Guide to Converting a Traditional Relay into a Time Delay Relay using a Timer Module

A conventional relay such as the one pictured in Figure 1 may be converted into a time delay relay using a timer module. In this example, 24 VDC Finder installed in a 90.02 socket is converted to a time delay relay by the addition of a timer module. The resulting system provides adjustable delays from 0.05 seconds to 100 hours.

Figure 1: This Finder 60 series DPDT relay may be converted into a time delay relay by the addition of the timer module. This timer module with its blue time adjustment screw is installed into the relay socket in the position normally reserved for the flyback diode.

Tech Tip: Manufacturer-provided catalogs remain an integral part of component selection. This is especially true when selecting green field components. Here the term green field refers to new installations unburdened by existing supply constraints. As a general rule, using components such as the timer module featured in this article allows a reduction in the total number of required components.

Focus on component families

Family relationships are one of the most important logistics considerations for industrial control components. Nearly all devices, from switches, relays, and even Programmable Logic Controllers (PLC) are offered as members of a greater family. We often find interchangeable components to facilitate customization for a given application. As an example, consider the relay components shown in Figure 2. Here we see members of the Finder 60 and 46 series. The timer plug-in module is designed to operate in either system.

Figure 2: Image of the Finder 60 series (left) and Finder 46 series (right). Both family members are compatible with the timer module (lower center).

Tech Tip: Don’t forget to include the relay locking mechanism. The octal socket on the left includes a wire retainer while the socket on the right includes a plastic locking mechanism that doubles as a relay ejection mechanism. This is another example supporting the need to review the manufacturers’ catalog.

Operation of the time delay module

The featured time delay module is simple to operate. There are two controls including the four dip switches to set the mode and coarse timing and a blue adjustment screw for fine time adjustments. For example, the mode may be set to time-delay-on and the coarse adjustment may be set for the 0.5 to 10 second mode. The screw visible in Figure 1 is then used to set the desired time interval within the 0.5 to 10 second window.

Parting thoughts

The time delay module is a simple device that can enhance the functionality of your control panel. It offers the advantage of consistency as a single family of relays may be used for both control and timing. Be sure to consult the device catalog to locate other family components such as jumpers, snubbers, and marker tags.

Please leave your comments and questions in the space below.

Best wishes,


P.S. Have you seen the DigiKey tech forum article on troubleshooting industrial equipment? This may be a good time to review the material. As you read the document, consider how the relay indicator LED may be used for symptom recognition. Hint: The timing module’s indicator LED is on while relay is active, not while the timer is counting.

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About this author

Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this. LinkedIn | Aaron Dahlen - Application Engineer - DigiKey