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The circuit here is a simplification of what the code below is for. If you would like to use the code below, use an Arduino, two BCD's and two 7 Segment displays, Thermistor, resistor and an op amp. If you have questions, feel free to ask.
The code below samples the voltage across a Thermistor and then uses this voltage to calculate temperature. The temperature (F) is then rounded to the nearest two digits and printed on the 7 segment displays.
My Parts list:
Arduino UNO or Nano microcontroller.
lds-c514ri Seven Segment Display.
hd74ls48p BCD.
LT1006 Opamp.
Antique Thermistor.
56k ohm resistor.
const bool bcd[11][40] = {{0,0,0,0}, //DCBA --> 0
{0,0,0,1}, //DCBA --> 1
{0,0,1,0}, //DCBA --> 2
{0,0,1,1}, //DCBA --> 3
{0,1,0,0}, //DCBA --> 4
{0,1,0,1}, //DCBA --> 5
{0,1,1,0}, //DCBA --> 6
{0,1,1,1}, //DCBA --> 7
{1,0,0,0}, //DCBA --> 8
{1,0,0,1}, //DCBA --> 9
{1,1,1,1}}; //DCBA --> 10 "blank"
const int pin = 0;
const float res = 0.00471261;
//const float To = 293.00;
const float To = 298.00;
const float Ro = 50000.0;
//const float beta = 5066.0; //Beta for Antique Thermistor
const float beta = 3095.0; //Beta for MF52C1503F3950
const float numSample = 10.0;
void writeToBCD1(int);
void writeToBCD2(int);
float getTempFar();
void setup() {
Serial.begin(9600);
pinMode(pin, INPUT);
pinMode(2, OUTPUT); //D1 --> pin2
pinMode(3, OUTPUT); //C1 --> pin3
pinMode(4, OUTPUT); //B1 --> pin4
pinMode(5, OUTPUT); //A1 --> pin5
pinMode(6, OUTPUT); //D2 --> pin6
pinMode(7, OUTPUT); //C2 --> pin7
pinMode(8, OUTPUT); //B2 --> pin8
pinMode(9, OUTPUT); //A2 --> pin9
}
void loop() {
int i = 0;
float tempFarAvg = 0;
while(i < numSample) {
tempFarAvg += getTempFar();
i++;
delay(7);
Serial.print("Sample: "); Serial.println(i);
}
int rounded = round(tempFarAvg/numSample);
Serial.print("Rounded temp = "); Serial.println(rounded);
if(rounded < 0) {
writeToBCD1(0);
writeToBCD2(0);
}
else if(rounded > 0 && rounded < 10) {
writeToBCD1(10);
writeToBCD2(rounded);
}
else if(rounded >= 100) {
writeToBCD1(9);
writeToBCD2(9);
}
else {
int firstDig = rounded/10;
writeToBCD1(firstDig);
int subtractor = firstDig*10;
int secDig = rounded - subtractor;
writeToBCD2(secDig);
}
}
void writeToBCD1(int msd) {
for(int i = 0; i < 4; i++) {
digitalWrite(i + 2, bcd[msd][i]);
}
}
void writeToBCD2(int lsd) {
for(int i = 0; i < 4; i++) {
digitalWrite(i + 6, bcd[lsd][i]);
}
}
float getTempFar() {
float volt = analogRead(pin)*res;
float Rdel = 50470/((4.596/volt)-1);
float tempKel = (To*beta)/(To*log(Rdel/Ro)+beta);
float tempFar = (9.0/5.0)*(tempKel-273) + 32;
return(tempFar);
}
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