Wiring diagram for photorelay for street lighting

At nightfall, street lights are lit along the roads. Previously, they were turned on and off by utility workers. Now the operation of the lamps is controlled by an electronic device – a photorelay. Lighting automation is especially convenient in remote areas where maintenance personnel have a long commute. You can use a photorelay for street lighting not only for utilities, but also for owners of their own plots. We will now try to find out what this device is.

What does the photo relay consist of, and the principle of its operation

This device has a lot of names: photosensor, photosensor, photocell, etc. Whatever it is called, the essence remains the same. The device of the photorelay is very simple. Inside the device case there is an electronic board with a set of radio components. The soldered circuit of the photorelay forms an electronic key, which is based on a photosensitive element. This can be a photoresistor, photodiode, etc. Additional circuit elements prevent erroneous operation of the sensor, help to make fine adjustments, and are responsible for other useful functions.

The work of the photorelay can be seen by the photoresistor. This part has its own resistance that prevents the passage of current. With the onset of darkness, the resistance of the photoresistor decreases. The current passes freely, which leads to the operation of the electronic key. This leads to a short circuit of the contacts of the device to which the lighting devices are connected. With the onset of dawn, all actions go in reverse order. Increasing the resistance of the photoresistor prevents the flow of current. The electronic key opens the contacts and the street lighting turns off.

Can’t you do without a photorelay at home?

An illiterate question about the need to use a photorelay can be asked by a person who does not care about the convenience of his home and the arrangement of the adjacent territory. The work of the device is aimed not only at creating beautiful light accents. The photorelay is used for the convenience of lighting control, as well as energy savings.

Let’s look at a few arguments in favor of the device:

• Let’s start with convenience. The lighting system is controlled by a switch. It is usually placed at the door near the room. Indoors is fine. And take, for example, your yard. To turn on the light you have to get through the darkness to the switch. And if the barn is located in the far yard? A long journey begins in the dark with a flashlight. The photo sensor will allow you to adjust the illumination of frequently visited places, which will save the owner from wandering in the dark.
• Now about saving. Owners of large private plots install many lighting fixtures to illuminate the garage, recreation area, entrance to the house and other places. For the convenience of controlling the entire system, you can use one switch, but what will be the power consumption. The light will burn even in unnecessary places. And in the morning after a stormy rest, it’s too lazy to get up early to turn off the lighting. A device with a photo sensor will do everything by itself with the onset of dawn. And if you still use a motion sensor, in general, the lighting will turn on only where there are people.
• Photorelay – primitive, but at least some protection against theftin. The light turned on at night in the absence of the owners in the country creates an imitation of presence. Not every petty hooligan will dare to enter the yard.

If the above arguments are unconvincing, you can do without a photo relay. But is it necessary to save on your own comfort, if the device costs not so much money. Moreover, the photorelay can be connected without problems with your own hands.

The optimal location for installing a photo relay

For the lighting to work correctly, you need to choose the right location for the photocell:

• from dawn to dusk, the photo sensor should be illuminated by sunlight or located in the brightest place;
• the photocell must not be exposed to artificial lighting;
• the device is placed near the road so that the sensor is not illuminated by headlights;
• the decrease in the sensitivity of the device occurs after the contamination of the photocell, so the relay is placed at a convenient height for maintenance.

Choosing the right place for a photo relay is a difficult task. Usually this process involves moving the device around the yard until a positive result is achieved.

The main technical characteristics of the photorelay

In order for the photorelay to work properly in the lighting system, it must be correctly selected taking into account the technical characteristics. All devices have the following parameters:

• Each brand of relay is designed to work with a voltage of 12, 24 and 220 volts. For home lighting, the latter option is used. When using low-voltage devices in a 220V network, you will have to install converters. It’s expensive and doesn’t always work well.
• Amperes – the second important characteristic of the device. To calculate the maximum switching current, the sum of the power of all the lamps of the lighting system is calculated. The result obtained is divided by the mains voltage. At home, this is 220V. The figure obtained after the calculation must be less than the amperes indicated on the photo relay. Otherwise, the device will quickly fail.
• From the sensitivity of the photocell depends on the threshold for turning on and off the lighting. It is optimal to use a device with parameters of 2–100 lx or 5–100 lx.
• The delay in the operation of the photosensor prevents the lighting from turning off immediately after a short-term light from the headlights of a passing car. The optimal delay is from 5 to 7 seconds.
• Appliance power affects energy savings. Typically, during operation, consumption is up to 5 watts, and while waiting – 1 watt.
• Degree of protection indicates the place where the use of a photoelectric relay is allowed. For example, on the street it is optimal to use a device with an IP44 indicator.

In very cold or hot regions, it is important to pay attention to the allowable operating temperature range.

Varieties of advanced photo relays

The simplest photorelay reacts only to incoming light. However, it is not always necessary that the light bulbs shine all night. Manufacturers have developed advanced devices stuffed with additional sensors:

• Very handy device with a motion sensor. The lighting turns on only when a moving object, person or animal enters the sensor’s coverage area.
• The motion sensor, supplemented by a timer, allows you to set the device to operate at a certain time. The light will turn on, for example, when the owner comes home from work late, and will not blink in the middle of the night from running cats or dogs.
• The programmable device is very expensive. It even allows you to set the date and time when you want to turn on the lighting.

Among all models, photo relays with a timer and a motion sensor are considered the most popular.

The difference between the photorelay at the installation site

Manufacturers produce devices for indoor and outdoor installation. The last type of photorelay is designed for outdoor installation. The electronic circuit of the device is protected by a sealed housing that is resistant to aggressive environmental influences.

A photorelay for indoor installation is mounted outdoors in a protective housing or electrical panel inside the building. Only a remote photocell goes outside.

If at home it is decided to make controlled lighting with your own hands, it is better to give preference to outdoor-type devices.

Connection diagram examples

The simplest photo relay connection diagram for street lighting is shown in the photo. The phase wire is interrupted as it is connected to the input and output of the device. Further, the phase from the output goes to the light bulb. Zero goes with a whole wire from the electrical panel bus. It is connected to the input of the photorelay and the load.

Primitive schemes are not always convenient to use and dangerous. It is better to connect a photorelay installed on the street to the mains using a junction box, only it must also be sealed. The photo shows a diagram of how a photo relay for street lighting is connected through a junction box.

The photorelay can control the operation of lamps of any power. Many of them have built-in chokes. In order for a weak device to cope with a large load, a contactor is added to the circuit. As a result, the power of the photorelay should be enough to control the starter, and with the help of moving contacts it supplies voltage to the lighting devices.

When using a motion sensor, a different connection scheme is used. First, the current from the network is supplied to the photo relay, and from it it is already supplied to the motion sensor and the lamp. Such a scheme includes lighting when any object moves only at night.

Any of the proposed schemes is simple, and can be assembled with your own hands without any problems.

How to deal with wires

Any model of the device has three multi-colored wires. However, an inexperienced person will get confused even in them. Immediately you need to look at the color of the insulation. The red, black or brown wire is the phase. Blue or green is zero. The third wire is ground. It usually goes green with a yellow stripe.

If the device has only an output for connection, then look at the letter designation: N – zero, L – phase, PE – ground.

On the video connection of the photorelay:

Setting the sensitivity of the photo relay

Sensor adjustment is performed only after connecting the annual lighting scheme to the mains. The adjustment sets the sensor’s response limit, that is, its sensitivity to light. For these purposes, a plastic screw is installed on the back of the device. To know in which direction to turn it, look at the designation: “+” indicates an increase in the sensitivity of the photocell, and “-” indicates its decrease.

Adjustment begins by turning the screw all the way to the right. If you decide that it is in this darkness that the lights should turn on, slowly turn the knob to the left. As soon as the bulbs light up, the setting can be considered finished.

As you can see, the photo relay is a very simple device. Installing it is no more difficult than screwing in a light bulb, and a positive result will already be visible by nightfall.