Automatic lighting switch in utility rooms. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Automatic lighting switch in utility rooms. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Lighting

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The author of the published article tried a large number of circuit breakers in utility rooms and opted for a design that has been serving him for more than ten years. The device developed by him, in addition to a simple circuit design, differs from those already known to our readers in that it is in a de-energized state when the door of the room is closed and the lighting is turned off.

The schematic diagram of the device is shown in fig. one.

Automatic lighting switch in utility rooms

The SB1 pushbutton switch is located on the jamb above the door. The door handle located inside the room is made of conductive material and is connected by a wire to the output of the resistor R1. The position of the SB1 switch contacts shown in the diagram corresponds to the open door. In this case, through the closed contacts SB1.1, the supply voltage is supplied to both the device and the lighting lamp. Transistors VT1. VT2 is closed, and relay K1 is de-energized.

When the door is closed from the outside of the room, the SB1.1 switch contacts break the power circuit before the SB1.2 contacts close, as a result, the lighting lamp goes out and the device is de-energized.

When the door is closed from inside the room, the alternating voltage induced on the human body, at the moment the inner handle is touched, through the resistor R1 and the capacitor C1, enters the base of the transistor VT1, which opens, and a voltage appears on the resistor R2, which opens the transistor VT2. Relay K1 is activated, its contacts K1.1 block the contacts of the switch (SB 1).

When the door is fully closed, the contacts SB1.1 open, the contacts SB1.2 close, keeping the transistor VT2 in the open state and after releasing the door handle.

The details of the circuit breaker are placed on a printed circuit board 40x50 mm in size, made of one-sided foil fiberglass 1 mm thick (Fig. 2).

Automatic lighting switch in utility rooms

The board is placed in a plastic box fixed above the door. Resistors MLT-0,125, capacitors KM-6 (C2), K50-6 (C3) and K73-17 (C 1) for an operating voltage of 630 V and C4 for 250 V were used. Instead of VT1, any low-power transistor of the corresponding structures with a base current transfer coefficient of 150 ... 200, and in place of the transistor VT2 - any transistor of the same series with a base current transfer coefficient of at least 450 ... 500.

We will replace the KD906A (VD2) diode bridge with KD906B, KD906V diodes or with a small-sized diode bridge of another series (KTs407A, for example). You can also make a bridge from diodes of the KD102, KD103, KD522 and other series, but this will require a change in the design of the printed circuit board. Instead of the D814B zener diode, the KS510A is suitable.

Electromagnetic relay K1 - RES-10, passport RS4.524.308, RS4.524.311 or RS4.524.321. If the capacitance of the capacitor

Increase C4 from 0.47 to 0,68 uF, and use the KS1A zener diode as VD512, then the RES-10 relay with passports RS524 303, RS4.524.312, RS4 524.322 is also suitable.

As SB1, the widely used push-button switch EI721000 is used. In its absence, you can use any push-button switch suitable for the switched voltage and current (for example, KM2-1). The only replacement condition is that when the door is closed, the opening of contacts SB1.1 must occur before the closing of contacts SB1.2.

The door handle is connected to the device with two twisted wires, it is advisable to use wires from the handset. One conductor connects the handle to resistor R1, the second is connected to the negative terminal C3. A loop is made at the transition point of the wire from the door to the jamb.

When establishing a circuit breaker, care should be taken, since its power supply is made according to a transformerless circuit. First, even before connecting the SB1 switch, turn on the device in the network and, touching the output of the board intended for connection with the door handle, check whether the K1 relay is activated. Then, having put the switch in place, connect it to the door handle and switch SB1 and make sure that when the door is open, relay K1 is activated only when a person touches the door handle with his hand. If this does not happen, it is necessary to select the capacitance of the capacitor C1. It is desirable that its value be as low as possible. Next, close the door from the outside. At the same time, the lighting lamp should go out. If it continues to burn, you need to reduce the capacitance of the capacitor C3.

In conclusion, the operation of the device is checked when the door of the room is closed from the inside.

It remains to be added that the inner door handle can also be made of insulating material, but in this case, a plate of copper foil must be glued to its back surface, to which the wire leading to the circuit breaker must be soldered.

All circuits of the device are galvanically connected to the network, therefore, during assembly and operation, it is necessary to exclude the possibility of touching its elements, except for the left resistor R1 according to the output circuit. Carefully insulate the end of the "shielding" wire twisted with the wire to the handle. To limit the inrush current when turned on in series with any of the outputs of the VD2 diode bridge, it is advisable to install a 43 ... 56 Ohm 0,5 W resistor.

Author: K. Kupriyanov, St. Petersburg

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