Thermal conductivity is generally the tool of choice for quantification of fixed gases, particularly lighter-than-air gases. Unfortunately, gas chromatography-thermal conductivity detectors (GC-TCDs) are difficult to introduce in first- and second-year chemistry courses where the cost and number of instruments, as well as the space required, is impractical. In this article, the authors describe the development of a small, inexpensive microcontroller-based TCD for undergraduate teaching and research laboratory experiments which utilizes a matched pellistor pair to quantify hydrogen. The total cost of materials is under $200, including the microcontroller, electronics, TCD pellistor pair, and the mechanical parts which serve as the housing and analysis chamber.