Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering magazine articles Engineering software Engineering smorgasbord RF Cafe Archives RF Cascade Workbook 2018 RF Symbols for Visio - Word Advertising RF Cafe Forums Magazine USAF Radr Shop Sponsor RF Cafe RF Electronics Symbols for Visio RF Electronics Symbols for Office Word RF Electronics Stencils for Visio Thank you for visiting RF Cafe!
Axiom Test Equipment - RF Cafe
ConductRF Phased Matched RF Cables - RF Cafe

About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024


    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:


Berkeley Nucleonics Phase Noise Testing Seminar - RF Cafe

Finding Relay Operate and Release Times
April 1967 Electronics World

April 1967 Electronics World

April 1967 Electronics World Cover - RF Cafe  Table of Contents 

Wax nostalgic about and learn from the history of early electronics. See articles from Electronics World, published May 1959 - December 1971. All copyrights hereby acknowledged.

Sometimes, component datasheets can be pathetically lacking in detail for parameters that you might think would be a minimum amount of information needed in order to integrate the device into a circuit or system. Or, it may be that you found a part in a spare parts box and can't find a datasheet for it. When those times come, it is necessary to characterize the part yourself. Relay control really isn't rocket science when it comes to electrical circuits, but there are a few rules of thumb that should always be observed, the most important of which (other than not exceeding voltage and current maximums) is to wire a diode reverse biased across the coil terminals so that the voltage/current induced due to the field collapse during de-energizing does not smoke the driver circuit.

This article from the April 1967 edition of Electronic World magazine recommends a test setup for determining the cut-in and cut-out speeds. It might be important to know the speed in case the application has a timing requirement for synchronization with another part of the circuit/system.

Here are links to the other relay articles:  Operate and Release Times of RelaysReed RelaysTime-Delay RelaysFinding Relay Operate and Release TimesArc, Surge, and Noise Suppression

Finding Relay Operate and Release Times

By Donald Ludwig

Circuit used to find operate time of relay along with oscilloscope display - RF Cafe

Fig. 1 - Circuit used to find operate time of relay along with oscilloscope display that is produced with setup.

Circuit used to find release time of relay - RF Cafe

Fig. 2 - Circuit used to find release time of relay. The values of CLR and Vc depend on particular application.

When designing circuits using relays it is often necessary to know the relay's operate and release times. Because of certain circuit conditions, the times given by the manufacturer will not always hold true. The method to be described will help establish these parameters and requires only a regulated power supply, a single-trace oscilloscope, and two simple circuits - as suggested by the National Association of Relay Manufacturers. This article illustrates the standard s.p.d.t. break, make Type-C relay under test. This type of relay is frequently used and the circuits employed can easily be converted to test other types of relays.

Operate time begins when the energizing voltage is applied to the relay coil and ends when the wiper arm has reached the energized (N.C.) position. See Fig. 1. Release time starts with the removal of the energizing voltage from the coil and ends when the wiper arm has returned to the de-energized (N.C.) position. See Fig. 2.

The checks should be made under conditions closely approximating actual operating conditions. These include temperature, mounting position, use of arc suppressors, and any other circuit conditions that may affect operate and release times. It should also be remembered that the accuracy of the test is dependent on the accuracy of the scope, if all other precautions are taken.

If the relay being tested has more than one set of contacts, the operate and release times of each set being used should be checked. The time required for each set of contacts to function may differ from one set to another. An increase in coil temperature due to repeated operations of the relay may cause the resistance of the coil to change and affect the time elements of the relay. Each set of contacts should be checked several times before calling the test conclusive.

When determining relay operate and release times, the scope's sweep speed should be set with a time base which will permit viewing of the waveforms and still allow accurate readings to be made.

This method requires no elaborate equipment to establish the relay's operate and release times. Using an oscilloscope also permits contact bounce to be examined.



Posted November 25, 2019(original 2/12/2012)

RF Superstore (RF Components) - RF Cafe
RF Cafe Sponsors
RF Electronics Shapes, Stencils for Office, Visio by RF Cafe
Anatech Electronics (RF Filters) - RF Cafe

Please Support RF Cafe by purchasing my  ridiculously low−priced products, all of which I created.

These Are Available for Free