Thermal conversion

Projects Programming
1

I'm attempting to construct a plant watering and monitoring system using an arduino. I'm using an existing layout and program.
The output to the LCD display from the 10k Thermistor is as follows:

Temp output
61°F = 901
90°F = 949
51°F = 877
32°F = 796

I've been trying to write some lines to convert the output to read degrees farenheit. Any help would be appreciated.

CODE:
int moistureSensor = 0;
int lightSensor = 1;
int tempSensor = 2;
int moisture_val;
int light_val;
int temp_val;
void setup() {
Serial.begin(9600); //open serial port
}
void loop() {
moisture_val = analogRead(moistureSensor); // read the value from the moisture-sensing probes
Serial.print("moisture sensor reads ");
Serial.println( moisture_val );
delay(500);
light_val = analogRead(lightSensor); // read the value from the photosensor
Serial.print("light sensor reads ");
Serial.println( light_val );
delay(500);
temp_val = analogRead(tempSensor); // read the value from the thermistor
Serial.print("temp sensor reads ");
Serial.println( temp_val );
delay(1000);
}

TNX Buzz239

2

To get the temperature properly from a thermistor, do it by this tutorial. You will need spec sheet of your thermistor or need to calculate for a few constants. The values, as you can see, are not linear so map is not accurate.

3

If you try that with 70K, which is about room temperature, you can be off from even the crude 4-point curve by 15F. I don't think it's very useful if you are off by that much. We are not talking about 0.x degrees.

4

Especially for such non-linear mapping I wrote multiMap() a while ago - Arduino Playground - MultiMap -.

You should check how many points you need for an acceptable error / precision. Note that the in[] array does not need to be equidistant between the points.