Time relay: principle of operation, wiring diagram and recommendations for setting up
Electromechanical or electronic device, triggered upon the expiration of the designated time interval - this is a time relay. This type of devices has found wide application in electrical engineering, electrics, electronics.
Depending on the complexity of the mechanism of the device, various schemes of complexity of execution are carried out.
Due to the presence of relays in circuit solutions, it is possible to realize more flexible functions of controlling various devices.
The principle of operation of the time relay
Electronic devices are represented by a constructive variety, therefore, the principle of a time relay should be considered taking into account each structural variation separately.
From the point of view of executable actions, in practice electromagnetic, pneumatic, electronic structures and devices on the watch mechanism are used.
Option # 1: Electromagnetic Devices
Devices that support the electromagnetic principle of operation, as a rule, are designed to work exclusively in DC-powered circuits.
The response time range is usually 0.07 - 0.11 s for switching on and 0.5 - 1.4 s for switching off. The design of such a time relay contains two working windings, one of which is a short-circuited circuit in the form of a copper ring.
When an electric current passes through the main winding, an increase in the magnetic flux is noted. This current forms a short-circuited winding current, due to which the growth of the magnetic flux of the main winding is limited. As a result, a temporal characteristic of the movement of the armature of the actuator is formed, or, in other words, a time delay for switching on is created.
If the current supply to the main winding circuit stops due to the inductance effect, the magnetic field of the short-circuited winding remains active for some time. Accordingly, during this time the relay does not turn off.
Option # 2: pneumatic devices
Designs based on pneumatic systems - a kind of exclusive devices. Such devices are equipped with special deceleration mechanics - pneumatic damping mechanism.
The holding time of pneumatic relays can be adjusted by reducing or increasing the flow area of the tube through which air is supplied. For these purposes, the design of pneumatic relays are supplied with an adjusting screw.
The setting range of the time delay of pneumatic relays is, on average, 1 to 60 seconds. However, there are instances that almost double this range. However, in practice, small errors (about 10%) are noted in terms of the accuracy of response to the set values.
Option # 3: modifications of the watch type
The so-called clock time relays are widely used in electrics. This type of device is often used in the construction of circuit breakers designed to protect circuits with a voltage of 500 - 10,000 volts. The exposure range is 0.1 - 20 sec.
The principle of operation of watch models is built on the work of a spring cocked by a mechanical drive (anchor) of an electromagnet. The switching of contact groups of the hour time relay is performed after the elapsed time, the value of which was previously set on the instrument scale.
The speed of the mechanism of the device is directly related to the current flowing in the electromagnet winding. This factor allows you to configure the device under the execution of protection functions. The peculiarity of such protection is expressed by complete independence from the influence of the ambient temperature.
Option # 4: electronic relays
The last few years, almost everywhere where timers can be used, the electronic versions have replaced the outdated electromechanical models. This type of instrument has a number of advantages:
- small dimensions of the case;
- high accuracy of operation;
- convenient setting mechanism;
- visual display of information.
Electronic versions act, as a rule, on the basis of digital pulse counters. Many modern devices are built on high-performance microprocessors. Digital relays are usually designed for switching low-inductive or non-inductive loads.
To set up a digital type of time relay, it is sufficient to set the required time parameters using the function keys placed directly on the front panel of the case.The setting is usually available over a wide range of time, allowing you to cover not only seconds, minutes, hours, but also days of the week. For example, consider the model of the weekly electronic relay (timer).
How does the weekly digital timer work?
An electronic timer with automatic on-off functions can be successfully used in control circuits for various types of devices. The so-called “weekly” time relay provides switching functions in accordance with a set period of time within a weekly cycle.
For example, thanks to the device opportunities:
- switch lighting systems at a specified time;
- start or stop the process equipment;
- activate / deactivate security systems.
The device is small in size, has several function keys. Using the system keyboard, the user can easily customize (program).
Programming mode is activated by pressing and holding the button indicated by the symbol “P”. To perform a system reset helps reset key. Changing the time settings of the relay is done by setting the minutes, hours, days of the week with active programming mode.
The standard wiring diagram of the time relay provides for the installation of one of two modes of control actions - manual or automatic. The convenience of setting the digital-type relay is provided by the information LCD display.
Configure electronic-mechanical analog relays
Industrial automation systems, as well as various household modules are often equipped with electromechanical devices, the design of which involves tuning with potentiometers.
On the front panel of the case of such devices is a potentiometer rod (or several rods), intended for rotation by a screwdriver blade.A marked scale of installation values is plotted around the circumference of the rod (s).
The slot on the rod under the blade screwdriver is a kind of pointer that changes its position during rotation of the rod. By setting this pointer in front of certain values of the marked scale, the desired parameter is set.
Devices of this type (for example, NTE8) are widely used in control circuits for ventilation systems, heating modules, and artificial lighting devices.
Adjustment of devices with a digital scale
The use of devices with the functions of mechanical adjustment can be demonstrated by the example of a timer brand "REV Ritter", intended for inclusion in the network home outlet.
With the help of this device you can control almost any home appliances in a given time range. To use this daily timer, simply plug the device into an outlet and configure it.
The setting is accompanied by the following actions:
- Raise all segments located around the circumference of the adjustment disk.
- Omit only those segments that correspond to the setup time.
- Turn the dial to set the disk pointer to the current time.
For example, if the segments were dropped between the numbers on the scale 18 and 20, after the relay starts counting the time, the load will be turned on at 18 o'clock and disconnected at 20 o'clock.
In general, the design of the mechanical “REV Ritter” relay allows you to organize up to 48 switching-ons in a full 24 hours.
At the same time, the device supports the function of off-program load. To do this, there is a separate button located on the side of the case.If the user activates this button, the load is connected to the network directly, regardless of the state of the relay contacts.
Connection of time relay in control circuit
The device must be connected taking into account the compliance of the installation site with the conditions stated in the technical certificate of the device. As a rule, installation assumes vertical installation of the device with tolerances of deviation from the vertical of no more than 10º. The temperature limits of the room where the installation and operation of the time relay is supposed to usually do not exceed the range of -20ºС + 50ºС.
The level of humidity in the installation zone of the device should not exceed 80%. The electrical circuit where the timer is installed should be disconnected from the mains during installation.
A device of any design traditionally has a technical passport, where the wiring diagram is indicated. Many electronic and mechanical timers and digital timers are complemented by a circuit printed directly on the case and showing how and in what sequence to connect the time relay.
The classic connection option looks like this:
- Connect the line voltage to the power terminals of the device.
- The phase line through the circuit breaker is connected to the input contact of the load relay.
- The output contact of the load relay is connected directly to the phase line of the load.
In fact, the connection scheme for the main mass of devices is built according to an identical principle: the power supply to the device itself and the switching on of the load through a group of switched contacts.
Depending on the type of relay (single-phase, three-phase), as well as on the design features, there may be several of these contact groups.
Conclusions and useful video on the topic
Video, where the possibility of connecting the time relay. Also, this informative film tells about how the time relay differs from the timer and what functions are inherent in one or another model of electronic devices.
In fact, the possibility of using a modular device, where there are two independent time-commuting devices, is being considered. The scheme provides for the inclusion of two appliances home appliances, setting up their work in time intervals and other functions.
Of course, all existing modifications of the time relay can not be covered by one modest review.To review the entire range of devices will need to write a whole book. Actually, reference books on timers of various types are available, and if you wish, you can always find the necessary information.