This processor-driven automatic fan controller does not just run in parallel with the toilet light, but instead allows the user to adjust the running time of the fan using a single-button system. The selected time can be read from a single-digit display. The fan can also be stopped early using the same button.Most toilet fans are switched on and off along with the toilet light, and some continue to run for a certain amount of time after the light is switched off. Since the need for fresh air is closely related to the particular reason for visiting the toilet, the author of this article wanted to have a bit more influence over how long the fan continued to run. The nicest solution would be to have a fan whose running time could be entirely chosen by the user. Naturally, switching the fan off early should also be possible, and it would be a useful extra feature to have the operating time of the fan shown on a display.