/* * Detector Building * Code by Anthony Wang * Ladue High School Science Olympiad */ /* * TODO: * BUG FIXING: Expect bugs! */ // Constants const bool CALIB = false; // Calibration mode const int LED_R = 4, LED_G = 3, LED_B = 2, THERM = 0; // Device component pins const double R_k = 10000, V_in = 5, analog_max = 1023; // Device constants // Calibration data const int n = 3, m = n / 3; // Number of data points, MUST be multiple of 3 double V[n] = { 2.12, 3.26, 3.96 }; // Voltage measurements double T[n] = { 22.0, 39.15, 60 }; // Temperature measurements double V_mid[m]; // Stores each piecewise segment for binary search double A[m], B[m], C[m]; // Coefficients for each piecewise component // Temperature conversions inline double f2c(double f) { return (f - 32) * 5 / 9; } // Fahrenheit to Celsius inline double c2f(double c) { return c * 9 / 5 + 32; } // Celsius to Fahrenheit inline double k2c(double k) { return k - 273.15; } // Kelvin to Celsius inline double c2k(double c) { return c + 273.15; } // Celsius to Kelvin inline double f2k(double f) { return c2k(f2c(f)); } // Fahrenheit to Kelvin inline double k2f(double k) { return c2f(k2c(k)); } // Kelvin to Fahrenheit // Analog to digital conversion inline double a2d(int a) { return V_in * a / analog_max; } inline int d2a(double d) { return d * analog_max / V_in; } // Utility functions // No C++ standard library :( void sort(double a[], int n) { // Bubble sort // Slow but n < 30 so OK // Too lazy to implement a fast sort for (int i = 0; i < n; i++) { for (int j = 0; j < n - 1; j++) { if (a[j] > a[j + 1]) { double tmp = a[j]; a[j] = a[j + 1]; a[j + 1] = tmp; } } } } // Calculations // Steinhart-hart stuff void calculate() { sort(V, n); sort(T, n); double R[n], L[n], Y[n], G[n]; for (int i = 0; i < n; i++) R[i] = R_k * (V_in / V[i] - 1); for (int i = 0; i < n; i++) L[i] = log(R[i]); for (int i = 0; i < n; i++) Y[i] = 1 / c2k(T[i]); for (int i = 0; i < n; i += 3) { G[i + 1] = (Y[i + 1] - Y[i]) / (L[i + 1] - L[i]); G[i + 2] = (Y[i + 2] - Y[i]) / (L[i + 2] - L[i]); } for (int i = 0; i < n; i += 3) { // Don't ask how this works C[i / 3] = (G[i + 2] - G[i + 1]) / (L[i + 2] - L[i + 1]) / (L[i] + L[i + 1] + L[i + 2]); B[i / 3] = G[i + 1] - C[i / 3] * (L[i] * L[i] + L[i] * L[i + 1] + L[i + 1] * L[i + 1]); A[i / 3] = Y[i] - L[i] * (B[i / 3] + L[i] * L[i] * C[i / 3]); } for (int i = 0; i < n; i += 3) V_mid[i / 3] = (i ? (V[i - 1] + V[i]) / 2 : V[i]); } // Arduino stuff void blink(int pin) { digitalWrite(pin, HIGH); delay(1000); digitalWrite(pin, LOW); } // More Arduino stuff void setup() { Serial.begin(9600); pinMode(LED_R, OUTPUT); pinMode(LED_G, OUTPUT); pinMode(LED_B, OUTPUT); // blink(LED_R); // blink(LED_G); // blink(LED_B); calculate(); // Debug stuff /*for (int i = 0; i < n; i++) { Serial.print(V[i]); Serial.print(" "); Serial.print(T[i]); Serial.print(" "); } Serial.println(); for (int i = 0; i < m; i++) { Serial.print("Segment lower bound: "); Serial.print(i ? V_mid[i - 1] : 0); Serial.print(" Segment upper bound: "); Serial.print(V_mid[i]); Serial.print(" A: "); Serial.print(A[i], 12); Serial.print(" B: "); Serial.print(B[i], 12); Serial.print(" C: "); Serial.print(C[i], 12); Serial.println(); }*/ } // Main loop void loop() { int V_raw = analogRead(THERM); // Read in raw analog value double V_out = a2d(V_raw); // Convert analog to digital double R_t = R_k * (V_in / V_out - 1); // Thermistor resistance if (CALIB) { // Calibration mode Serial.print("Raw analog reading: "); Serial.print(V_raw); Serial.print(" Voltage (V): "); Serial.print(V_out); Serial.println(); delay(500); return; } int s = 0; while (s + 1 < m && V_out > V_mid[s + 1]) s++; // Find correct segment double logR_t = log(R_t); double K = 1.0 / (A[s] + B[s] * logR_t + C[s] * logR_t * logR_t * logR_t); // Steinhart-hart double C = k2c(K); double F = c2f(C); // LED stuff if (C <= 25) { // Cold digitalWrite(LED_R, LOW); digitalWrite(LED_G, LOW); digitalWrite(LED_B, HIGH); } else if (C <= 50) { // Medium digitalWrite(LED_R, LOW); digitalWrite(LED_G, HIGH); digitalWrite(LED_B, LOW); } else if (C <= 75) { // Hot digitalWrite(LED_R, HIGH); digitalWrite(LED_G, LOW); digitalWrite(LED_B, LOW); } else { // Something seriously wrong digitalWrite(LED_R, HIGH); digitalWrite(LED_G, HIGH); digitalWrite(LED_B, HIGH); } // Output voltage, temperature Serial.print("Raw analog reading: "); Serial.print(V_raw); Serial.print(" Voltage (V): "); Serial.print(V_out); //Serial.print(" Resistance (Ohms): "); //Serial.print(R_t); Serial.print(" Temperature (°C): "); Serial.print(C); // For reference //Serial.print(" Temperature (°F): "); //Serial.print(F); // Debug stuff /*Serial.print(" Segment lower bound: "); Serial.print(s ? V_mid[s - 1] : 0); Serial.print(" Segment upper bound: "); Serial.print(V_mid[s]);*/ Serial.println(); delay(500); return; }