Staircase lighting fixtures. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Automatic stair lighting. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Lighting

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It is known that a huge amount of electricity is spent on night lighting of the entrances of residential buildings, and most of the time the light burns in vain. To avoid unnecessary energy costs, it is necessary to equip the entrances of houses with automatic machines that turn on the light for a short time only when it is needed. Below are diagrams of two options for stair lighting machines.

The scheme of the first of them is shown in fig. 1. Assume that power is supplied to the device, and capacitor C2 is discharged. Zener diode VD2 and composite transistor VT1VT2 are closed at this time; a positive voltage is applied to the base of the transistor VT3 through the resistor R3, which opens this transistor. A current flows in the circuit of the control electrode of the trinistor VS1, the trinistor is open and the lighting lamps are lit on the floors (they are marked EL1 in the diagram). As the capacitor C2 is charged through the resistor R2, the voltage across its plates increases. When it reaches the stabilization voltage of the zener diode VD2, the latter opens, then the transistors VT1, VT2 open, and the transistor VT3 closes. The trinistor VS1 also closes and the lighting lamps EL1 go out. The device is in this state most of the time, consuming a current of about 2 mA from the network. To turn on the lighting, press the SB1 button.

(click to enlarge)

All elements of the device, including lighting lamps, are powered by a rectified voltage taken from the VD3-VD6 diode bridge. The voltage required for the operation of the transistor switch and for charging the capacitor C2 (about 12 V) is obtained at the output of the parametric stabilizer VD 1 R4. Capacitor C1 smooths out voltage ripples. Resistor R1 limits the discharge current of capacitor C2 when the button SB1 is pressed. In addition, the presence of this resistor increases electrical safety when using the device in the event of a violation of the insulation of the SB1 button.

Applying voltage to the control electrode of the trinistor VS1 from its anode (through the open transistor VT3) ensures the flow of current in the control electrode circuit only until the trinistor is turned on, i.e., for fractions of a millisecond at the beginning of each half-cycle. As a result, very little power is dissipated on the VT3 transistor.

The neon lamp HL1 is installed next to the SB1 button so that it can be easily found in the dark. The same buttons are installed on the stairwells of the floors and connected in parallel. The neon lamps corresponding to them are connected to the network through 200 kΩ resistors (R6 in the diagram).

The maximum total power of lighting lamps that can be controlled by the stair lighting machine is 2 kW. SCR VS1 must be mounted on a heatsink with a cooling surface of about 300 cm², diodes VD3-VD6 - on four radiators with an area of 70 cm² each. If the load power does not exceed 300 W, it is not necessary to install the trinistor and diodes on radiators.

(click to enlarge)

On fig. 2 shows a diagram of the second version of the staircase lighting machine, which uses the K176LA7 chip. The voltage from the capacitor C2 is fed to the inputs of the logic element DD1.1. As long as the voltage across the capacitor is less than the switching threshold voltage of this element, at its output there is a high level voltage, which opens the transistor VT1. This opens the trinistor VS1 and energizes the lighting lamps EL1. With further charging of the capacitor C2, the logic element DD1.1 switches, a low-level voltage appears at its output, the transistor VT1 and the trinistor VS1 close and the lamps go out.

Publication: cxem.net

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