Usually automatic device switch on and off the Christmas tree lights in leaps and bounds, without changing the brightness. But the electronic switch scheme is presented in figure — does not have this drawback. The basis of his work is based on the principle of beats that occur between the frequencies of the mains and generator. The latter is a multivibrator transistors T1, T2. It generates rectangular pulses with a frequency of (100 ± Δ) Hz (100 Hz is the fundamental frequency of the multivibrator, And the frequency of the beating, which switch lamp garland which is in the range of 0.1—8 Hz). Adjustment of the burning time of the lamps is variable resistor R6 “Smoothly” and R7 “Rough”.
Rectangular pulses from the collectors of T1, T2 through the capacitors C1, C4 are received to the control electrodes of the thyristors D5 and D11. They open positive differentiated pulse phase, while its negative part is damped by the diodes D7, D10.
Schematic diagram of the soft switch.
The device is powered directly from the mains through the rectifier bridge diodes D1—D4. Isolation between power circuits and control is the diode D6.
Garland, for a voltage of 220 V and current of 0.2—0.3 And are connected to the ports on SH1 and ø2.
V. VOKHMYANIN, Kirov
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