Frequent bed-wetting can be a real problem for many children. Occasional bed wetting by toddlers and young children is normal and can be tolerated but it can be a problem when it becomes a regular occurrence. Ultimately, it is in the best interest of the child to learn how to have a dry night’s sleep without the unpleasantness of waking up saturated and needing to have all the bedclothes changed. From the parents’ perspective, there is the constant work of extra washing of sheets, pyjamas and bedding after each bed-wetting incident has occurred.

Commercial bed-wetting alarms are available but typically they involve the use of an aluminium foil under-sheet. They do work but the child and bedding still ends up being wringing wet and you still have to go through the process of changing wet bedclothes in the middle of the night. This is the big advantage of our new Bed-Wetting Alert. It detects the immediate presence of wetness in the child’s nappy and sounds the alarm to awaken the child who can then toddle off to the toilet. If not, the alarm will continue to sound at a much lower level, indicating to the parent there has been an alert condition which requires attention.

Fig.1: this is the modified transmitter. It uses MOSFET Q4 to turn it on in response to low resistance (moisture) across the sensor inputs.