Automation of lighting supply in an apartment, in a house or on the street is achieved through the use of a photorelay. When properly configured, it will turn on the light when it gets dark and turn it off during daylight hours. Modern devices contain a setting by which you can set the response depending on the illumination. They are an integral part of the "smart home" system, which takes on a significant part of the responsibilities of the owners. The photo relay circuit, first of all, contains a resistor that changes resistance under the action of light. It is easy to assemble and customize by hand.
Operation principle
Scheme for connecting a photorelay for street lighting includes a sensor, an amplifier and an actuator. Photoconductor PR1 under the action of light changes resistance. This changes the amount of electric current passing through it. The signal is amplified by the composite transistor VT1, VT2 (Darlington circuit), and from it it goes to the actuator, which is the electromagnetic relay K1.
In the dark resistancephotocell is a few mOhm. Under the action of light, it is reduced to a few kOhm. At the same time, transistors VT1, VT2 open, turning on relay K1, which controls the load circuit through contact K1.1. Diode VD1 does not pass the self-induction current when the relay is turned off.
Despite its simplicity, the photorelay circuit is highly sensitive. To set it to the required level, use the resistor R1.
The supply voltage is selected according to the parameters of the relay and is 5-15 V. The winding current does not exceed 50 mA. If you need to increase it, you can use more powerful transistors and relays. The sensitivity of the photo relay increases with increasing supply voltage.
Instead of a photoresistor, you can install a photodiode. If a sensor with increased sensitivity is needed, circuits with phototransistors are used. Their use is advisable in order to save electricity, since the minimum limit of operation of a conventional device is 5 lux, when the surrounding objects are still distinguishable. The threshold of 2 lux corresponds to deep twilight, after which darkness sets in 10 minutes later.
It is advisable to use a photorelay even with manual lighting control, since you can forget to turn off the light, and the sensor will "take care" of this on its own. Easy to install and affordable.
Photocell specifications
The choice of photorelay is determined by the following factors:
- photocell sensitivity;
- supply voltage;
- switched power;
- external environment.
Sensitivityis characterized as the ratio of the resulting photocurrent to the magnitude of the external light flux and is measured in µA/lm. It depends on the frequency (spectral) and light intensity (integral). To control lighting in everyday life, the last characteristic is important, depending on the total luminous flux.
The rated voltage can be found on the device case or in the accompanying document. Foreign devices may have different voltage standards.
The load on its contacts depends on the power of the lamps to which the photorelay is connected. Lighting photorelay circuits can provide for direct switching on of lamps through sensor contacts or through starters when the load is high.
Outdoors, the twilight switch is placed under a sealed transparent cover. It is protected from moisture and precipitation. When working in the cold period, heating is applied.
Factory made models
Earlier, the photorelay circuit was assembled by hand. Now this is not necessary, as the devices have become cheaper, and the functionality has expanded. They are used not only for external or internal lighting, but also for controlling plant watering, ventilation systems, etc.
1. Photorelay FR-2
Prefabricated models are widely used in automation devices, for example, to control street lighting. You can often see burning lanterns during the day that you forgot to turn off. With photo sensors there is no need for manual lighting control.
The fr-2 photorelay circuit of industrial production is used for automatic control of street lighting. Here, too, the switching device is relay K1. A photoresistor FSK-G1 with resistors R4 and R5 is connected to the base of the transistor VT1.
Power is supplied from a single-phase 220 V network. When the illumination is low, the resistance of the FSK-G1 is large and the signal based on VT1 is not enough to open it. Accordingly, the transistor VT2 is also closed. Relay K1 is energized and its working contacts are closed, keeping the lights on.
When the illumination increases to the operating threshold, the resistance of the photoresistor decreases and the transistor switch opens, after which relay K1 turns off, opening the lamp supply circuit.
2. Types of photorelays
The choice of models is large enough to be able to choose the right one:
- with a remote sensor located outside the body of the product, to which 2 wires are connected;
- lux 2 - a device with high reliability and quality level;
- photorelay with 12 V supply and load not higher than 10 A;
- DIN-rail mounted timer module;
- IEC devices of domestic manufacturer with high quality and functionality;
- AZ 112 - high sensitivity machine;
- ABB, LPX are reliable manufacturers of European quality devices.
Methods of connecting a photorelay
Before purchasing a sensor, it is necessary to calculate the power consumed by the lamps and take it with a margin of 20%. With a significant load, the street photo relay circuit provides for the additional installation of an electromagnetic starter, the winding of which must be switched on through the contacts of the photo relay, and the load should be switched with power contacts.
For the home, this method is rarely used.
Before installation, the mains voltage ~ 220 V is checked. The connection is made from a circuit breaker. The photosensor is installed in such a way that the light from the flashlight does not fall on it.
The instrument uses terminals for connecting wires, which makes installation easier. If they are missing, the junction box is used.
Due to the use of microprocessors, the photorelay connection scheme with other elements has acquired new functions. A timer and a motion sensor have been added to the algorithm of actions.
Convenient when the lights automatically turn on when a person passes through the landing or along the path of the garden. Moreover, the operation occurs only in the dark. Due to the use of a timer, the photorelay does not react to the headlights from passing cars.
The simplest scheme for connecting a timer with a motion sensor is serial. For expensive models, special programmable circuits have been developed that take into account various operating conditions.
Photo relay for street lighting
To connect the photorelay, the circuit is applied to its body. It can be found in the instrument documentation.
Fromthree wires come out of the device.
- Neutral conductor - common for lamps and photorelay (red).
- Phase - connected to the input of the device (brown).
- Potential conductor for supplying voltage from the photorelay to the lamps (blue).
The device operates on the principle of phase interruption or inclusion. Color coding may vary from manufacturer to manufacturer. If there is a ground conductor in the network, it is not connected to the device.
In models with a built-in sensor, which is located inside the transparent case, the operation of street lighting is autonomous. It only needs to be powered.
Options with the removal of the sensor are used when the electronic filling of the photorelay is conveniently placed in the control panel with other devices. Then there is no need for a stand-alone installation, pulling power wiring and maintenance at height. The electronic unit is placed inside the room, and the sensor is taken out.
Features of a photorelay for street lighting: diagram
When installing a photo relay outdoors, there are some factors to consider.
- Availability of ~220 V supply voltage and matching of contact and load powers.
- Do not install devices near flammable materials and in aggressive environments.
- The base of the device is placed at the bottom.
- Swinging objects such as tree branches should not be placed in front of the sensor.
Wiring is done through the outdoor junction box. It is fixed next to the photo relay.
Select photocell
- The ability to adjust the response threshold allows you to adjust the sensitivity of the sensor depending on the time of year or in cloudy weather. The result is energy savings.
- Minimum labor is required when mounting a photo relay with a built-in sensing element. It does not require special skills.
- The timer relay is well programmed for its needs and operation in the set mode. You can set the appliance to turn off at night. The indication on the body of the device and push-button control make it easy to set up.
Conclusion
The use of a photorelay allows you to automatically control the period of switching on the lamps. Now there is no longer a need for the profession of a lamplighter. The photorelay circuit without human intervention in the evenings turns on the light on the streets and turns it off in the morning. Devices can control the lighting system, which increases its life and makes operation easier.
