Photoresistors are semiconductor resistors whose resistance changes under the influence of electromagnetic radiation in the optical range.
The photosensitive element in such devices is a rectangular or round tablet pressed from a semiconductor material, or a thin layer of a semiconductor deposited on a glass plate - a substrate. The semiconductor layer on both sides has leads for connecting a photoresistor to the circuit. On circuit diagrams, a photoresistor is indicated by a resistor sign in a circle with side arrows.
The electrical conductivity of a photoresistor depends on the illumination. The brighter the lighting of the device, the lower the resistance of the photoresistor and the greater the circuit current.
These devices are used in automatic control circuits.
Photodiodes are a type of semiconductor diode. Until the photocell is refreshed, the blocking layer prevents the mutual exchange of electrons and holes between the semiconductor layers. When irradiated, light penetrates the “p” layer and knocks electrons out of it. The released electrons pass into the “n” layer and neutralize holes there. A potential difference arises between the photodiode terminals, which can be amplified by an electronic circuit to turn on automation and telemechanics devices.
Photodiodes are used to assemble power batteries in everyday life and on spacecraft.
Phototransistors are photocells based on transistors. This photo lighting relay uses a direct conduction phototransistor. To ensure that the light flux reaches the semiconductor crystal, the transistor cover is removed by simply removing it with pliers.
The photo relay in the figure above is used to automatically turn off or turn on actuators when the lighting changes.
Resistor R1, R2 and phototransistor VT1 represent a voltage divider based on transistor VT2. When phototransistor VT1 is illuminated, the voltage at the base of transistor VT2 decreases, transistor VT2 closes, and VT3 opens.
Relay K1 is triggered by the passage of current and opens contacts K 1-2, power supply to the load stops. Diode VD2 protects transistor VT3 from pulse noise that occurs when switching current in the winding of relay K1.
Relay contacts can be used to switch automation and telemechanics actuators.
Resistor R1 sets the sensitivity threshold, and R4 the illumination threshold.
LED HL1 indicates power on and operation mode of relay K1. Capacitor C1 prevents the relay from operating in the presence of interference. The power supply of the relay circuit is stabilized by the DA1 analog microcircuit. Capacitors C2, C3 are included in the anti-aliasing filter. Diode bridge VD1 is selected for a current of up to 1 ampere and a voltage of 50-100 Volts.
The device is equipped with a power switch S1 and a fuse F1.
The design of the VT1 phototransistor is simple: the “cap” of the transistor is removed with pliers, the transistor is glued to the M.8 nut, and the nut with the transistor is to a piece of glass and attached to the device.
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Phototransistor |
according to the drawing |
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Transistor |
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Transistor |
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Resistors |
Type-A variables |
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A correctly assembled device should work immediately. When the slider of resistor R1 is in the upper position and resistor R4 is in the middle position, when lighting is applied to phototransistor VT1, relay K1 should operate. First check the relay by directly turning on the 12 volt power supply. Use resistor R1 to “adjust” the sensitivity of the photo relay at a given lighting R4.
List of radioelements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| DA1 | Linear regulator | LM7812 | 1 | To notepad | ||
| VT1, VT2 | Bipolar transistor | MP42B | 2 | To notepad | ||
| VT3 | Bipolar transistor | MP25B | 1 | To notepad | ||
| VD1 | Rectifier diode | 1N4005 | 4 | To notepad | ||
| VD2 | Rectifier diode | 1N4007 | 1 | To notepad | ||
| VD3 | Diode | KD512B | 1 | To notepad | ||
| C1 | 10 µF | 1 | To notepad | |||
| C2 | Electrolytic capacitor | 1000 µF 16 V | 1 | To notepad | ||
| C3 | Electrolytic capacitor | 100 µF | 1 | To notepad | ||
| R1 | Variable resistor | 100 kOhm | 1 | To notepad | ||
| R2 | Resistor | 1 kOhm | 1 | To notepad | ||
| R3 | Resistor | 3.3 kOhm | 1 | To notepad | ||
| R4 | Variable resistor | 100 Ohm | 1 | To notepad | ||
| R5 | Resistor | 1.1 kOhm | 1 | To notepad | ||
| HL1 | Light-emitting diode |
To control the operation of many electrical devices, special controllers are required, which are responsible for the accuracy and correctness of their operation. We propose to consider how to connect a simple street photo relay, what it is and its operating principle.
Description of photo relay
Sensitive photo relay based on a triac GOST 51324.2.1-99. is an optocoupler device consisting of LEDs optically connected to the contacts of electrical appliances. It is also often called a twilight LED sensor, a day-night device, etc.
Photo – Photo relay photoPhoto relays are offered various advantages Compared to mechanical time relays:
- Small size. Housed in small units such as USOP, the fixture is designed with a reduced board;
- Long service life. In the absence of mechanical contact, the shelf life is significantly extended due to the fact that wear is completely absent;
- Low current drive. This device can operate with an incoming current of even a few milliamps without an amplifier. Thus, neighboring devices can do without drivers;
- Quiet operation. In the absence of mechanical contact, the contactless relay does not make any sounds during operation;
- High speed. Photo relays are about 10 times faster than their mechanical counterparts (which take a few milliseconds to switch).
- Excellent performance, many appliances come with a timer.
The components of the device are: three contact wires for connecting to a common network, a magnetic starter, and an armature.
Photo – Photo relay disassembled Video: simple photo relay
Operating principle
The diagram shows the principle of operation of the device. Photoresistor PR1 reduces its resistance to several Kohms as the illumination increases, due to which phototransistor VT2 opens, which turns on photorelay K1, and this device, in turn, will begin to transmit signals. Diode VD1 protects the circuit from self-induction. Thanks to this principle, even very weak signals can turn the light on or off.
Photo – Photo relay circuit The main working part is a photocell, which is a gas tube in which gas ionization occurs. It has a cathode that is capable of producing electrons in proportion to the intensity of light directed towards it, and the tube is also equipped with an anode to collect electrons.
Photo – Photo relay Whenever a negatively charged surface is placed in an atmosphere of an ionizable gas, such as mercury vapor or any inert gas, electrons are transferred to it. There, by using the Fermi-Dirac velocity theory, electrons are accelerated depending on the strength of the applied electric field.
Photo – Photo relay TDM These electrons travel a relatively short distance before colliding with an ionizing gas atom. When an electron, which has constant kinetic energy, passes through an ionizing substance, it disturbs the atoms it encounters. Also, its trajectory of action may change periodically. If the material is gaseous, the resulting fragments or ions may move away from each other. But if electrons are knocked out of atoms, then they move in one direction, and the residual positive ions move in the opposite direction. The output of the ionization type or photocell depends on the number of electrons at the anode.
It is the movement of electrical particles in a certain sequence that causes the device to switch. It must be said that this is especially convenient for devices with a motion sensor Finder, Legrand.
Application and connection
Electronic devices with a built-in photosensor of light are used to organize and control automatic street lighting, external façade, driveway or household lighting. Often combined with it, console lamps of the housing and communal services type are used, which are equipped with protective glass and a special grille.
The device operates on a very small microcircuit and transistors, and instructions are often given on the case on how to properly connect the device. We use a light control switch to demonstrate step by step how to install the fixture. Despite its externally small size, this device does an excellent job of lighting courtyards, parks and gardens.
Photo – photo relay FR-3 In general, photo relays for street lighting are recommended to be installed in the middle position. To install the switch yourself, you need to use a special bracket that is attached to the wall. The canopy is installed directly into the photo relay using a screw. The installation location depends on the lighting; try to choose an area where nothing prevents the sun's rays from hitting the working surface of the device, otherwise interference will begin on the photodiode and the device will not work correctly. Depending on the characteristics of the device, the presence of trees, furniture, curtains, etc. in front of the photo relay is not allowed.
The diagram of the photo relay and its principle of connecting to the network is most often depicted on the box of the device, it is very convenient, you do not need to look for one that is suitable specifically for your device. Detailed instructions How to connect a photo relay with your own hands:
- There are three wires coming out of the relay: brown, blue and red. Based on standard parameters and indicators, brown is a phase cable, red is an extension wire, goes like switching to a lamp, blue is zero (if you are developing a homemade relay, then you need to take these branches into account);
- In order for everything to be connected correctly, it is necessary to connect the wires to the console lamp as a load, this is demonstrated by the circuit designation.
To check that the connection is correct, you need to plug in the starter and see if the spotlight or flashlight works.
Photo - Connecting a photo relay Relay installation and grounding
If a TN-S or TN-C-S type grounding system is used in an apartment, house or street, the electrical circuit is powered from the network by a three-wire cable (phase wire, neutral, ground). But for connecting lamps with TN-C type wiring, the connection will differ only in that there is no PE conductor.
The adjustment is made according to the manufacturer's settings. Before connecting the lamp, be sure to check the passport, certificate and patent of the seller, so that later you do not have to make major repairs to the wiring in the apartment. It is advisable to install a separate machine for this controller in the distribution board (cabinet).
You can buy a photo relay at any electrical store; the price directly depends on the brand and area of operation (street - FR-601 IEK, FR-602, facades - FRSU-1-0 uhl 4.2, FRSU-2-0 and other types). The most popular models are FR-1 12 volt, UTFR-1M, CSM, LUNA 110 AL, TWS-1, TWS-1M, AWZ-30, ABB (ABB), LXP-01, DLS-1/50, AZH-S , AS-7, RFS-11, FB-2-16A (range 2-4 kW), LUX 2.
Photo – Connecting photo relay FR-601 Yes, sometimes it is much easier to buy a light sensor in a store. But, if you need, for example, 20 of these sensors. I would argue about the profitability of such a purchase.
I am posting, in my opinion, a simple and easily repeatable photo relay circuit from those that are produced in mass production.
The tuning resistor WL adjusts the relay response threshold at illumination levels from 5 to 50 lux.
ZD1 - 24 Volt zener diode.
PH photoresistor, any with a difference of about 10 - 70 kOhm will do.
A jar of cream or any other container with a floor or transparent walls is perfect as a body.
Zero and phase do not matter when connecting. It depends on them whether there will be voltage on the lamp base when the relay is off or not.
In Fig. 1 above shows a typical lamp or load connection diagram. In Fig. 2 an option with a switch is proposed. Since sometimes when the relay is turned off, you need to force the lamp to turn on.
Photo relay board, top view.
Drawing of a transparent printed circuit board. View from above. The black stripes are "windows". Needed to prevent short circuits and sparking between conductors. They are not required, but recommended.
The board is wired for 2 types of relays. But, it can be easily redrawn to match the relays you have.
In the photo of the bottom side of the board, these “windows” are clearly visible.
List of radioelements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| Q1-Q2 | Bipolar transistor | BC857A | 2 | To notepad | ||
| D1-D5 | Rectifier diode | 1N4007 | 5 | To notepad | ||
| VD1 | Rectifier diode | 1N4148 | 1 | To notepad | ||
| ZD1 | Zener diode | 1N4749 | 1 | To notepad | ||
| R2 | Resistor | 1 MOhm | 1 | 0.125 W | To notepad | |
| R3 | Resistor | 220 Ohm | 1 | 2 W | To notepad | |
| R4 | Resistor | 560 kOhm | 1 | 0.125 W | To notepad | |
| R5 | Resistor | 1.5 MOhm | 1 | 0.125 W | To notepad | |
| R6 | Resistor | 75 kOhm | 1 | 0.125 W | To notepad | |
| R7 | Resistor | 33 kOhm | 1 | 0.125 W | To notepad | |
| R8 | Resistor | 100 kOhm | 1 | 0.125 W | To notepad | |
| R9 | Resistor | 200 kOhm | 1 | 0.125 W | To notepad | |
| PH | Photoresistor | 0-100 kOhm | 1 | To notepad | ||
| W.L. | Trimmer resistor | 2.2 MOhm | 1 | To notepad | ||
| C2 | Capacitor | 0.68uF 400V | 1 |
DIY photo relay circuit
And this is a diagram of a simple photo relay. This device can be successfully used anywhere you want, for automatic illumination of the DVD tray, for turning on the light, or for signaling against intrusion into a dark closet :) Two circuit options are provided. In one embodiment, the circuit is activated by light, and in the other by its absence.
Scheme: I used a photoresistor in place of the photodiode and a relay for the load in place of LED-2.
It works like this: when light from the LED hits the photodiode, the transistor will open and LED-2 will start to glow. The sensitivity of the device is adjusted using a trimming resistor. As a photodiode, you can use a photodiode from an old ball mouse. LED - any infrared LED. The use of infrared photodiode and LED will avoid interference from visible light. Any LED or a chain of several LEDs is suitable as LED-2. An incandescent lamp can also be used. And if you install an electromagnetic relay instead of an LED, you can control powerful incandescent lamps or some mechanisms.
A photo relay is used to automatically control the switching on and off of lights at different times of the day. An excellent solution for both suburban areas and apartment buildings.
- Device
- What can a photo relay be like?
- How to install a photo relay
Device
The simplest version of model fr 602 and other variants consists of only a few main components:
- Variable resistor.
- Diode.
- Relay for control
- Photoresistor.
- Two transistors.
The role of transistors in 602 and other models is usually played by devices designated as KT315B. They are switched on according to the circuit of composite resistors, the relay winding can cope with the load of this part. A large gain is always characteristic of such circuits. The input impedance also remains high. Thanks to this, it is possible to use a photoresistor with a high resistance value.
The photo relay circuit fr 602 for 12V assumes that the usual transistor and transistor number 2 open when the illumination of the photo device connected between the base of the first transistor and the collector increases. A current appears in the collector circuit of the second transistor mechanism, which causes the relay to operate. It turns the load on or off through its contacts, depending on user settings.
The security code with the designation KD522 is included in order to protect the device from the effects of EMF. Turning on a variable-type transistor with a nominal value of 10 oKm is necessary so that you can adjust the sensitivity of the system that connects the base and emitter in the first transistor.
FR 602 at 12 V and other power levels are used not only for house lighting, but also for street lighting. The type of circuit used depends on how many pins go to the light system. To protect against short circuits and overloads, circuit breakers are installed in the electrical panel. This is how any electrical switches work.
In this case, there are several features of nutrition.
- You need a DC voltage source of 5-15 V.
- Devices designated RES 47 or 9 are used with a source voltage of 6 volts.
- Devices with the designation RES 15 or 49 are needed when working with a voltage of 12 Volts.
There is a need to create a special board through which installation is always carried out. It would be good if it was printed. After this, to create a photo relay with your own hands, perform the following steps:
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- On the board we strengthen the variable resistor mechanism, transistors and the relay itself.
- It is necessary to create several holes in order to correctly display all the elements of the circuit.
- Using a soldering iron, we make the appropriate connections using wires.
An incandescent lamp can be used when the 602 circuit is being configured. In this case, the room should be shaded. The light flow of such a lamp can usually be adjusted.
To select the correct threshold for switching on the device, you need to work in suitable lighting conditions. A variable resistor will always help with this issue. It is necessary to install a constant resistor, not a variable one, if you do not plan to separately adjust the threshold for operation.
What can a photo relay be like?
- All modern models have control of the response threshold.
- The most expensive varieties are equipped with an additional programming function. For example, a separate program is installed to control each season. And separately by time of day.
- The presence of remote sensors is typical for frames that are not intended for installation outdoors. It is enough to use 2 wires to connect such a sensor to the internal circuit.
- In general, sensors for simple FR 602 are either remote or built-in.
- The fr itself has different purposes. For example, it is suitable for installation outdoors, then it is sold inside a sealed case. And there are options for internal installation on an electrical panel rail with the designation Din.
- Less often you can find homemade FRs, inside of which a motion sensor, a timer, and photocells are assembled together. Such designs are the most expensive. They are usually equipped with special electronic displays, thanks to which the lighting operation is adjusted as accurately as possible.
- More often you can find devices where the circuit combines photo sensors and devices that respond to movement.
How to install a photo relay
You need to use special holes to complete the installation. You just need to follow a few important rules.
- It is imperative to check what voltage the supply network operates with before installing the magnetic starter and other elements. It is necessary to have an indicator of approximately 220 V. The minimum deviation is 10 percent up or down. We also need to make sure that the protection complies with all the rules. This applies to the fuse, circuit breaker.
- Installation is prohibited if there are chemically active substances nearby. Do not place with flammable or flammable materials.
- The connection diagram suggests that the base of the device should only be at the bottom, not at the top.
- The light from the lamp being switched on should never fall on the photosensor.
Model type LXP. About the main technical characteristics
FR 601 are quite common devices that turn on and off depending on the level of illumination around. Street lighting fr 601 turns on as soon as it becomes dark outside. This solution increases the service life of any light bulbs and helps save energy.
The technical characteristics of device 601 will be as follows.
- <5 – 5o Люкс. Это обозначение рабочего показателя модели 601.
- The 601 switched circuit operates up to 10 A.
- Variable voltage, requires a power source that supports 220 Volts.
At the bottom of the device, marked 601, there is a control that allows you to set the level for lighting under normal operating conditions. The level of light and the current strength of the switched circuit are the only fundamental differences between the models of this manufacturer.
Manufacturers with the designation 601 usually provide their own settings according to which adjustment and control are carried out. Therefore, it is imperative to study the technical data sheet of the lighting product before installation. The same applies to certification documentation and patent registration. Otherwise, due to mistakes, you will have to make major repairs to your apartment or house. It is better to install a separate machine on this controller, inside a distribution board or cabinet. The scope and brand determine how much a particular device will cost.