Here is an ultra-simple device to demonstrate in exhibitions and science fairs, but which can also be used to detect moisture and leaks at home. It can also be used to indicate the beginning of rain. Scrap components can be used.
You put a sensor outside your home and plug it into the outlet. When the first raindrops begin to fall or there are still flood and leaks, the bulb lights up. The handset is very simple as there is only one component. Even the sensor is improvised with wire and cloth.
The detector works by conducting the current through the fabric between two wire screens when it is moistened. The current is enough to light a small incandescent bulb.
But be careful, the device is not isolated from the power supply and should be installed and handled with care as it may cause dangerous shocks to the operator.
In Figure 1, we have the diagram of the device and its assembly.
The sensor is formed by two 10 x 10 cm wire screens having between them a piece of dry cloth with some salt. The bulb should be 5-15 W incandescent. Do not use another type of bulb.
