A simple photorelay. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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Using a modern element base, it is possible to build a relatively simple photorelay that will automatically smoothly turn on the lighting when it gets dark and turn it off smoothly at dawn.

Such a machine can be installed in the entrance, utility rooms of a rural estate, or used to control street lamps located, for example, in the courtyard of your house or along the perimeter of a garden plot.

The "main" part of the device (Fig. 1) is the KR1182PM1 microcircuit, which is a phase power regulator.

Detailed information about it can be found in the article by A. Nemich "Chip KR1182PM1 - phase power regulator"in "Radio", 1999, No. 7, pp. 44 - 46. The photo relay works like this. During daylight hours, the phototransistor VT1 is illuminated, the current through its junction flows such that the voltage at pins 6 and 3 of the DA1 chip is small. Transistor analogs of trinistors the microcircuits are closed, the triac VS1 is closed, the incandescent lamp EL1 is not lit.When darkness falls, the current through the phototransistor decreases significantly, and the voltage at the control terminals 6 and 3 increases.

Since the device does not contain threshold elements, at the onset of darkness and dawn, the lamp lights up and goes out gradually. The sensitivity of the device to light is very high, as a result, the lamp is lit at full power in the late twilight, when it is really needed.

The used microcircuit is capable of operating without an external triac with a load of up to 150 watts. But incandescent lamps have one bad "habit" - they suddenly burn out not only when turned on, but also during operation. And this can be accompanied by a current pulse reaching tens of amperes. Such a current inevitably leads to damage to the microcircuit.

If it is easy enough to protect the lamp from burning out at the time of power-up, then it is impossible to predict its behavior during operation. To avoid unnecessary damage to the microcircuit, it is advisable to install a triac if a lamp with a power of more than 40 W is used.

Capacitor C1 is designed for smooth ignition of the lamp when the power supply to the device is supplied at night. Resistor R1 quickly discharges capacitor C1 when, with an unlit phototransistor, the mains voltage can be turned off and on. Inductor L1 and capacitor C4 reduce the interference that occurs during operation of the device.

The "pinout" of the phototransistor indicated in the diagram is shown in fig. 2. It can be replaced with L-36P3C, and the triac - with KU208D1, TS112-10-4, TS112-16-4, TS122-25-6 and others similar for a voltage of at least 400 V and the corresponding load current. If necessary, it is installed on a heat sink. For example, with a KU208G triac, incandescent lamps with a total power of up to 1000 W can be used as a load, while the triac is installed on a heat sink with a surface area of ​​at least 300 cm2.

Capacitor C4 - K73-16, K73-17, K78-2 for a voltage of at least 400 V, the remaining capacitors - K50-35, K53-4 or imported analogues.

The inductor is wound with PEV-2 0,82 wire (60 turns) on two glued (for example, with BF-2 glue) K38x24x7 rings made of M2000NM ferrite. But the previously sharp edges of the ferrite are blunted, and then the folded rings are wrapped with braid or fluoroplastic tape. The wire is laid with "tightness", in one layer. The finished throttle is impregnated with varnish, which reduces its buzzing. When the machine is operating with a load of less than 300 W, it is permissible to use a magnetic core of smaller dimensions.

To protect the microcircuit and the triac from voltage surges, a varistor for a voltage of 4 ... 420 V can be connected in parallel with the capacitor C470.

A properly installed device does not need to be adjusted. The phototransistor is installed so that it does not receive light from incandescent lamps. If you need to increase the sensitivity, you should use a second phototransistor connected in parallel with the first.

When installing the device outdoors, choose a dark place for it, for example, on the north side of a lamppost. The body of the device is painted with light paint, it must be spacious enough and not have ventilation holes, otherwise, with the onset of autumn cold weather, it can become a haven for insects.

In case of installation of the photorelay outdoors, it is necessary to use connecting cords and wires intended for outdoor wiring, for example, ShRT, ShPS. In special cases, it is necessary to take into account the possibility of damage to the wires by rodents, so it is better to use a wire in a metal braid - types PRF, PRFL, PRN.

Author: A.Butov, Kurba village, Yaroslavl region.

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