Mains-based remote controller

2 mains-based remote controller 69 EE July/August 1986 A7 This combination of transmitter and receiver is based upon the use of the mains network in the home for re- mote control of mains-operated dom- estic appliances. Figure 1 shows the transmitter, which merely superimposes a 36 kHz signal on the 50 Hz mains voltage if Si is op- erated. It is noted that ICI is fed direct off the mains voltage by means of a rectifier circuit composed of Di, D2, zener diodes D3, D4, and smoothing capacitor C4; the pro- posed configuration is to supply +20 V with respect to the mains neutral (0) line. The 36 kHz output signal of the opamp is fed to the mains by means of coupling capaci- tor C3. R2 is a bleeder resistor to dis- charge CI and C2 after the circuit has been unplugged from the mains outlet. The receiver, shown in Fig. 2, is fed with an inexpensive door bell trans- former, although any other type sup- plying 6 to 8 V AC at about 300 mA should do just as well. Apart from being used to po...