Mike's Workshop Notebook

Pyrometer

To improve casting results, I needed a reliable way to measure melt temperature used to determine the optimal time to pour. Since brass and bronze melt at approximately 1,000°C (1,800°F), standard temperature probes are not suitable for this range. The solution is a high-temperature thermometer, or pyrometer. For this setup, I chose to build my own.

Photos

CNC Mill Pic
The completed pyrometer with an 18" thermocouple wand. The extended probe length makes it easy to reach into the melt while maintaining a safe working distance. The meter performs well, displaying temperature in both Celsius and Fahrenheit, and includes an elapsed time function that helps track and characterize the time to pouring temperature.
CNC Mill Pic
Here is a view of the pyrometer components. The unit is built around an Arduino Pro processor board (SparkFun.com), which provides more than enough capability for this application. Its SPI interfaces are used to communicate with both the thermocouple amplifier and the OLED display. The control software was written in C using the Arduino IDE.

A Micro OLED display (SparkFun.com) provides a 64 × 48 pixel screen, measuring approximately 0.66" in width. While compact, it is well suited for displaying temperature and timing information clearly.

Thermocouples require accurate amplification and cold-junction compensation to produce reliable readings. The MAX31855K thermocouple amplifier (Adafruit.com) fulfills this role effectively, interfacing a K-type thermocouple to the processor. It supports temperature measurements up to 1350°C with 0.25°C resolution. The amplifier is located at the probe connection and is shown wrapped in blue heat-shrink tubing.

The unit is powered by a compact 450 mAh, 3-cell LiPo battery (HobbyKing.com), providing a lightweight and portable power source.

It is remarkable how inexpensive and readily available these easy-to-use electronic components have become. Their accessibility makes it extremely easy to develop creative, custom-built solutions for a wide range of home built projects.