How to connect a time relay: cyclic, mechanical and electronic

There are many electrical devices and samples of industrial equipment that are characterized by an intermittent operating cycle. They turn on for a certain time, after which it is required to remove the electrical voltage from them. The owner has to constantly be distracted, watching the products connected to the source. This function can be performed by modern time relays, which make it possible to automatically disconnect the load from the network after a fixed time interval (it is called a delay). It can be set by the user himself, having calculated the required moment of switching off the consumer in advance.

What is a time relay

The time relay is an electromechanical (electronic) device, the main purpose of which is to automatically disconnect the load with a certain delay. Devices of this class are widely used in power grids of industrial installations, allowing them to control their operating modes without human assistance. In addition, time relays are used in everyday life, ensuring the timely removal of 220 volts from the devices connected through them. The following can be used as such loads:

• household illuminators of any type;
• samples of climatic equipment;
• ventilation systems and other devices.

The use of modern devices with a time delay can significantly reduce energy consumption and make life easier for the average person.

The first samples - mechanical prototypes of these devices - were developed in the middle of the 19th century. They controlled the switching on and off of the lines of the then developing telegraph communication. Since then, these products have been significantly improved, their functionality has increased markedly. At the same time, the principle of operation of such devices remained the same: after a specified period of time, the actuator is triggered, after which the supply voltage is automatically removed from the load or supplied to it. In industrial equipment control systems, the controlled circuits are switched according to a certain algorithm, set by programming the electronic relays.

Work algorithms, functional diagrams, conventions

In modern programmable devices, a complex algorithm of operation is provided, including time pauses and cyclically repeating intervals. There are the following schemes for the functioning of the time relay:

• simple delay of the moment of switching on;
• after power is applied, the load is connected, but after a time specified by the program, the voltage is removed from it;
• the same as in the previous case, but the disconnection occurs with a certain delay.

Another scheme assumes a more complex cyclic mode of operation of the device. To understand it, you should clarify the order of switching on and off the load. It looks like this:

1. After supply, the power is supplied to its destination only after a certain time interval.
2. The line remains connected to the network for a predetermined interval.
3. There is a shutdown and a pause equal to its duration when power is applied.
4. The load is reconnected for the same time as the first time.
5. The sequence of these actions continues until the supply voltage is completely removed.

When studying the algorithms for triggering the time relay and the features of its application, you will need to familiarize yourself with one of the most important characteristics of the device, presented in the form of a functional diagram.

Tripping diagrams

This characteristic is understood as graphical diagrams describing the state of the time relay at different points in time. Upon acquaintance with them, the entire switching process is presented in a visual form.

The cyclical nature of the processes observed during the operation of devices according to a complex algorithm is especially clearly discernible in the diagrams. The time intervals indicated on them, as a rule, are set by the user himself. On the other hand, there are known samples of devices in which the moments of disconnection and connection of the load cannot be corrected. As a fixed parameter, they are usually indicated in the product passport. Most often, these are special-purpose timing devices installed in protective circuits of industrial installations.

In each individual sample of the time relay, several work algorithms are provided at once, selected at the discretion of the user. The appearance of the functional diagrams is shown on the body of the product; there you can also familiarize yourself with the location of its contacts.

Designations of contacts on diagrams

When choosing a time relay, it is important to learn to understand not only the functional operation diagrams, but also the layout of its working contacts. Among them, the following types of contact groups stand out:

• one of them in the inoperative position is always open;
• another group of contacts in normal conditions is in a closed state;
• the third variety is neutral.

To understand the nature of the relay operation on the diagrams, they are indicated by special icons in the form of semi-ovals, segments of straight lines and truncated parallels.

Relay types

All relay devices are divided into the following classes according to the method of connection to the current electrical network:

• block type devices;
• switches built directly into the electronic circuit;
• modular designs.

Block-type devices are made in the form of a monolithic adapter plugged directly into the outlet. Their contacts are directly connected to the phase and zero of the switched circuit. Embedded samples do not need a third-party power source, as they work as part of complex electronic circuits.

Modular time relays are mounted on a DIN rail in a switch cabinet and connected to the adjacent neutral and phase bus. In accordance with the design features of a particular actuator, all known relay samples have the following versions:

• electromagnetic type;
• devices made on the basis of an electronic circuit;
• pneumatic and electromechanical devices similar to winding mechanisms (the latter in appearance resemble watches).

In private practice, electronic and electromagnetic devices are widely used, which is explained by the simplicity of their design and relatively low cost.

By the type of mechanism that provides a time delay, these devices are divided into the following classes:

• with electromagnetic deceleration;
• pneumatic (compressor);
• with a clock (anchor) retarding mechanism;
• motor systems;
• electronic-mechanical analog devices.

Each of the listed samples differs from analogs in its characteristics and is used in specific conditions at the discretion of the user. Modular structures installed on a DIN rail can be used as a 220 Volt temporary relay for lighting indoor spaces.

Weekly digital timer

The digital weekly timer or electronic time relay is a flexible programmable device designed to operate within seven calendar days. With its help, it is possible to set the exact dates of the necessary commutations (connections or disconnections of specific loads) in public institutions such as schools, offices and similar places for collective use.

In the "advanced" samples of daily time relays, it is possible to save copies of several programs with the ability to read. Various types of storage devices are used as information carriers, allowing you to remove it using the D KEY electronic key (in the version of PLUS and SYNCHRO systems).

Setting up Electromechanical Analog Relays

Industrial ACS systems and some household devices are often equipped with devices of an electromechanical type, for the normal operation of which special adjustment is required. On their front panel there is a slotted potentiometer knob, which can be rotated using a screwdriver with a thin blade. Along the entire circle next to it there is a marked scale of gradations for setting the time.

Some models have an LED status indication on the bezel. To set the desired interval, it is enough to turn the potentiometer rod with a screwdriver to the corresponding mark with the value in minutes or hours applied next to it. Devices of this class (NTE8 type, in particular) are widely used in ventilation control circuits in a house, heating modules, as well as in artificial lighting systems.

Adjustment of instruments with a digital scale

The setting of devices of this type is illustrated by the example of a timer with a digital scale of the "REV Ritter" brand, plugged into a regular power outlet. The period of validity of its time delay, as a rule, is limited to one day, which is quite enough for living conditions. Instructions for setting up such a relay include the following items:

1. Plug the device into a power outlet.
2. Move up all the adjusting elements (segments) set along the circumference of the tuning dial.
3. Move down only those that correspond to the set time.
4. The center dial pointer is set to the current time.

If the segments located between the digits 18 and 20 are shifted downward, the required load will turn on after the 18 hour interval and turn off after two hours. The design of such a semiautomatic device provides for the possibility of organizing up to 48 working cycles (on and off) within two calendar days.

Connection to the control circuit

A classical scheme is used, which allows switching a multi-position load according to a time criterion (in this situation, the number of states is 2). Devices of this class must be accompanied by a technical passport, which describes not only their design, but also the order of connections.

On some models of electronic-mechanical and digital timers, the circuit is printed directly on the body of the device.

The classic switching option is presented in the following sequence of operations:

1. When connected to the mains, power is supplied directly to the terminals of the device.
2. Through the built-in automatic circuit breaker, the phase voltage is supplied to the winding of the executive relay.
3. Its contactors connect the circuit directly to the power line.

The connection principle for most relay devices is essentially the same. When power is applied to it, an internal circuit is triggered, due to which voltage is supplied to the load through a group of switched contacts.