The automatic switch of illumination of a landing. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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The automatic switch of illumination of a ladder platform. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Lighting

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The device, the diagram of which is shown in the figure, turns on the lighting on the landing when any of the doors leading to it is opened and turns it off after a certain period of time after the doors are closed. In the initial state, the contacts of all reed switches SF1-SFn installed on the door frames are closed under the action of permanent magnets located near them, mounted on the doors. As a result, the logic level at the output of the element DD1.2 is low. Capacitor C3 is charged to the supply voltage, so a low level is also present at the output of element DD1.4. Transistor VT1 and trinistor VS1 are closed, lighting lamp EL1 is off.

Automatic stairwell lighting switch

It is worth opening the door, the contacts of the reed switch installed on its frame will be open, and the capacitor C2 will be charged through the resistor R2. The low level at the output of the element DD1.2 will change to a high one, which will lead to the discharge of the capacitor C3 through the diode VD3, the resistor R3 and the output circuit of the element DD1.2. The level at the output of the element DD1.4, in turn, will become high, which will lead to the opening of the transistor VT1, the trinistor VS1 and the ignition of the lamp EL1.

When the door is closed and the level at the output of the element DD1.2 becomes low again, the lamp EL1 will remain on for some time until the capacitor C3 is charged through the resistor R4. With the ratings of the elements indicated in the diagram, this will take approximately 20 s, after which the device will return to its original state and the EL1 lamp will go out.

The diode bridge VD1 is necessary so that the current through the trinistor VS1 flows in only one direction. The R1C1VD2 circuit is the power node of the DD1 chip.

Instead of the K561LA7 chip, you can install K561LE5.

The conclusions of many reed switches (including KEM-1, KEM-2) are not designed for soldering. Therefore, the ends of the connecting wires stripped of insulation are simply wound on them, fixing them with pieces of a PVC tube. The permanent magnets required to control the reed switches can be extracted, for example, from magnetic door latches.

Instead of reed switches, other contact sensors can be used, for example, microswitches P1M9-1T, P1M9-2T, MP1, MP3, MP5, MP10, setting them in such a way that the contacts close when closing and open when the doors are opened.

Author: V.Polovinkin, Zheleznogorsk, Kursk region.

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