The MAXQ3210 is a high-performance, low-power 16-bit RISC microcontroller ideally suited to environmental monitoring and alarm systems. Its internal 5V to 9V voltage regulator, wake-up timer, stop mode, and ring oscillator allow very low-power operation. The integrated analog comparator, piezoelectric horn driver, and precision voltage reference minimize component count. This application note describes how the MAXQ3210 can be use to build a system that detects water and then sounds an alarm. The complete assembly language application software is provided.