The switch of garlands with smooth inclusion. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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The switch of garlands with smooth inclusion. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Color and music installations, garlands

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The principle of operation of the device is based on the interaction of two voltages close in frequency - an electric lighting network (50 Hz) and pulses received from a multivibrator to control transistor switches in the power circuits of garlands.

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The luminous flux and brightness of the lamps change with a frequency equal to the frequency difference of these electrical signals. The moments of smooth ignition and extinction of the lamps in the garlands are shifted in time relative to each other, the interval between successive ignitions and extinctions of the lamps can be smoothly adjusted over a wide range - up to 10 s or more. The control pulses are generated by a three-phase multivibrator (transistors V1-V6), powered by a full-wave rectifier (diodes V12-V15). The rectified voltage is stabilized by the zener diode V7. Pulses from the multivibrator are fed to power transistor switches V8, V9, V10, in the collector circuits of which garlands of HI-H2 lamps are included. Alternately, for 1/3 of the period of the control pulses, the groups of transistors V1, V2 and V8, V3, V4 and V9, V5, V6 and V10 switch from open to closed. The variable resistor R10 sets the desired repetition rate of the control pulses. For reliable start of the multivibrator, the S1 Start button is introduced.

Incandescent lamps in garlands are connected in parallel or in series, depending on their rated voltage and filament current. Power circuits consisting of V8-V10 transistor switches and their loads - garlands are fed with pulsating voltage from a V11 diode rectifier. The current flows through the garland lamps only when the supply voltages of the power circuits and the control current pulses in the base circuits of the transistors V8, V9, V10 coincide. Due to the difference in their frequencies, there is a shift in time of the moments of ignition and extinction of the lamps and a smooth change in the brightness of their glow.

The desired frequency of ignition and extinction of the garlands is set by a variable resistor R10 of the control device. If the pulsation frequency of the light flux is greater than required, resistors R5 *, R7 * and R9 * are selected.

The power supply used a transformer TA 163-127 / 220-50 (power 86 W), made on the magnetic circuit ShL20 X 40. According to the passport data in the nominal load mode, the voltage of the windings 11-12 and 13-14 at a current of 0,68 A 15-16 and 17-18 at a current of 0,71 A are 28 V, and windings 19-20 and 21-22 at a current of 0,71 A - 6 V. Each of the garlands is made up of 10 lamps MH30-0,1 (on voltage 30 V and current 0,1 A). P210B transistors and D232 diodes work without heat sinks.

P210B transistors can be replaced with those close to them in terms of the maximum collector current, the voltage between the collector and the base, the reverse collector current and the static current transfer coefficient of the base. The allowable voltage between the emitter and the base of transistors V2, V4 and V6 of the control device must be at least 10 V.

Using silicon transistors in the power circuit, the resistor R17 can be eliminated, while the resistances of the resistors R15, R16, R18 can be twice as large.

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