This document reports details the development of a solid stool detection system. On behalf of Momo Medical - a TU Delft-based startup company - a device for detecting defecates by elderly people has been designed. The goal of the detection system is to detect solid stools by elderly patients wearing a diaper and to notify the nurses in a nursing home accordingly. The project has been organized and conducted in two groups: Hardware & Software. Our group has been in charge of the hardware. The other group has been responsible for the software. The main focus in this report will be the hardware design of the system. This report contains: the analysis of the problem, the development of a solution, the design and the evaluation of the device in test. The developed device detects methane by means of multiple gas sensors, since methane is the main gas component released while defecating. Several iterations making a suited printed circuit board and case have been carried out, while taking aspects like safety, reliability and noise performance into account. The report concludes with a summary of main results and an outline of future work.