Remote control for light switches 1

EE July/August 1986 34 We all sometimes wish that some of the switches around the home were just a little easier to locate and operate, notably so in the dark and with less frequently used light switches, such as those for the cellar or garage light. For the physically handicapped, some switch locations present a real hindrance to their mobility in the home; for them, it would be very convenient to be able to operate the switch from a distance. The proposed wireless control system differs from, say, art IR-based set-up in that it requires no line-of- sight path between transmitter and relevant receiver, while the prac- ticable operating range is of the order of a few metres. The circuit diagram of the control transmitter shows an oscillator com- posed of Tt, T3 and T2, the latter tran- sistor merely functioning as a switching device. The oscillator fre- quency is set at about 30 kHz by means of C5 , C6 and Li: the latter con- sists of about 200 turns of 36 SWG (0 0.2 mm) enamelled...