96 lcd.locate(0,1);
decland17 0:7f4ed364f7ea 97 runknown = runknown / 1000000;
decland17 0:7f4ed364f7ea 98 lcd.printf("%.2f MΩ", runknown);
decland17 0:7f4ed364f7ea 99 break;
decland17 0:7f4ed364f7ea 100
decland17 0:7f4ed364f7ea 101 case 10000000:
decland17 0:7f4ed364f7ea 102 vt = 0.0059526;
decland17 0:7f4ed364f7ea 103 100ohm = 1;
decland17 0:7f4ed364f7ea 104 10Mohm = 0;
decland17 0:7f4ed364f7ea 105 vout = (3.3 * vo)/ 4095;
decland17 0:7f4ed364f7ea 106 runknown = (vout * 10000000) / (3.3 - vt - vout);
decland17 0:7f4ed364f7ea 107
decland17 0:7f4ed364f7ea 108 lcd.locate(0,1);
decland17 0:7f4ed364f7ea 109 runknown = runknown / 1000000;
decland17 0:7f4ed364f7ea 110 lcd.printf("%.2f MΩ", runknown);
decland17 0:7f4ed364f7ea 111 break;
decland17 0:7f4ed364f7ea 112
decland17 0:7f4ed364f7ea 113 default:
decland17 0:7f4ed364f7ea 114 lcd.locate(0,1);
thomasosullivan 2:6077294f7007 115 lcd.printf("Out of Range"); // this will apear if runkown is outside the design parameters
decland17 0:7f4ed364f7ea 116 break;
decland17 0:7f4ed364f7ea 117
decland17 0:7f4ed364f7ea 118 }