For the rational operation of electrical devices, automated control systems are used. A programmable time relay is capable of performing a lot of useful functions, including turning on and off devices according to a given algorithm.
What is a time relay
From French, the word "relay" is translated as "replace", but in practice, the term denotes an electrical or electronic key, which is necessary for switching sections of electrical circuits and controlling electricity consumption. This concept is typical for conventional electromagnetic devices. The programmable device, or timer, gives the command to connect or disconnect electrical circuits automatically, according to the settings set by the user.
An electromechanical device closes or opens contacts when a small electric current is applied to the coil winding of the relay. The resulting magnetic field sets in motion the "armature" to which the switching contacts are connected. Thanks to this process, the network is opened and closed. Recently, solid state relays have been widely used. They have powerful semiconductor switches and are capable of withstanding heavy loads.
If the circuit needs to be switched not during the period of the signal, but at a certain moment, a more complex device is used - a time relay (RV). They fire after a certain period, providing a sequence of actions. Thanks to the principle of operation, it is possible to build electrical circuits of different complexity. With the help of such circuits, control functions for various equipment are carried out.
For example, a relay is indispensable for organizing automatic watering, turning off the lights in the common corridor, turning on and off the compressor in the aquarium.
Operating principle
The main function of the RV is the formation of a time delay for switching control groups of contacts. The implementation of the delay depends on the design features of the device. There are many types of RVs. From a functional point of view, they are pneumatic, motor, electromagnetic, electronic, as well as devices on the clockwork. They differ in parameters, appearance and installation method, they have the following technical characteristics:
- maximum switched current;
- rated switching voltage;
- type of contacts, their number;
- wear resistance (estimated number of inclusions);
- IP protection degree.
The electronic timers indicate the rated supply voltage and power consumption. And also the period of storage of programmed data in memory in case of power failure. The presence of an informative screen and a control system makes it possible to simultaneously support several tasks.
Devices are divided into devices with a delayed switch-off or switch-on. Many relays have two options at once, changing the type of commutation. The work algorithm is as follows:
- During start-up, the contact group is triggered - the contacts close for the relay with the off-delay.
- The time delay mechanism is cocked.
- At the end of the programmed interval, the contact group changes order.
The relay on delay works in a similar way. In devices of the cyclical type, the given sequence is repeated many times.
What elements does the time relay include?
The relay can be self-powered, connected to the network and an input for an electrical device. In this case, the relay is an independent controlled socket.
Built-in devices are part of an electrical appliance and do not have their own housing. An example is the programmed operation of a microwave oven, electric oven or washing machine.
The program is set manually. The required time interval is set after which the relay will switch the electrical circuit. If necessary, you can program a specific day of the week, weekend or work shift. The device has parameters that explain its programmable functionality:
- possible range of time delay (in seconds, minutes, hours, days);
- number of commutations;
- features of settings;
- time error per day, in seconds.
Electronic RVs have a magnetic circuit, a control winding and a short-circuited loop. They are equipped with computer I / O ports, which greatly expands the functions of the device. The different types differ in the number of inputs and outputs, switching capacity, type of current, voltage and number of setting steps. Some of them allow online monitoring of connected relays and display of related information.
The scheme of the device
Time relay with delayed shutdown 220V RZV-1 is used in automation circuits, for example, on a staircase, for a fan in a bathroom. The response time range is from 1 second to 60 minutes. To set the time, you need to press and release the "PROG" button. The contacts open, and the time until the next press is saved in the device's memory.
To change the delay period, the operation is repeated. The minimum delay is 1 second, if there is no repeated pressing, the relay will work after 60 minutes. The device memory will record the maximum delay time - 1 hour. When the contact is closed, the relay is switched on, when the contact is opened, the timer is turned on. PB disconnects the load after a specified time.
The contact can be represented by both a momentary pushbutton and a conventional switch. When switching, a light bulb or any other load is turned on and the programmed time begins to count down. At the end of the specified period, the device will turn off.
An adjustable device with a digital scale - a socket with a timer, widely used at home, makes it possible to control any household appliances. The action time is adjustable in a daily range, which is quite enough for daily use. The instruction explains how to set the disc pointer to the current time. The design of such a mechanical relay allows you to organize up to 48 switching on during the day.
Relay testing
Electronic devices operate on the basis of digital pulses. Modern devices have high-performance microprocessors. Usually PB is designed for switching inductive or non-inductive loads. To configure a digital type device, you will need to enter the required time parameters using the function keys. The possibility of wide customization allows you to set not only seconds, but also days of the week.
The purpose of testing is to understand the design and operation of the time relay. Checking the device when it is turned on again is performed in the following sequence.
- External examination and check of the mechanical part.
- Checking the operation of the spark extinguishing circuit.
- Rectifier testing.
- Determination of the resistance to current of the winding circuit.
- Voltage check on pickup and return.
- Response time control.
Testing of the main parameters is carried out using a special device. When inspecting the mechanical part, corrosion and contamination are revealed. Check the travel and balance of moving parts, the condition of the axles and springs, the tightening of the screws and the axial play.
An important point is to check the strength of the insulation. The voltage is applied alternately to all bases and clamps. The insulation must be capable of withstanding 1000 V at an AC frequency of 50 hertz.
The probable error lies in the soldering, the leads of the coils and resistances. And also at the place where the conductor passes through the hole in the board, plastic washers that fix the contacts on the axis.
Other functions
Modern control systems have a variety of capabilities. In some models, the additional functions of the programmable relays are displayed in three main and two mixed modes, which are indicated as follows:
- H - weekly timer;
- U - voltage relay;
- F - photo relay;
- HU - voltage controlled weekly timer;
- FU - photo relay with voltage control.
The weekly timer automatically performs a daily important function. For example, optimization of the parameters of a greenhouse or hatchery. Can control the operation of fountain devices, advertising structures.
Relay U protects electrical equipment from possible fluctuations in the mains voltage. The connected device shows its real value on the display.
If the value is within the specified limits, the load is switched on. When the voltage goes beyond the upper or lower threshold, the load is not connected.
The photo relay is the best option for the programmed operation of lighting fixtures. It can be used both in everyday life and to control the illumination of various structures, illumination of garden and park squares, streets, and other public places.
There are also devices that combine the functions of a timer, photo relay and voltage relay. The non-volatile memory of such a device allows you to save the programmed parameters not only during voltage surges, but even during power outages. Typically, the permissible load current value for the relay of the device is up to 16 amperes. If the operating current is higher, the equipment is equipped with a magnetic starter or contactor.
The listed devices are intended for switching the load, according to the set time, monitoring the voltage and disconnecting consumers with significant fluctuations in the electrical network. Moreover, after the parameters are restored, they are automatically turned on. The switching of the set illumination level, other programmed actions is carried out.
Time relay advantages
Analog and digital time relays are very convenient for controlling executive circuits of various household and industrial devices.
An on and off relay has a number of positive factors:
- optimizes the performance of household electrical and pumping devices;
- saving energy resources when connecting the "smart home" system;
- switching of production equipment, mechanisms and other devices;
- settings allow you to select a mode that is convenient for an individual user;
- installation of cyclic shutdown and inclusion is possible;
- the device is triggered by a sound signal.
In everyday life, a timer is used to operate a fan, refrigerator, air conditioner, and optimize lighting. The device can be used in educational organizations, workshops and schools, for example, to make a call. Farms install a special artificial light for the growth and development of animals. In production, using relays, various machines and mechanisms are turned on and off.In agriculture, the relay controls irrigation and irrigation systems, pumping stations and ventilation units.
What to look for when buying
To select a suitable model, you should be guided by the basic parameters of the device. Various models can be connected to a 220 V household network, as well as to reduced management networks of 12, 42 and 127 V.
The throughput of the contacts without overheating depends on the permissible load current. Where conditions do not allow switching contacts due to explosion hazard, non-contact devices must be installed.
Indicators of protection against moisture and temperature conditions determine the permissible parameters of the operating environment. For the relay to work correctly, you should pay attention to the following nuances:
- preference should be given to devices with a wide possibility of setting the time;
- the control panel should be simple and straightforward;
- the picture of the display is clear and bright;
- numbers and icons are clearly visible, easy to read.
An uncomplicated programming language, the ability to move from outdated systems based on relay-contactor circuits to microprocessor devices have allowed programmable relays to take their rightful place in the market for new automation devices.
