Timer Relays

Timer relays are control devices that combine an electromechanical relay with a built-in timing function, allowing circuits to be switched on or off after a pre-set delay. Unlike standard relays, which operate immediately when a voltage is applied or removed, timer relays are designed to delay switching actions by a specified interval — from milliseconds to several hours or even days.

These relays are commonly used to automate sequential operations in industrial and electrical systems. They are available with normally open (NO) or normally closed (NC) contacts and offer various timing functions such as delay-on, delay-off, interval, and cyclic timing. When choosing a timer relay, it's important to consider the type of delay required and the demands of your specific application. 

Types of Timer Relays

When designing your application, it is important to understand the difference between the types of the Timer Delay Relays, considering what should initiate the delay and if it should start at the same time as the application, as well as when the voltage is released. Timer Relays are triggered/initiated by either Voltage being applied or the closing or opening of a trigger signal.  

The most common timing function of Delay Relay are:

• On Delay - The timer starts when voltage is applied. After the set time has elapsed, the relay activates.
• Off Delay - The relay is triggered when voltage is removed, remaining active for a set time before switching off.
• Single Shot (One Shot) - A brief trigger signal causes the relay to activate for a single timed interval.
• Interval (Interval On) - The relay turns on immediately when triggered, stays on for the set time, then turns off.
• Flasher (On-First / Off-First) - The relay alternates between on and off states repeatedly at a fixed interval.
• Repeat Cycle - The relay repeatedly cycles on and off whilst power is applied, useful for pulsing control systems.

Applications of Timer Relays

Timer relays are commonly used in industrial automation and OEM equipment, particularly where precise timing control is required in control panels or sub-panels. They play a key role in sequencing, delay, and timed safety operations.

Typical applications include: 

• Lighting circuits with automatic on/off timing
• Motor start control and sequencing
• Delay functions for sensitive equipment start-up
• Safety interlock systems
• Conveyor belt sequencing and delay shutdown

At RS, we offer an extensive selection of timer relays and related products from leading brands such as Omron, Allen Bradley, ABB, and Schneider Electric. Our range includes single-function and multi-function timer relays, accessories, and solutions for industrial automation and control.

Discover products from ABB and many more, all available with Next Day Delivery to keep your projects on schedule.

To learn more about relays and their applications, take a look at our expert-reviewed Relays Guide.