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What is a Timer Switch? Definition, Types, Application

In wall digital timer switch
In wall digital timer switch

The timer switch is simply a device that turns power off /on at a preset time. But that’s not all: Timer switches do more than just turn things off and on. They also provide a range of options, allowing you to set schedules. For more about the timer switch, how it works, and the benefits that you can derive from using one, continue reading below.

What is a Timer Switch?

A timer switch is described as a timing device that, using either electronic circuitry or mechanical components, controls the power to an electrical device such as a light, fan, outlet, or appliance. Let’s see what that means so you can understand the time switch better.

Timer Switch Definition

A timer switch is also sometimes called a time switch. Some people also call it a timer. Going by its name, the device should time events, that’s, switch power at a predetermined time or schedule; it does that, usually mechanically or digitally, depending on the type of timer used.

The timer switch can also be a device that you plug into your wall outlet, or a gadget that you install in/on a wall. It can also be an indoor or outdoor timer switch for street lights, security lights, or even a sprinkler system. So what are the reasons for using a timer switch?

Timer Switch Function

The main timer switch function is to eliminate the need for leaving electrical circuits or equipment running, thereby conserving energy and saving money. This ranges from having a device turn on at specific times to automatic shutoff.

Timer switches also provide added security when you are away from home, as you can program it to turn on/off for a certain period of time, simulating someone is in your home.

In today’s age of the smart home, the electrical timer switch plays an important role in providing the convenience of auto control, with digital timer switches offering the option for wireless control among other benefits.

Timer Switch Symbol

The timer switch electrical symbol is represented (in a wiring diagram) as a normal on/off, single pole single throw, type of switch. However, the symbol also includes timing icon to it. This makes it easy to spot or identify in a given timer switch circuit diagram.

For example, the symbol may appear as an on/off switch within a given schematic circuit diagram, with a timer icon on the upper or side of it. This indicates that the component is a time switch and not just a normal on/off switch in the circuit.

Mechanical timer switch
Mechanical timer switch

Types of Timer Switch

Today, you can choose from 4 main types of timer switch devices: The different types of timer switches are mechanical, digital, astronomic, and photocell timer switch. As you would expect, each type has its own advantages and disadvantages.

Mechanical Timer Switch

Also known as a mechanical timer, analog timer switch or even automatic timer switch, this is the most basic type of timer switch available. It uses physical components like springs and gears to set the timing.

As mentioned earlier, mechanical timer switches are usually manually adjusted using a knob in order to change when power is switched on and off. This timing switch has its pros and cons.

One of the main benefits of mechanical timers is that they are low cost and easy to set. However, they are also mostly bulky. A mechanical timer will also require more in terms of maintenance, given that it uses moving parts.

Digital Timer Switch

A digital timer switch is typically powered by electricity, DC or AC, and can also be called an electrical timer switch. At its heart is a microcontroller. That means it contains no mechanical/moving parts.

You can easily change the timing of a digital timer switch directly using the control buttons on its face. This allows you to quickly adjust the intervals of daily tasks or activities like to suit your needs.

Among the biggest advantages of digital time switches is their accuracy and versatility. They come with more settings that let you easily customize the timing to suit your specific needs, which means more actions from the device.

Astronomic Timer Switch

An astronomic timer, also called astronomical timer, is a type of timer that uses the position of the sun to set its timing. Usually electronic or digital, astronomic timer switches rely on a built-in memory or software program that stores the necessary data to tell them when to switch on and off.

This data includes the longitude, latitude, and other location-specific information of the device’s present location. This information is then used to accurately identify and calculate sunrise and sunset times in any given location.

From there, the astronomic time switch can be programmed to turn on or off lights, appliances, and other electronic devices at specific times of the day or night relative to the sunrise and sunset, with an accuracy level of up to a minute.

Photocell Timer Switch

In situations where you want to turn devices on and off according to the amount of ambient light present, a photocell timer is the perfect solution among the different types of timer switches.

These types of timers use an optical sensor or photodetector to detect the amount of light. This allows you to set lights to switch on when it gets dark, and off again when light comes back.

A photocell timer can be a timer switch for street light, a timer switch for security lights in a home, or business, or other uses. As you can imagine, this type of timer switch adds a whole new level of convenience to any home or business.

Timer switch wiring diagram
Timer switch wiring diagram

How Does a Timer Switch Work?

Let’s now delve into how a timer works. To understand this better, we’ll look at the two major types of timer switches: mechanical and electronic timer switch. Here’s is how each of these timers operates.

Mechanical Timer Switches

A mechanical timer switch is an analog timer that uses a clockwork mechanism to control when the power is turned on and off. This kind of switch has a knob for programming the desired time interval to turn the power on or off in hours or minutes.

A mechanical or analog timer switch can be adjusted manually to change the time that power is turned on or off. This type of timer switch has no memory, though, and every adjustment is manual.

Electronic Timer Switches

An electronic timer switch is a digital type of switch that uses an internal clock and microprocessor to control when the power is turned on and off. This kind of switch can be programmed with required time intervals in minutes, hours or days.

The electronic timer also comes with additional features like randomization settings, which vary the times each day to help prevent burglars from noticing a set switch pattern and other reasons. The digital display of this timer switch makes it easier to view and program the desired settings.

Timer switch for bathroom fan
Timer switch for bathroom fan

Timer Switch Uses

Timer switch uses are very diverse. You can install them in a home to control lights, or you can use them in commercial settings to regulate HVAC and other systems. An industrial timer switch, on the other hand, helps control different manufacturing processes. Here a just a few of the various timer switch uses.

Timer Switch for Lights

The timer switch for lights is one of the most used timers today. This type of timer offers the ability to vary lights o/off time, either for convenience, energy saving, or for security purposes. It can also be a timer switch for indoor lights, a timer switch for outdoor lights or a timer switch for street lights.

Timer Switch for Water Pump

These types of timer switches are mainly used in swimming pools and spas to control the water pump. A timer switch for pool pump, for example, can be programmed to switch on and off whenever you need, which helps to conserve energy and save you money in the long run.

Timer switch for AC

The timer switch for air conditioner allows you to regulate heating, ventilation and other air conditioning (HVAC) system functions. The timer can be set to turn the system on or off at specific times in order to maintain a comfortable temperature inside the building without wasting energy.

Timer switch for Fan

Timer switches for fans are used to regulate the speed and operation of different fan types in a home or commercial and industrial places. These can include the following: a timer switch for ceiling fan, a timer switch for exhaust fan, or timer switch for bathroom fan to help prevent moisture buildup.

Timer switch for Heater

This can be a timer switch for water heater, a timer switch for room heater, or a timer switch for space heater. These types of timer switches are used to regulate when the heating system is turned on and off, which helps to save energy by avoiding unnecessary usage.


As you can see, the timer switch is a versatile piece of equipment that you can use to control different electric circuits in your home, commercial place, or even in an industrial environment. It offers convenience, energy efficiency, and security by allowing you to set when devices like lights, pumps and AC systems are switched on and off.

Picture of William

I am William, Electrical Engineering Author. Dedicated to writing technical articles on Timer Relay, Monitoring Relay, Surge Protection Device and other electrical devices. With 7 years of writing experience, I am committed to providing accurate and in-depth expertise to my readers.


    Sir ,
    I am Looking For Such A Timer Switch Where Five Single Phase Connections Are Fed In Input and The Automatic Timer Switch Consumes Electricity for a pre fix period From one source / Connection , And Then to shift Consumption from other sources / Meters at regular pre fixed Consumption Time

    Automatic Digital Timer Switch

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