The WatchDuck is an accelerometer-based low cost wireless pool alarm. It will give an alert when a child or an object fell into water. All operation in this project is controlled by PIC 18F23K20 microcontroller. The alarm is composed of two parts: the detector and the base station. The detector is using an accelerometer module (H48 from Parallax) and mounted into a bath ducky. The accelerometer measures the vertical acceleration (Z-axis) – the floating duck is following the surface waves of the pool.
When an object – a child – fell into the water, it creates waves which are detected by the accelerometer. When the G-force detected is above a threshold, the detector is sending an alert to the base station which triggers an alarm. When the G-force is bellow this threshold, the detector is periodically reporting its status to the base station (about 1 time every 2 seconds). By doing so, the base station is checking the reliability of the link with the detector and this latter, using the Power-Down functionality of the transmitter, is saving every 2 seconds. All these operation are done by a low power consumption PIC18F23K20 MCU.
The 2nd part of the alarm is the base station, which includes PIC 18F23K20 as main controller, a second RF Transceiver and provides a user interface based on a 2×20 characters LCD display and 4 touch keys. By reading and processing the messages send by the detector, this base station is able to display the detector status, the alarm status and the signal strength. The user can easily navigate through these data using the touch keys which provide a visual and acoustic feedback. When an alert is sent by the detector, the base station is triggering an alarm through a buzzer. This pool alarm is designed by Laurent Goudet.