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Investigating a Relay – Experiment 7

For those of you who have missed my previous six blog posts, I recently got the second edition of “Make: Electronics” by Charles Platt and decided to try all of the experiments presented in the book. This is my documentation of how the seventh experiment turned out.

Time to re-lay the groundwork for all of our subsequent experiments!

CAUTION: This experiment involves the use of a utility knife. We advise our young readers to ask an adult for help or stick to looking at the pictures of the inside of the relay included in this article and the book.

The Relay

The “Necessary Items for Chapter Two” section, at the beginning of chapter two of the book recommends some relay models with the same pin functions as the one used by Mr. Platt.

One of them is the Omron G5V-2-H1 DC9 (Figure 2-20 of the book). You are also to use a relay that does not require polarity and is non-latching.

But, how can you find out if your relay has these specs? You check the datasheet!

The Omron G5V-2-H1 DC9, for example, has the Digi-Key part number Z3673-ND.

You can see the relay’s specifications on the Product Attributes table on the lower section of the part detail page. The “Coil Type” is specified as “Non Latching”, which is what we want.

To check the coil polarity we should check the relay’s datasheet.

Page 4 shows the dimensions and terminal arrangement of the relay. The pin spacing and internal connections of the relay match those from Figure 2-21 of the book.

Below, the “Bottom View” of the “Terminal Arrangement/Internal Connections” you see between parentheses that there is “No coil polarity”.

(Image source: Omron)
So the Omron G5V-2-H1 DC9 matches all of our requirements!

Test Yourself! Look for the datasheets of the other relays recommended by Mr. Platt and confirm they match the specifications required.

Procedure

Don’t confuse the faint click of the relay with the click of the pushbutton.

Touch the relay’s body if needed, so you can “feel the click” when you press the pushbutton and the contacts in the relay open and close.

Testing the continuity between two contacts

It was tricky to hold the multimeter’s probes against the relay’s contacts while trying to press the pushbutton, which is why I used test leads as shown in Figure 2-51 of the book.

Test the continuity between several contacts both when pressing and not pressing the pushbutton.

How about measuring the continuity between the contacts on different sides of the relay, are they ever connected?

If you don’t know how to measure conductivity with your multimeter be sure to check its manual. If your multimeter is the EXTECH EX330 from FLIR, set you meter’s dial to measure continuity and then click the MODE button several times until you see the continuity symbol on the multimeter’s screen.

Testing for Conductivity:

Here are my results!

But what about testing the conductivity between the contacts on the left and right sides of the relay?

Feel free to try, but there’s no conductivity whatsoever between the left and right sides of the relay.

To understand why, read the “What’s Going On Inside” and “Other Relays” sections of the experiment. Can you now better understand how your relay works? There’s no conductivity between the left and right contacts of the relay because they’re two different poles!

Opening It Up

CAUTION: This part of the experiment involves the use of a utility knife. We advise our young readers to ask an adult for help or stick to looking at the pictures of the inside of the relay included in this article and the book.

Be sure to always move the knife away from you. Work slowly and be patient.
It’s not a sprint, if you get tired, ask for help and make it a relay! ☺

Don’t shave the edges of the plastic shell any more than you have to, so you can continue using this relay in later experiments.

Connect the relay again, this time, when you press the pushbutton and current passes through the coil, you will be able to see the insides of the relay moving.

Lastly, read the “Fundamentals: Relay Terminology” section of the experiment.

Practice looking for the all the terms introduced in this section of the book by looking at the Omron G5V-2-H1 DC9 Digi-Key part detail page and the relay’s datasheet.

Hint: The switching capacity is specified for a resistive load.

Learning how to find components with the right specifications is an essential skill that will help you save time and money as you move forward with your learning.

EXTRAS

If you would like to learn more about relays, this YouTube video is very informative: GreatScott! - Electronic Basics #32: Relays & Optocouplers

If you just want to read about relays, see Encyclopedia of Electronic Components Vol. 1, Chapter 9 “Relay”.

Finally, if you would like to try this experiment yourself, you can get everything you need from Digi-Key!

About this author

Savitri Sepulveda, Associate Applications Engineering Technician, started her career at Digi-Key Electronics in 2017. She is responsible for helping European customers resolve their technical questions. Savitri holds a Bachelor of Science degree in Industrial Engineering. In her free time, she likes to tinker with electronics, volunteer as an English teacher at the local Senior Center, play video games and take MOOC courses.

More posts by Savitri Sepulveda