Automatic switching on of light. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Automatic switching on of light. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Lighting

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The proposed device can be used for utility rooms in the apartment (in the bathroom, toilet, pantry, etc.). Opening and then closing the door turns on the light, and the next opening and closing turns it off. To do this, a reed switch must be installed on the door jamb. and on the door itself there is a permanent magnet that keeps the reed switch closed. when the door is closed. The easiest way for this purpose is to use a pair of magnet / reed switch from the available 8 sale of security alarm devices.

Automatic light on

If the door is closed, a high level (logical T) is applied to the clock input C of the lower trigger through the closed reed switch K. If the door opens and then closes again, there is a change of levels "1" - "0" - "1". The D-flip-flop is triggered by the "0" - "1" difference, and in response to the increase in the level, it "overturns". with each difference "0" - "G at the input C, it changes its state to the opposite.

After switching the trigger, a high level from its output opens the thyristor Ti through the transistor T. which switches lamp I. The thyristor opens at the beginning of each half-cycle of the mains voltage, while the trigger output is maintained high. A pulsating (rectified) mains voltage is supplied to the lamp through a diode bridge on diodes D2 ... 05. The subsequent opening and closing of the door resets the trigger, its output goes low, and the lamp goes out.

The IC is powered by a parametric stabilizer on the zener diode D1, the operating current for which is set by resistors R4 R6. Capacitor C2 eliminates power supply interference, and C1 - voltage surges when the reed switch is triggered.

The device can be assembled by surface mounting on a piece of fiberglass or getinaks and placed in a suitable plastic box, which is fixed somewhere on the door jamb or near the lamp so that it is not conspicuous.

Since the circuit is powered by a transformerless circuit, care should be taken during commissioning. It is best to debug the logical part (before the transistor) separately. powered from a constant voltage source of 7.. 10 V (possible from several batteries) The source terminals are connected to the capacitor C2, and the zener diode D1 is temporarily disconnected. Having achieved reliable triggering when opening and closing the door, you can connect the power section.

Chip 4013 can be replaced by domestic K561TM2. a high-voltage transistor is required with a permissible operating voltage of at least 300 V. for example. KT812. KT826. KT940A. Diodes D2 ... D5 - KD202N, R Thyristor can be taken KU202ZH.

As a zener diode, any of the D814, KC175 ... KC1Q1 series are suitable.

Literature

Hobby Elektronika, 70/99

Author: A.Belsky

See other articles Section Lighting.

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