Toilet ventilator control

1 EE July/August 1986 128toilet ventilator control 2V7 Many toilets have a ventilator, which is energized along with the toilet light. However, since not every visit of the toilet requires the ventilator to start turning, this circuit offers an im- proved control method, which is still based upon the use of the light switch. The circuit configuration shown in Fig. 1 may be used in case the toilet ventilator is powered from the same mains lines as the light. Bridge recti- fier Bi and opto-coupler Type TIL113 serve to detect whether or not the toilet light is on. The ventilator is ar- ranged to start turning after the light switch has been operated twice. If this is the case, the output of NI will go high twice; the first time, C4 is charged, the second time will cause pin 6 of N2 to be logic high, while the output of this NAND Schmitt trig- ger gate will supply a logic low pulse to N3 when the voltage at point 3 reaches the logic one level (see timing diagram Fig. 2). N3, then, cha...