Automatic lighting switch. Scheme, description

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

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Encyclopedia of radio electronics and electrical engineering / Lighting

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Small rural settlements and horticultural associations are provided with electricity by complete transformer substations. The functions of the automatic lighting switch are performed in them by the photorelay FR-2. The operation of this device is unstable: the time to turn on and off the lighting depends markedly on the mains voltage and ambient temperature. The author of the published article has developed his own version of the machine, which he invites our readers to get acquainted with.

The automatic lighting switch (ABO) consists of a photo sensor (photoresistor), an electronic unit and a power supply. The electronic unit (see figure) includes a converter on transistors VT1, VT2, an amplifier on transistors VT3, VT4, an executive relay K1 and a device for blocking it ("anti-bounce").

Automatic lighting switch

The electronic unit is mounted on two textolite boards 105x140 mm in size, installed one above the other at a distance of 40 mm. On the top board, the switch SA1 is mounted with resistors R3 - R10 fixed on its terminals, variable resistors R11, R12, relay K1, capacitor C1 and LED HL1, and on the bottom - all other parts.

The photoresistor is placed on one of the vertical walls of the complete transformer substation (KTP). At dusk, a stream of light from the sky falls on it. It is possible to enhance the illumination of the photoresistor by installing a reflector made of stainless steel or mirror glass at an angle of 45° to the vertical wall of the PTS at such a distance from it that in winter the snow is not trapped by the reflector and does not block the access of light to the photoresistor. It will also protect the photoresistor from the direct rays of the sun, which can damage it, as well as from the headlights of cars or street lights, causing a false operation of the machine.

The AVO uses a photoresistor FSD-G1, fixed resistors MLT-2 (R21) and MLT-0,5 (the rest), variables R11 and R12 - SP3-4bM or SP-0,5. Capacitor C1 - K50-7 (option "A") with parallel connection of two sections (300 microfarad each). Switch SA1 - 10P1N, SA2 is made in the form of a jumper. The KT3107I transistor has a current gain of about 200, and KT502G - about 150.

The author used the relay MERA LUMEL (Poland). Any other voltage of 12 V is also suitable, with a winding resistance of 100 ... 140 Ohms. The power contacts of the relay must ensure the activation of the starter in the transformer substation and be rated for a current of at least 10 A.

A source with a stabilized output voltage of 14 ... 15 V is suitable as a power supply unit. The current consumed by the AVO when the relay is on (Dark mode) is 100 mA, and when it is off (Light mode) - 16 mA.

Before adjusting the air cooler, check the voltage on the electrodes of the transistors (see table). They are measured against the +15 V circuit with a high-resistance input voltmeter. Before starting measurements, the sliders of resistors R11, R12 should be set to the position corresponding to the minimum resistance. Then put the switch SA1 in position "10" and rotate the slider of the resistor R11 from the position of minimum resistance until the relay is turned on (the HL1 LED lights up). After that, you can measure the voltage at the electrodes of the transistors in the "Dark" mode, and by setting the SA1 switch to position "2", in the "Light" mode.

Table

AVO operating mode	Voltage on the electrodes of transistors, V
	VT1			VT2			VT3			VT4
	Б	К	Э	Б	К	Э	Б	К	Э	Б	К	Э
"Light"	1,65	0,92	0,90	0,92	11,47	0,90	1,26	0,64	0,59	0,64	15,17	0,59
"Dark"	1,54	1,59	0,89	1,59	0,89	0,89	0,50	4,68	3,90	4,68	3,96	3,90

To set up the air cooler at the place of its installation, it is necessary to turn off the capacitor C2 with switch SA1, set the sliders of resistors R11 and R12 to the minimum resistance position, set switch SA1 to position "1" and close the photoresistor from all sides from light. Next, you need to turn on the power and slowly turn the slider of the resistor R11 until the relay trips. When a bounce occurs, it must be eliminated by slightly turning the slider of the resistor R12. Then, by turning the slider of the resistor R11 in the direction of increasing resistance, restore the operation of the relay in the "Dark" mode.

Using switch SA1, you can evaluate the sensitivity of a photoresistor instance designed to work in ABO. To do this, by moving the movable contact of the switch from position "1" to positions "2", "3", "4", etc., we determine in which of them the air cooler is turned on. The greater the resistance turns on instead of R1, the higher the sensitivity of the photoresistor. Over time, it falls, if the air cooler starts to operate in positions "4", "3", then such a photoresistor should be replaced. In order for the AVO to work with greater illumination, the resistance of the resistor R11 should be increased. In this case, the position of the switch, at which the ABO is turned on, will also change.

Then you need to set the switch SA1 to position "2", connect the capacitor C2 with the switch SA1 and check the operation of the relay blocking device that eliminates its bounce. To do this, by moving the movable contact of the switch SA1 from position "1" ("Dark") to position "2" (Light), check the relay off delay (about 20 s).

From the "Light" mode to the "Dark" mode, the AVO switches without delay and remains in this mode for about 40 s, even if the switch is immediately returned to the "Light" mode.

In conclusion, the switch SA1 is set to position "1" and light access to the photoresistor is opened.

Author: N. Mikhailyuk, Moscow

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