A standard DHT or LM35 sensor tops out at temperatures your hand could touch — a K-type thermocouple paired with a MAX6675 module reads well past that, into the hundreds of degrees Celsius, which is what you actually need for things like soldering irons, ovens, or furnaces.
Why a thermocouple needs a special module
A K-type thermocouple itself is just two different metal wires joined at a tip, producing a tiny voltage that changes with temperature — far too small and noisy for Arduino's analog pins to read directly. The MAX6675 module handles this: it amplifies that microvolt-level signal, applies cold-junction compensation to correct for the temperature at the connector itself, and converts the result into a clean digital reading over SPI.
Components needed
An Arduino Uno, a MAX6675 thermocouple amplifier module, a K-type thermocouple probe, and jumper wires.
Wiring it up
The MAX6675 communicates over SPI: VCC to 5V, GND to ground, and then SCK, CS, and SO connected to any three digital pins (commonly 5, 4, and 6, defined in code rather than fixed by hardware). The thermocouple probe itself plugs into the module's screw terminals, matching polarity.
Programming it
The MAX6675 library initializes the module with the three chosen pins, then a single function call returns the temperature directly in Celsius (or Fahrenheit with a simple conversion), which the sketch prints to the Serial Monitor or shows on an LCD.
What it is actually good for
The MAX6675 reports approximately 0.25°C steps and has a nominal range to 1024°C, but usable range and accuracy are also limited by the selected thermocouple probe, insulation, and installation. Keep the cold junction away from the hot zone, respect polarity and noise control, and handle the open-thermocouple indication.
You can find MAX6675 thermocouple modules and K-type probes at Juthour Tech.
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