K-type Arduino Thermometer

Hi all,
Recently I had to measure the temperature in a place where ordinary temp sensors like LM35 or TMP36 wouldn't fit. And not only this but the temperature was many degrees below zero. To be precise -70c to -80c. Traditional sensors are not working below -50c so the solution I came up was to use a k-type thermocouple. In order to make arduino read the k-type thermocouple values I had to use a Thermocouple-to-Digital Converter. Thankfully Adafruit is selling MAX31855 in good price and also you can download an Arduino library from them. What more can you ask?

Step 1: Schematic

The schematic of the circuit is very simple. As you can see the Max31855 except the volt and ground has three more pins. The DO, the CS and CLK. I connected those to Arduino D5,D4 and D3 respectively. Then the only thing that was left was to connect the LCD. As you can see in the schematic LCD uses 6 pins from Arduino. For the lcd i used the LiquidCrystal library which comes with the Arduino IDE, so no need to download.

Step 2: Arduino Code

Last step was to upload the code to Arduino. Code is available here. All went smooth and temperature showed up to the lcd.
Here is a small video:
Thanks for reading and good luck!

Comments

[MichaelM50]

Hi, how do I change celcuis to fahenheit using the file downloaded for your link to GitHub?

[CoalaWeb]

You can change the line:

double c = thermocouple.readCelsius();

to

double c = thermocouple.readFahrenheit();

Hope that helps.

Ref:

https://learn.adafruit.com/thermocouple/arduino-code

[eroche100]

Thanks for sharing. You stated that you had success reading down to -80 deg C... Do you know if the Arduino is able to support the full range of the type K thermocouple (which I believe goes up to from -200 deg C to 1260 deg C)?

Many thanks!

[unseen1980]

Hi,

I don't see why it can't read down to -196. Arduino acts like the middle man between the Max31855 and the display. Good luck!

[unseen1980]

Sorry guys, some issues with azure. Link is up.

http://www.devacron.com/k-type-thermometer-lcd-arduino-nano/

[jfm8561]

Thanks you for sharing your project! I am having an accuracy issues, in a 70 degree F room the thermocouple is reading around 107 degrees, and I did change read celsuis to read farenheight. Thanks in advance.

[Woodfield1]

I'm having the same issue. Did you find a fix?

[f-bone]

The code as found in Google cached page:

(http://webcache.googleusercontent.com/search?q=cache:qrqakUdqLtQJ:www.devacron.com/k-type-thermometer-lcd-arduino-nano/+&cd=1&hl=el&ct=clnk&gl=gr)

And the Arduino code which is making use of library Adafruit-MAX31855-library

#include "Adafruit_MAX31855.h" 
#include <LiquidCrystal.h> 

int thermoCLK = 3; 
int thermoCS = 4; 
int thermoDO = 5; 

// Initialize the Thermocouple 
Adafruit_MAX31855 thermocouple(thermoCLK, thermoCS, thermoDO); 
// initialize the library with the numbers of the interface pins 
LiquidCrystal lcd(7, 8, 9, 10, 11, 12); 

void setup() { 
  Serial.begin(9600); 
  lcd.begin(16, 2);   
  lcd.print("MAX31855 Init"); 
  delay(500); 
} 

void loop() { 
  // basic readout test, just print the current temp 
   lcd.setCursor(0, 0); 
   lcd.print("www.devacron.com"); 
   lcd.print("  ");  

   double c = thermocouple.readCelsius(); 
   lcd.setCursor(0, 1); 
   if (isnan(c))  
   { 
     lcd.print("T/C Problem"); 
   }  
   else  
   { 
     lcd.print("Temp = ");  
     lcd.print(c); 
     lcd.print("c");  
   } 

   delay(1000); 
} 

[pintail120]

Hi,
the link for the code is broken

[will_raymo2000]

Would it be possible to increase the number of inputs to 4 on this project? I understand I'd need separate ADC for each thermocouple but how would I then interface these with the Arduino so the display shows T1: T2: etc etc?

Cheers