2017 REVIEW | 'IoT & Embedded MAKER SPACE - MKE' Group
MAX6675 Temp Module & Arduino
2017 OCTOBER | by Gene Casanova
Senior Systems Engineer
K Thermalcoupler & Arduino
Thermocouples are an industrial standard for accuracy measuring temperature. Thermocouples are made in a wide range of physical configurations and measuring capabilities.
Cold junction compensation and detection of a very small voltage change, for every degree in change of temperature, are parameters required to get accurate measurements.
The MAX6675 IC chip, offers K type thermocouple functionality with an Arduino system. The IC has been designed to measure the output from a K thermocouple, and output the data through a 'SPI' interface. This SPI interface is ready to use on an Arduino systemboard.
The MAX6675 performs cold-junction compensation and digitizes the signal from a type-K thermocouple. The data is output in a 12-bit resolution, SPI™-compatible, read-only format. This converter resolves temperatures to 0.25°C, enabling readings as high as +1024°C, and exhibits thermocouple accuracy of 8LSBs for temperatures ranging from 0°C to +700°C.
Applications ● Industrial ● Appliances ● HVAC
● Direct Digital Conversion of Type -K Thermocouple Output
● Cold-Junction Compensation
● Simple SPI-Compatible Serial Interface
● 12-Bit, 0.25°C Resolution
● Open Thermocouple Detection
MAX6675ISA -20°C to +85°C, 8 SO package.
MAX6675 Specifications
Supply Voltage | 3.3VDC to 5 VDC |
---|---|
Operating Current | ~ 50mA |
Measurement Range | 0 to 1024 deg C (32 deg F to 1875 F) |
Measurement Resolution | 3.3VDC to 5 VDC+/- 0.25 Deg C (+/- 0.45 Deg F) |
Output | SPI Interface |
SENSOR | External: K Thermalcoupler |
CGI Computer Wares MAX6675 Module Pinouts
- SO
- Serial Output
- CS
- Chip Select. Set 'LOW', selects the module and triggers an output synchronized with a clock.
- SCK
- Serial Clock. Provided by an Arduino systemboard.
- VCC
- 5 VDC. Typically provided by 5V output pin on Arduino systemboard.
- GND
- Ground. Provided by an Arduino systemboard.
- -
- Negative terminal of K Thermalcoupler.
- +
- Positive terminal of K Thermalcoupler.
K Thermalcouplers Color Code
BEWARE: Most K thermocouples come with a red lead and a yellow lead.
The red lead is normally the negative (-) connection; the yellow lead is positive (+); as an thermalcoupler-industry standard.
Thermalcoupler connections test - increase the temperature at the thermocouple tip. Correct lead connection polarity, will provide an increase in temperature indication. An incorrect (reversed) lead connection polarity will indicate a decreasing temperature.
CGI Computer Wares MAX6675 Module Arduino Sketch (C Source Code)
An Experimental Arduino Sketch and connection configuration:
Arduino ---> Module
pin 10 ---> SCK
pin 9 ---> CS
pin 8 ---> SO
5V ---> VCC
GND ---> GND
/* EXPERIMENTAL * MAX6675 Arduino Termperature Reading */ #include "max6675.h" int ktcSO = 8; int ktcCS = 9; int ktcCLK = 10; MAX6675 ktc(ktcCLK, ktcCS, ktcSO); void setup(){ Serial.begin(9600); // Delay, enabling the MAX6675 establish steady data delay(500); } void loop(){ // Basic Serial Output Test: Serial.print("Deg C = "); Serial.print(ktc.readCelsius()); Serial.print("\t Deg F = "); Serial.println(ktc.readFahrenheit()); delay(500); // Delay. }
Use The Technology Wisely & Keep It Simple
- Cheers!
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CGI Computer Wares | EST 1979
