What is a timer?

A timer is a device that is used to control the connection or disconnection of a circuit, all depending on the type it is, since they can be electrical, pneumatic, hydraulic, mechanical, etc.


As for its operation, it is very similar to that of a relay since the relays when receiving a pulse immediately change the position of their contacts and as for the timers, the programmed time to exchange their contacts needs to run out.

Parts of a timer

Each timer is built with totally different pieces since they do not have the same construction, nor an operating principle, such as:

a mechanical timer is made up of springs and gears, while an electronic one is made up of capacitors, resistors, integrated circuits, etc.

Although despite this all timers work under the same principle and this is: count a time and change your contacts position.
Timer blocks

Types of timers

The timers can be classified in two different ways, according to the way they act when it receives a pulse or according to the operating principle.

Pulse operation

Within this category you can find any type, regardless of whether it is mechanical, electronic or pneumatic.

To the connection

When the timer receives an activation pulse, the programmed time begins to run, once this time has elapsed, the contacts are activated or deactivated, as the case may be.

To the connection

At disconnection

This type works in reverse because the pulse must always be active and when for some reason the signal is interrupted, the timer begins to count the programmed time, when the time is complete the contacts are changed.

If for any reason the pulse is reactivated before the count has finished, it is reset until the pulse is again missing.

At disconnection

Single pulse

This timer can be calcified as one with memory, since just receiving a small momentary pulse regardless of its length activates the programmed time. To repeat the activation cycle, the activation signal needs to be sent again.

Memory timer

Operating principle

Despite the fact that timers are classified by their operation, there are different types and each one serves a specific application:

Pneumatic timer

Its operation is based on the combination of three pneumatic elements that are a spring return valve, a non-return throttle valve and an air tank.

First there is the throttle valve and this has the function of regulating the air flow that enters the tank, the more closed it is, the longer it takes to fill, once the other valve is filled it changes position indicating that the timer has finished counting time.


Electronic timer

The operation of this timer is mainly based on the charging and discharging of an electrolytic capacitor by means of an electrical resistance. Once the time programmed by the resistance is counted, the contacts are changed through an electromagnet exactly the same as the operation of a relay .

electronic timer

Synchronous motor timer

This type is built by the mechanisms used in watchmaking, but unlike these they are powered by small electric motors. They also have an electromagnetic clutch that, once the programmed time has passed, is activated to change the position contacts.


Thermal timer

This timer is composed of a bimetal sheet connected to a transformer coil that generates a constant flow of electric current that causes the bimetal to heat up and therefore change shape until it reaches the point of disconnection or connection as the case may be. .

The timing is given by the curvature of the bimetal sheet.