Swith For diagram

In most WCs with an extractor the fan is hooked up to the lighting circuit and that is swaped on and off either in sympathy with the light or with a brief prolong. Since rest rooms are every so often used for laundry the fingers or simply for a fast seem within the reflect, it is no lengthyer at all times necessary to alter the air within the smallest room in the house. The following circuit robotically determines whether there truly is any want to run the fan and reacts appropriately. No odour sensor is needed: we just appoint a small contact that observes when and for a way lengthy the bathroom seat lid is lifted.

If the seat lid is left up for no much less than some presettable minimum time t1, the fan is set working for another presettable time t2. In the instance shown the contact is made using a small magnet on the lid and a reed change established on the cistern. The leisure is straightforward: IC2, the acquainted 555, forms a timer whose period can also be adjusted up to roughly 10 to 12 minutes using P2. This resolves the fan running time. There are three CMOS NAND gates (type 4093) between the reed switch and the timer enter which generate the desired set off signal. When the lid is within the ‘up’ place the reed swap is closed.

Capacitor C1 costs via P1 unless it reaches the level the place the output of IC1a switches from good judgment 1 to logic 0. The output of IC1b then goes to logic 1. The fringe of the zero-1 transition, handed during the RC community fashioned with the aid of C2 and R2, leads to the output of IC1c going to common sense zero for a 2d. This is taken to the set off enter on pin 2 of timer IC2, which in turn changees on the relay which lead tos the fan to run for the time frame decided by using P2. The circuit is powered from a small transformer with a secondary winding turning in between approximately eight V and 10 V. Do no longer omit to incorporate an acceptable fuse on the main facet.

The circuit round IC1b and IC1c ensure thats that the fan does no lengthyer run continuously if the bathroom seat lid is left up for a protracted length. The time constant of P1 and C1 is set so that the fan does no lengthyer run as a result of lavatorial transactions of a extra minor nature, the place the lid is opened and then closed quickly afterwards, before C1 has a possibility to cost sufficiently to trigger the circuit.