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Time Delay Relay Circuit Diagram Symbol Working Principle Main Types

Time Delay Relay Circuit Diagram Symbol Working Principle Main Types

December 05 , 2023 0

Relays are a construction element used to control high power with very low power consumption while also being used to process signals, they can also be used like switches. Under normal circumstances, a common relay is an electrical device that functions like an electric switch. Once the current reaches the coil of the relay, the open contact will close and the closed contact will open. Once no current is flowing in the relay coil, the contact will return to its original position.

Basic Concept

A relay with a timing element device is called a time delay relay, and the device is intended to delay the immediate switching of the power on/off when the power is applied or removed from the relay board. The delay device has a built-in delay function, so the relay does not activate immediately after activation, but will wait for a fixed period of time.
Therefore, this relay is suitable for situations where a delay is required before the relay is activated, such as security systems and industrial automation. Some types of delay relays have a shock absorber system connected to the armature that avoids full movement once the coil is activated or deactivated.

The figure above shows the symbol when the power is on

Above is the symbol when power is off

Working Principle

Time delay relays work by simply controlling changes in contact state by activating or deactivating the timer. Whenever the timer is activated or deactivated, the timer counts from "0 "to the current time, which is called the cumulative time. When the preset time and the accumulated time are equal, the timer contact changes the state.

Main Type

There are currently different types of time delay relays available for different methods of operation and sizes. Normally, relays change their mode of operation. Of course, there are other types of multifunctional time relays available. Therefore, depending on the application requirements and other factors such as accuracy, price and switching action, time delay relays can be selected.

Time Delay Timer Relay

This is the most commonly used type of delay time relay. Once the input voltage is applied, the relay will start timing and energize the output after the set time. When the input voltage is removed, it will disable the output after the relay is reset. These relays are primarily used in applications where it is necessary to ensure that a program has occurred before starting another program. The main applications of this type of relay are as follows:
Used for blower motor to delay blower start.
Used for anti-asset alarms to delay the sound of the alarm by allowing authorized personnel to leave the house for a period of time.
Operate the door lock, once powered, the door lock should wait a few seconds to check that the door is closed before locking it.
Used for fan control.

Disconnect The Delay Timer Relay

This timer relay needs a trigger to start timing once the input voltage is obtained. The output of this relay will be energized when the trigger is applied, and the trigger must be disconnected to enable the time delay. At the end of the delay period, the output is powered off. One day provides the trigger throughout the delay period and it will reset.
- And the thermostat turns off the cooling compressor, these timers are used in AC systems to hold the blower motor for a specific period of time. These are also used to operate motors and electrical equipment for a fixed period of time, such as coin-operated dryers in commercial laundries. Other applications include telephone circuit control, elevator door control and gas valve control.

One-Time Timer Relay

Secondary timer relays are also known as interval action time relays, single pulse timers, single interval timers, and single timers. As the name suggests, this relay only triggers
The main function of the secondary relay is to trigger the circuit after a fixed period of time. These relays are activated by a power source. Once energized, the contact of the relay will move to a different position and remain in that position for the time set before returning to its unique position. These timers are often used in industrial environments, such as operating machinery with start or stop buttons, and also in welders to adjust spot welding times.

Interval Timer Relay

Interval timers are primarily used to control the time it takes to energize an electrical load, these types of time delay relays are also known as bypass timing relays interval delay relays pulse shaping and energizing delays via instant transmission timers. These relays work by delaying power to the load until a specific time has passed.
When the timer ends, it will be powered on and kept on until the timer terminates. At this position, the power supply is disconnected from the electrical load and turned off until powered on again.

Recovery Timer Relay

This type of time delay relay is mainly used for the cycle of switching loads, also known as repeat cycle timers. These are very helpful for saving energy by turning the load on and off regularly, and they also produce a flicker effect. These are multifunctional or single-function devices. These types of time delay relays are often used in applications that require cyclic power supply to electrical systems or equipment.
A common application for recovery delay timer relays is to turn the compressor on and off again at normal intervals in HVAC systems. Therefore, this helps prevent the system from overheating. It is also used in electrical equipment to turn the device on and off at specific time intervals.

Flash Timer Relay

The contacts in this type of time relay are periodically powered on and off continuously. Normally, this occurs after the input voltage is applied. These time-delay relays are often used in different applications where it is necessary to specify that a process or system is running. These are also used in emergency lighting systems, as long as the lights should flash at normal intervals to indicate that the system is working.

How To Test Time Delay Relays

The time delay relay can be tested by load test method. The specific steps of the test are given below

First change the timer with a high delay, for example, 2 minutes
Activate the relay with 125V and measure the DC current.
Before the timer starts, write down the current value.
After two minutes, the relay pulls in. Note the current value after the action.
Measuring relay power (W)=125vx measuring current

Main Application

The main applications of time delay relays include the following common areas
Mainly involved in different commercial and industrial applications, such as construction, machinery, HVAC, water, etc.
It is often used in machine-control based applications to provide switching for circulating machinery. Therefore, this helps to avoid damage or jamming of the equipment. Can be used to delay multi-line switching in greenhouse or production services. Therefore, this helps to save energy for irrigation systems and pump controls by simply avoiding turning on lights when they are not needed.
Used in HVAC systems to control centralized water supply systems and fans. Therefore, this helps to save energy and keep the building very comfortable.
Once a fixed period of time has passed, these relays trigger an alarm. So this is very useful for monitoring and security purposes.