Energy saving photo relay. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Lighting

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One of the reasons for the excessive consumption of electricity is the aimless burning of lamps in the morning and afternoon, when there is enough natural light. The reason for this is that with a slow increase in illumination, a person cannot timely determine the moment when it is time to turn off the artificial light. This situation is especially common in institutions. The authors propose a photorelay that turns off the lighting automatically and, in their opinion, devoid of many shortcomings of previous developments.

Energy waste is difficult to quantify. If we assume that the artificial light is turned off 30 minutes after the moment of sufficient natural illumination, and the lighting system consists of 20 LB-40 lamps, which approximately corresponds to a normal work or training room, then about 144 kWh of electricity will be overused per year. In fact, the light is often not turned off until the evening, so this assessment can be considered optimistic, the overspending is much greater.

To prevent overspending, automatic lighting control systems are usually used. Sophisticated centralized systems of this kind are often not available due to their high cost and complexity of installation. Those that turn on and off the lighting at a given time of day, regardless of the actual illumination, require, as a rule, systematic maintenance - adjustment of the trigger points. Devices based on presence sensors are sensitive to interference, in addition, they work only if people constantly move around the room or create sufficiently loud acoustic noise. Traditional photorelays turn on the lighting again at dusk, when in most cases it is no longer necessary.

The proposed photo relay automatically turns off the electric light when there is enough natural light, and does not turn it on in the evening, even if the switch is left on. With all this, the device allows you to turn on the light manually, if necessary. The photorelay does not require the installation of additional controls, it is quite easily integrated into the existing electrical wiring, and can, in principle, control lamps of any power. The threshold level of illumination to which it responds is adjusted when it is installed.

Rice. 1 (click to enlarge)

The scheme of the photorelay is shown in fig. 1. An alternating mains voltage of 220 V is supplied to it through a standard light switch that is not shown in the diagram and is available in the wiring. The power unit is made according to the classical scheme with a ballast capacitor C5. Resistor R5 limits the amplitude of the charging current pulse of capacitor C5 at the moment of switching on. After turning off the mains voltage, this capacitor is discharged through the resistor R7.

A half-wave rectifier is assembled on the VD6 diode, and the VD5 diode passes. through itself half-cycles of reverse polarity for VD6. This prevents the capacitor C5 from being charged by the DC component of the rectified current. After smoothing the ripples by the capacitor C7, the rectified voltage is supplied to the stabilizer with an inductance of 100 ... 200 μH, it must be designed for the total current of the lamps switched by the photorelay.

Since the switching on and off of the triac occurs at zero values ​​of the mains voltage, in most cases the inductor can be replaced with a jumper. It is needed only if there are complaints about the interference created by the photo relay. With a total lamp power of more than 150 W, the triac VS1 should be installed on a heat sink of sufficient area. The AL307BM LED can be replaced with any other, preferably with increased brightness.

Fig. 2

The photodiode used by the authors was not marked. Almost any of them can work in this device, you just need to choose the value of the resistor R1. It should be noted that the correct operation of the photorelay largely depends on the place and method of installing the photodiode. It is difficult to indicate any clear criteria for choosing this place due to the wide variety of room geometry, the nature of their natural lighting, the configuration, placement and power of artificial light sources. Therefore, the installation site will have to be selected empirically according to the most confident operation of the photorelay at the right time. To eliminate the influence of interference, the LED should be connected to the board with wires of minimum length twisted together. Note that it is galvanically connected to the mains.

The photorelay microcontroller program is written in PIC Basic Pro. The computer program IC-Prog was used to load the program into the microcontroller. Since information about the required configuration of the microcontroller is available in the HEX-file of the program (this is one of the differences between PIC microcontrollers and AVR), the programmer installs it automatically.

A photorelay assembled from serviceable parts, as a rule, starts working immediately after being turned on. In order to set the illumination threshold, above which the electric lighting must be turned off, it is necessary to ensure that the illumination in the room becomes equal to this value (for example, wait for the appropriate time of day). By closing the contacts of the SA1 switch, you should set the trimmer resistor R2 to a position as close as possible to the one at which the HL1 LED turns on and off when passing through.

If during the operation of the device it is necessary to turn on the lighting that turned off the photo relay, it is enough to briefly open and immediately close the switch in the circuit of its mains supply.

The microcontroller program can be downloaded from ftp://ftp.radio.ru/pub/2013/05/1.zip.

Literature

1. Aizenberg Yu. B. (ed.) Energy saving in lighting. - M.: Sign, 1999.
2. Werner V. Intelligent control system for interior lighting. - Light engineering, 1993, No. 4, p. 15-19.

Author: B. Poezzhalov, Y. Martynyuk

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