Phone Thermometer

1#define R25 470.0f
2#define RKNOWN 4700.0f
3#define RWIRE 0.2f
4#define
5  ARRAY_SIZE 34
6
7// from datasheet
8float Array_RT[] = {9573.90f, 7245.52f,
9  5534.25f, 4262.81f, 3313.36f, 2593.79f, 2047.23f, 1626.62f, 1302.14f, 1048.71f,
10  850.61f, 693.81f, 569.45f, 470.00f, 390.02f, 325.33f, 272.80f, 229.83f, 194.56f,
11  165.43f, 141.28f, 121.17f, 104.33f, 90.19f, 78.25f, 68.14f, 59.54f, 52.21f, 45.93f,
12  40.53f, 35.87f, 31.85f, 28.35f, 25.31f};
13float Array_T[] = {-40.0f, -35.0f, -30.0f,
14  -25.0f, -20.0f, -15.0f, -10.0f, -5.0f, 0.0f, 5.0f, 10.0f, 15.0f, 20.0f, 25.0f, 30.0f,
15  35.0f, 40.0f, 45.0f, 50.0f, 55.0f, 60.0f, 65.0f, 70.0f, 75.0f, 80.0f, 85.0f, 90.0f,
16  95.0f, 100.0f, 105.0f, 110.0f, 115.0f, 120.0f, 125.0f};
17
18int a7;
19
20float
21  RT;
22float T = -273.15;
23
24int idx1, idx2;
25
26void setup() {
27  Serial.begin(19200);
28
29  
30  pinMode(LED_BUILTIN, OUTPUT);
31  
32  // blink fast to indicate startup
33  / reset
34  for (int i=0; i<5; i++){
35    digitalWrite(LED_BUILTIN, HIGH);
36
37    delay(50);
38    digitalWrite(LED_BUILTIN, LOW);
39    delay(50);
40  }  
41}
42
43void
44  loop() {
45  digitalWrite(LED_BUILTIN, HIGH);
46  delay(1000);
47
48  a7 = analogRead(7);
49  // 10 bit => a7  [0..1023]
50
51  // example 2 bit  : a7  [0..3]    => 0 == 0
52  * 5/3 V,    1 == 1 * 5/3V , 2 == 2 * 5/3 V, 3 == 3 * 5/3 V
53  // example 10 bit
54  : a7  [0..1023] => 0 == 0 * 5/1023 V, 1 == 1 * 5/1023 V, ..., 1023 == 1023 * 5/1023
55  V
56  
57  // https://en.wikipedia.org/wiki/Voltage_divider (Resistive divider)
58
59  // a7 = 1023 * RKNOWN / (RT + RKNOWN)
60  // => (RT + RKNOWN) = 1023 * RKNOWN
61  / a7
62  // => RT = 1023 * RKNOWN / a7 - RKNOWN
63  // => RT = RKNOWN * (1023
64  / a7 - 1)
65  
66  RT = RKNOWN * (1023.0f / (float)a7 - 1.0f) + RWIRE;
67    
68
69  for (int i=1; i < ARRAY_SIZE; i++) {
70    if (Array_RT[i] < RT){
71      idx1
72  = i - 1;
73      idx2 = i;  
74      break;          
75    }
76  }
77    
78
79  T = (Array_T[idx2] - Array_T[idx1]) / (Array_RT[idx2] - Array_RT[idx1]) * (RT
80  - Array_RT[idx1]) + Array_T[idx1];    
81
82  /*Serial.print("a7: "); Serial.print(a7);
83  Serial.print(" ");
84  Serial.print("RT: "); Serial.print(RT); Serial.print("
85  ");
86  Serial.print("idx1: "); Serial.print(idx1); Serial.print(" ");
87
88  Serial.print("idx2: "); Serial.print(idx2); Serial.print(" ");
89  Serial.print("Array_RT[idx1]:
90  "); Serial.print(Array_RT[idx1]); Serial.print(" ");
91  Serial.print("Array_RT[idx2]:
92  "); Serial.print(Array_RT[idx2]); Serial.print(" ");
93  Serial.print("Array_T[idx1]:
94  "); Serial.print(Array_T[idx1]); Serial.print(" ");
95  Serial.print("Array_T[idx2]:
96  "); Serial.print(Array_T[idx2]); Serial.print(" ");
97  Serial.print("T: ");
98  Serial.print(T); Serial.print(" ");
99  Serial.print("round(T): "); Serial.print(round(T));
100  Serial.print(" ");*/
101  Serial.println(round(T));
102  
103    
104  digitalWrite(LED_BUILTIN,
105  LOW);
106  delay(1000);
107   
108  
109}
110

1#define R25 470.0f
2#define RKNOWN 4700.0f
3#define RWIRE 0.2f
4#define  ARRAY_SIZE 34
5
6// from datasheet
7float Array_RT[] = {9573.90f, 7245.52f,  5534.25f, 4262.81f, 3313.36f, 2593.79f, 2047.23f, 1626.62f, 1302.14f, 1048.71f,  850.61f, 693.81f, 569.45f, 470.00f, 390.02f, 325.33f, 272.80f, 229.83f, 194.56f,  165.43f, 141.28f, 121.17f, 104.33f, 90.19f, 78.25f, 68.14f, 59.54f, 52.21f, 45.93f,  40.53f, 35.87f, 31.85f, 28.35f, 25.31f};
8float Array_T[] = {-40.0f, -35.0f, -30.0f,  -25.0f, -20.0f, -15.0f, -10.0f, -5.0f, 0.0f, 5.0f, 10.0f, 15.0f, 20.0f, 25.0f, 30.0f,  35.0f, 40.0f, 45.0f, 50.0f, 55.0f, 60.0f, 65.0f, 70.0f, 75.0f, 80.0f, 85.0f, 90.0f,  95.0f, 100.0f, 105.0f, 110.0f, 115.0f, 120.0f, 125.0f};
9
10int a7;
11
12float  RT;
13float T = -273.15;
14
15int idx1, idx2;
16
17void setup() {
18  Serial.begin(19200);
19  
20  pinMode(LED_BUILTIN, OUTPUT);
21  
22  // blink fast to indicate startup  / reset
23  for (int i=0; i<5; i++){
24    digitalWrite(LED_BUILTIN, HIGH);
25    delay(50);
26    digitalWrite(LED_BUILTIN, LOW);
27    delay(50);
28  }  
29}
30
31void  loop() {
32  digitalWrite(LED_BUILTIN, HIGH);
33  delay(1000);
34
35  a7 = analogRead(7);  // 10 bit => a7  [0..1023]
36
37  // example 2 bit  : a7  [0..3]    => 0 == 0  * 5/3 V,    1 == 1 * 5/3V , 2 == 2 * 5/3 V, 3 == 3 * 5/3 V
38  // example 10 bit  : a7  [0..1023] => 0 == 0 * 5/1023 V, 1 == 1 * 5/1023 V, ..., 1023 == 1023 * 5/1023  V
39  
40  // https://en.wikipedia.org/wiki/Voltage_divider (Resistive divider)
41  // a7 = 1023 * RKNOWN / (RT + RKNOWN)
42  // => (RT + RKNOWN) = 1023 * RKNOWN  / a7
43  // => RT = 1023 * RKNOWN / a7 - RKNOWN
44  // => RT = RKNOWN * (1023  / a7 - 1)
45  
46  RT = RKNOWN * (1023.0f / (float)a7 - 1.0f) + RWIRE;
47    
48  for (int i=1; i < ARRAY_SIZE; i++) {
49    if (Array_RT[i] < RT){
50      idx1  = i - 1;
51      idx2 = i;  
52      break;          
53    }
54  }
55    
56  T = (Array_T[idx2] - Array_T[idx1]) / (Array_RT[idx2] - Array_RT[idx1]) * (RT  - Array_RT[idx1]) + Array_T[idx1];    
57
58  /*Serial.print("a7: "); Serial.print(a7);  Serial.print(" ");
59  Serial.print("RT: "); Serial.print(RT); Serial.print("  ");
60  Serial.print("idx1: "); Serial.print(idx1); Serial.print(" ");
61  Serial.print("idx2: "); Serial.print(idx2); Serial.print(" ");
62  Serial.print("Array_RT[idx1]:  "); Serial.print(Array_RT[idx1]); Serial.print(" ");
63  Serial.print("Array_RT[idx2]:  "); Serial.print(Array_RT[idx2]); Serial.print(" ");
64  Serial.print("Array_T[idx1]:  "); Serial.print(Array_T[idx1]); Serial.print(" ");
65  Serial.print("Array_T[idx2]:  "); Serial.print(Array_T[idx2]); Serial.print(" ");
66  Serial.print("T: ");  Serial.print(T); Serial.print(" ");
67  Serial.print("round(T): "); Serial.print(round(T));  Serial.print(" ");*/
68  Serial.println(round(T));
69  
70    
71  digitalWrite(LED_BUILTIN,  LOW);
72  delay(1000);
73   
74  
75}
76