Last revised: January 16, 2025

Electromechanical timers are used to start or stop a machine or other device at preset or delayed intervals. They consist of both electrical and mechanical components, and often feature an electric motor that drives one or more gears. They typically accept electric or electronic inputs to operate a mechanical output such as rotating wheels or knobs.

Some electromechanical timers, such as the turn signals or flashers in automobiles, rely upon the thermal expansion of metal fingers.  When electric current flows through and heats these bimetallic fingers, one side expands and moves away from the switch contact. In most industrial and factory applications, however, electromechanical timers are driven by a synchronous motor that turns the cam through the switch contacts. Often, there is a friction-clutch between the cam and the gear train.

Types of Electromechanical Timers

The GlobalSpec SpecSearch database provides detailed product information about many different types of electromechanical timers. These are five common types.

Delay on timers open or close a switch’s contacts after an input signal is received and a predetermined amount of time has passed. If the switch’s contacts are normally open (NO), the load is energized. If the contacts are normally closed (NC), however, then the load is de-energized.

Delay off timers begin their timing function when the power supply is interrupted. In other words, when a predetermined amount of time has elapsed, the output relay contacts release.  Often, this capability is called delay on release, delay on break, or release delay.

One shot timers or pulse formers have contacts that change position when power is applied and remain changed for a set period. After this time period has passed, the contacts return to their normal position.

Interval delay timers are energized immediately when power is supplied or the switch input is closed. They are the opposite of delay on timers because they turn off at the end of the period. Some suppliers call interval delays a delay pulse timer. 

Recycle timers or percentage timers start their cycling function when the control switch closes. As long as the control switch remains closed, the load continues to turn ON and OFF at regular intervals. This cycling stops when the control switch is open.

Other types of electromechanical timers in the GlobalSpec SpecSearch database include position indicators, delay cycles, and preset timers. 

Specifications and Features

Electromechanical timers can be setup or programmed to perform one or more functions. They differ in terms of accuracy and repeatability, and have both minimum and maximum time intervals. Although some products can be configured for only a single time range, others can be programmed for multiple ranges or are field-selectable. 

Electromechanical timers may accept a voltage, current, frequency, or pulse as an input, and can send serial, digital, or switch outputs.

Programming options vary, and often include knobs, dials, keypads, and pushbuttons.

In terms of features then, electromechanical timers may be rated as explosion proof or include audible alarms and visual signals.

Applications

Typically, electromechanical timers are used in factories and other industrial settings. For example, they may cause a valve to open and remain open for a specified period of time, or cause a mixer to turn-on and remain running upon receiving a signal that more mix has been added.

Electromechanical Timers FAQs

How do the input and output options differ between electromechanical and digital timers?

Input and Output Options for Electromechanical and Digital Timers

Electromechanical Timers

Input Options

Electromechanical timers can accept various types of inputs such as voltage, current, frequency, or pulse.

Output Options

They can send outputs in forms such as serial, digital, or switch outputs.

Digital Timers

Input Options

The specific input options for digital timers are not detailed in the documents provided. However, digital timers are generally known for their versatility and integration capabilities with process control equipment.

Output Options

Digital timers are capable of performing complex functions and can integrate with various systems, suggesting they have versatile output options. However, specific output types are not detailed in the documents provided.

These differences highlight that while electromechanical timers have defined input and output types, digital timers are generally more versatile and integrated into broader systems, although specific input and output types are not explicitly detailed in the documents.

How do audible alarms and visual signals work in electromechanical timers?

Electromechanical timers can be equipped with features such as audible alarms and visual signals to enhance safety and operational efficiency in industrial settings. Here's how these features typically work:

Audible Alarms

Function: Audible alarms in electromechanical timers serve to alert operators to specific conditions or the completion of a timing cycle. This is particularly useful in noisy industrial environments where visual cues might be missed.

Operation: When a timing cycle is completed or a specific condition is met, the timer triggers an audible alarm, such as a buzzer or bell, to notify personnel. This ensures that operators can take timely action, such as stopping a machine or checking a process.

Visual Signals

Function: Visual signals provide a clear, visual indication of the timer's status or the completion of a timing cycle. This can include lights or indicators that change color or flash.

Operation: Similar to audible alarms, visual signals are activated when a timing cycle ends or a specific condition is met. They are particularly useful in environments where noise levels are high, and audible alarms might not be heard clearly.

These features are critical in maintaining safety and ensuring that industrial processes are monitored effectively, allowing for quick responses to any changes or completions in the timing cycles.

What are the explosion-proof ratings of electromechanical timers?

Explosion-Proof Ratings of Electromechanical Timers

Electromechanical timers can be equipped with explosion-proof ratings, which are crucial for ensuring safety in hazardous industrial environments. Here are some key points about these ratings:

Purpose

Explosion-proof ratings are designed to prevent the ignition of explosive gases or dust that may be present in certain industrial settings. This is particularly important in industries such as chemical processing and mining, where the presence of flammable substances is common.

Design Features

Timers with explosion-proof ratings are constructed to contain any sparks or flames that might be generated within the device, preventing them from igniting the surrounding atmosphere. This involves using robust materials and specialized enclosures that can withstand internal explosions without allowing them to escape.

Applications

These timers are essential in environments where safety is a top priority due to the potential presence of explosive materials. They are used in applications such as chemical processing plants, mining operations, and other industrial settings where explosive atmospheres may occur.

Safety Assurance

By incorporating explosion-proof ratings, electromechanical timers help ensure that industrial processes can be carried out safely, reducing the risk of accidents and enhancing overall operational safety.

These features make explosion-proof electromechanical timers a reliable choice for maintaining safety in potentially hazardous environments.

What are the specific applications of explosion-proof electromechanical timers?

Specific Applications of Explosion-Proof Electromechanical Timers

Explosion-proof electromechanical timers are essential in various industrial applications where safety is a critical concern due to the presence of explosive gases or dust. Here are some specific applications:

Chemical Processing Plants

In chemical processing environments, explosion-proof timers are crucial for controlling processes that involve flammable substances. They ensure safe operation by preventing ignition sources in hazardous atmospheres, thereby reducing the risk of explosions.

Mining Operations

Mining environments often contain explosive gases and dust. Explosion-proof electromechanical timers are used to manage timing functions safely, ensuring that operations can continue without risking safety in potentially explosive conditions.

Oil and Gas Industry

In the oil and gas sector, where volatile compounds are frequently handled, explosion-proof timers are used to control equipment and processes. Their robust design helps prevent accidental ignitions, maintaining safety standards.

Manufacturing Facilities

In manufacturing settings where explosive materials are processed or stored, these timers help manage operations such as mixing or material handling, ensuring that timing functions do not introduce ignition risks.

Pharmaceutical Production

Pharmaceutical facilities that handle volatile chemicals use explosion-proof timers to control processes like mixing and reaction times, ensuring that safety is maintained throughout production cycles.

These applications demonstrate the importance of explosion-proof electromechanical timers in maintaining safety and operational efficiency in environments where potential hazards are present.

What are the differences between explosion-proof and non-explosion-proof electromechanical timers?

Differences Between Explosion-Proof and Non-Explosion-Proof Electromechanical Timers

Electromechanical timers can be categorized based on their safety features, particularly in terms of their ability to operate safely in hazardous environments. Here are the key differences between explosion-proof and non-explosion-proof electromechanical timers:

Explosion-Proof Timers

Design and Construction: Explosion-proof electromechanical timers are designed to prevent the ignition of explosive gases or dust present in certain industrial settings. They achieve this by containing any sparks or flames generated within the device, using robust materials and specialized enclosures that can withstand internal explosions without allowing them to escape.

Applications: These timers are essential in environments where safety is a top priority due to the potential presence of explosive materials. They are commonly used in chemical processing plants, mining operations, oil and gas industries, and other settings where explosive atmospheres may occur.

Safety Assurance: By incorporating explosion-proof ratings, these timers help ensure that industrial processes can be carried out safely, reducing the risk of accidents and enhancing overall operational safety.

Non-Explosion-Proof Timers

Design and Construction: Non-explosion-proof electromechanical timers do not have the specialized enclosures or materials required to contain internal explosions. They are suitable for use in environments where there is no risk of explosive gases or dust.

Applications: These timers are typically used in standard industrial settings where the risk of explosion is not a concern. They are suitable for controlling processes such as machinery operation, sequential operations in assembly lines, and fluid control systems where explosive atmospheres are not present.

Safety Features: While they may include other safety features like audible alarms and visual signals, they lack the specific design elements that make them safe for use in explosive environments.

These differences highlight the importance of selecting the appropriate type of electromechanical timer based on the specific safety requirements of the industrial environment in which they will be used.

Electromechanical Timers Media Gallery

References

Eagle-Signal Timer Selection

GlobalSpec—Digital Timers