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Owners of private houses, when landscaping the site, are concerned about the question of how to automatically turn on the light at dusk and turn it off at dawn. There are two devices for this – a photorelay and an astrotimer. The first device is simpler and cheaper, the second is more complicated and more expensive. Let’s talk in more detail about the photo relay for street lighting.
Design and function
This device has many names. The most common is a photorelay, but they are also called a photocell, a light and twilight sensor, a photosensor, a photosensor, a twilight or light-control switch, a light sensor or day-night. In general, there are many names, but the essence of this does not change – the device allows you to automatically turn on the light at dusk and turn it off at dawn.
The operation of the device is based on the ability of some elements to change their parameters under the influence of sunlight. The most commonly used photoresistors, phototransistors and photodiodes. In the evening, when the illumination decreases, the parameters of the photosensitive elements begin to change. When the change reaches a certain value, the relay contacts close, supplying power to the connected load. At dawn, the changes go in the opposite direction, the contacts open, the light goes out.
Characteristics and selection
First of all, choose the voltage with which the light sensor will work: 220 V or 12 V. The next parameter is the protection class. Since the device is installed outdoors, it must be at least IP44 (numbers may be higher, lower – undesirable). This means that objects larger than 1 mm cannot get inside the device, and that it is not afraid of water splashes. The second thing you should pay attention to is the temperature regime of operation. Look for options that marginally cover the averages in your region in both positive and negative temperatures.
It is also necessary to select a photorelay model according to the power of the lamps connected to it (output power) and the load current. It, of course, can “pull” the load a little more, but there may be problems. So it is better to take even with some margin. These were the mandatory parameters by which it is necessary to choose a photorelay for street lighting. There are a few more extras.
In some models, it is possible to adjust the response threshold – to make the photosensor more or less sensitive. Decrease the sensitivity when it snows. In this case, the light reflected from the snow can be perceived as dawn. As a result, the light will turn on and off. You won’t like this show.
Pay attention to the sensitivity adjustment limits. They can be more or less. For example, for a Belarusian-made AWZ-30 photo relay, this parameter is 2-100 Lx, for a P02 photocell, the adjustment range is 10-100 Lx.
Response delay. What is the delay for? To eliminate false on / off light. For example, at night, the headlights of a passing car hit the photo relay. If the response delay is short, the light will turn off. If it is sufficient – at least 5-10 seconds, then this will not happen.
Choosing an installation site
For the correct operation of the photorelay, it is important to choose its location correctly. Several factors must be taken into account:
- Sunlight should fall on it, that is, it should be in the open air.
- The closest sources of artificial light (windows, lamps, lanterns, etc.) should be as far away as possible.
- It is not desirable that headlights fall on it.
- It is advisable to place it not very high – for ease of maintenance (it is necessary to periodically wipe the surface from dust and brush off the snow).
In order for light-sensitive automata to work correctly, you need to choose the right location
As you can see, when organizing automatic lighting on the street, choosing a place to install a photorelay is not an easy task. Sometimes you have to move it several times until you find an acceptable position. Often, if a light sensor is used to turn on a lamp on a pole, they try to place a photo relay in the same place. This is completely optional and very inconvenient – you have to clean off dust or snow quite often and climbing a pole every time is not very fun. The photorelay itself can be placed on the wall of the house, for example, and the power cable can be pulled to the lamp. This is the most convenient option.
Connection diagrams
The connection diagram for a photorelay for street lighting is simple: a phase and zero are connected to the input of the device, from the output the phase is supplied to the load (lanterns), and zero (minus) to the load comes from the machine or from the bus.
If you do everything according to the rules, the wire connection must be done in the junction box (junction box). Choose a sealed model for outdoor location, mount in an accessible place. How to connect a photorelay to outdoor lighting in this case is in the diagram below.
If you need to turn on / off a powerful lamp on a pole, in the design of which there is a choke, it is better to add a starter (contactor) to the circuit. It is designed for frequent on and off, normally tolerates inrush currents.
If the light should be turned on only for the duration of the person’s stay (in the street toilet, near the gate), a motion sensor is added to the photo relay. In such a bundle, it is better to first put a light-sensitive switch, and after it – a motion sensor. With this construction, the motion sensor will only work in the dark.
As you can see, the schemes are simple, it is quite possible to do it yourself.
Features of connecting wires
The photorelay of any manufacturer has three wires. One is red, another is blue (may be dark green) and the third can be any color but is usually black or brown. When connecting, remember:
- the red wire always goes to the lamps:
- zero (neutral) from the supply cable is connected to blue (green);
- phase is applied to black or brown.
If you look at all the above diagrams, you will see that they are drawn in compliance with these rules. That’s it, no more complications. By connecting the wires like this (do not forget that the neutral wire must also be connected to the lamp), you will get a working circuit.
How to set up a photo relay for street lighting
It is necessary to configure the light sensor after installation and connection to the network. There is a small plastic rotary dial in the lower part of the case to adjust the operation limits. Its rotation sets the sensitivity.
A little higher on the case there are arrows that indicate which way to turn to increase and decrease the sensitivity of the photorelay (left – decrease, right – increase).
To begin with, set the lowest sensitivity – drive the regulator to the extreme right position. In the evening, when the illumination is such that you decide that you should already turn on the light, start the adjustment. It is necessary to smoothly turn the knob to the left until the light turns on. On this we can assume that the setting of the photo relay for street lighting is completed.
Astrotimer
An astronomical timer (astrotimer) is another way to automate street lighting. The principle of its operation is different from the photorelay, but it also turns on the light in the evening and turns it off in the morning. Street lighting is controlled by time. This device contains data about what time it gets dark / dawn in each region in each season / day. When setting up the astrotimer, the GPS coordinates of its installation are entered, the date and current time are set. According to the programmed program, the device works.
How is it more convenient?
- It does not depend on the weather. In the case of installing a photorelay, there is a high probability of a false alarm – in cloudy weather, the light may turn on in the early evening. When light hits the photo relay, it can turn off the light in the middle of the night.
- You can install the astrotimer in the house, in the shield, anywhere. He doesn’t need light.
- It is possible to shift the on / off time by 120-240 minutes (depending on the model) relative to the set time. That is, you yourself can set the time as you like.
The disadvantage is the high price. In any case, the models that are in the distribution network are quite solid money. But you can buy in China much cheaper, however, how it will work is a question.