Thermocouple Amplifier MAX6675, SN-6675

In this tutorial, you will going to learn on how to interface this product with SK40C and BBFUINO with Thermocouple K in order to measure the temperature. The sample source code was attached at the end of this tutorial.

In order to measure the temperature without using the thermometer, thermocouples are the option to do so. However, the thermocouples need a reference temperature(normally take 0°C ) as to detect the difference of the temperature in between the materials of the thermocouples and is very inconvenience for the user to use it. Hence, SN-6675 is introduced to do everything for you.This SN-6675 breakout board comes along with MAX6675 and a bypass capacitor.


  • Works with K type thermocouple
  • 0°C to +1024C output in 0.25 degree increments
  • Internal temperature reading
  • SPI data output requires any 3 digital I/O pins.


  • VCC – 3.3 to 5v power supply and logic level compliant!
  • CS – Active low to enable the chip
  • SO – reads out the 12-bit result onto this pin(Connect to SDI pin)
  • SCK – Provide the clock pulse (Connect to SCK pin)
  • T- – Connected the the T- of the thermocouple
  • T+ – Connected to the T+ of the thermocouple

In this tutorial, you will learn on how to interface this product with SK40C and the Thermocouple K in order to measure the temperature. The sample source code is attached at the end of this tutorial.


 1 x SK40C                     1 x SN-6675              1 x Serial LCD (2×16)           
 1 x BBFuino                           1 x LCD (8×2)                     1 x Header Pin (2×20)          
    1 x IC PIC 16F887                     1 x Terminal Block-2 Way         1 x Straight Pin Header (Male) 
male to male jumper wire
 Male to Male Jumper Wire                 1 x Breadboard              1 x Thermocouple K



1. First of all, solder the 2 ways terminal block and straight pin header to the SN-6675.
                            Front view                                                            Back view

                          Figure 1: Soldered the block terminal  and pin header to SN-6675

2. Next. connect the component to the SK40C on a breadboard  as the schematic and the sample circuit connection provided

                                                Figure 1.1: Schematic (Click to enlarge)


                                   Figure 1.2: Actual Circuit connection (Click to enlarge)


                               Figure 1.3: Sample Circuit Connection (Click to enlarge)

3. The following show some part of the sample source code..
    The microcontroller used for this tutorial is PIC16F887.
    The MPlab X version 1.20 and XC8 compiler version 1.0 can be downloaded from here
    Please refer here for MPlab X tutorial
main function: This function was functioning as to read the temperature from the SN-6675
[sourcecode language=”cpp” wraplines=”true”]
obtain = 0;
obtain = readCelsius();
data = obtain%100;
obtain = obtain/100;
lcd_bcd(3, obtain);
lcd_bcd(2, data);
RB7 ^= 1;

Sub-function: Since the MAX6675 receive 12 bits of data at once, this function detects the data received by shifting the bits received as much as 16 times before sending it back to PIC16F887. The following code shows the virtual SPI function generating the clock pulse 16 times in order to receive the data in 16 bits.

[sourcecode language=”cpp” wraplines=”true”]
unsigned int readCelsius(void) {

unsigned int v;

CS = 0;

v = spiread();
v <<= 8;
v |= spiread();
CS = 1;

v >>= 3;
return v*25;

unsigned char spiread(void) {
int i;
unsigned char d = 0;

for (i=7; i>=0; i–)
SCK = 0;
if (SO) {
//set the bit to 0 no matter what
d |= (1 << i);
SCK = 1;

return d;

7.Observed the temperature changed.                      

Figure 2.8: Room Temperature_Night(Click to enlarge)

Figure 2.9: Temperature change as Thermocouple K detect the heat change

 8. Done 



11 thoughts on “Thermocouple Amplifier MAX6675, SN-6675”

  1. hye…..

    i would like to ask if im using hyper terminal. do u have a sample of the source code.

    thank you.

  2. Pls, can i get a source code on hi-tech picc for temperature, keypad and lcd interface ie their initialization. i tried writing the code using mikroc pro but it keep telling me demo limit. am now trying to switch to hi-tech c.

  3. do you have any sensor that suitable for cooking oil measurement?i dont know what type of sensor that suitable

  4. Not really recommend if the cooking oil is for human consumption. We do not know the reaction of the insulator on thermocouple to cooking oil and what is the chemical reaction

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