electrical relays

[kenmbz]

Then you could open a radio shack, oh wait, that's been done

 

[k0ua]

Just because it is cold and snowing outside, and I don't have much to do, I thought I would go on an informative tirade one more time to help describe the "why" of relays. There still seems to be some lingering lack of understanding why these things are so darn useful. This is going to be a "book" so if you don't like to read, now would be a good time to skip on to the next topic.

One of the things I like to do to illustrate my point is to "go big" on explanations. So I am going to use a "big" example of relay control.

Lets say you are the lock keeper down at the panama canal. You are sitting up in a control tower some distance from the actual lock that you are going to open and close. Now these locks weigh weigh many tons and are driven by motors of thousands of horsepower that power gear systems that actually swing the gates of the lock themselves. What I am trying to describe here is huge motors, huge gear trains, huge doors. These motors require huge voltages and currents to operate.

But in front of the lock keeper is a console with a a little switch on it that says open and closed. From that tiny switch is a few hundred yards of small wire that goes out to the control room where all of those huge motors are located.

The question is how is this tiny switch and those tiny wires going to control those huge motors located so far away?

Of course some of you don't even see a problem at all. Your bliss derives from a lack of knowledge of Ohms law. Byt others are starting to have some doubts about that tiny switch and those long tiny wires being able to control such a huge load. And as well you should.

Enter the concept of the relay. A device that can be actuated by a small voltage and small current and can control large voltages and large currents. Or in this case we are probably talking about relay's controlling even larger relays and likely many of them.

So you see the guy up in the controller is just controlling a much larger chain of events when he flicks his little switch to say "open". And it would not matter if he was hundreds of miles or even thousands of miles away. He could still control the huge chain of events to make those huge doors swing open. Such is the magic of the relay. A device that spans distance and a huge amount of power.

I hope this absurd little dissertation broaden the outlook of some and made you think a little. And the world would be a different place if someone didn't come up with the idea of a relay.

 

[kenmbz]

Next on to resonance and IC timers
K0UA - your description is great and I might use it with my son, better than the dry talk about current or voltage amplification.
I wonder how many people know that relays were used as switching devices for phones and computers and how they eventually got replaced by tubes, and then transistors.

 

[the old grind]

Just another three terminal relay.

https://i2.wp.com/www.easycarelectrics.com/wp-content/uploads/2021/06/Starter-Solenoid-Wiring-Diagram.jpg?fit=700,647&ssl=1

 

[IndyJay]

Just because it is cold and snowing outside, and I don't have much to do, I thought I would go on an informative tirade one more time to help describe the "why" of relays. There still seems to be some lingering lack of understanding why these things are so darn useful. This is going to be a "book" so if you don't like to read, now would be a good time to skip on to the next topic.

One of the things I like to do to illustrate my point is to "go big" on explanations. So I am going to use a "big" example of relay control.

Lets say you are the lock keeper down at the panama canal. You are sitting up in a control tower some distance from the actual lock that you are going to open and close. Now these locks weigh weigh many tons and are driven by motors of thousands of horsepower that power gear systems that actually swing the gates of the lock themselves. What I am trying to describe here is huge motors, huge gear trains, huge doors. These motors require huge voltages and currents to operate.

But in front of the lock keeper is a console with a a little switch on it that says open and closed. From that tiny switch is a few hundred yards of small wire that goes out to the control room where all of those huge motors are located.

The question is how is this tiny switch and those tiny wires going to control those huge motors located so far away?

Of course some of you don't even see a problem at all. Your bliss derives from a lack of knowledge of Ohms law. Byt others are starting to have some doubts about that tiny switch and those long tiny wires being able to control such a huge load. And as well you should.

Enter the concept of the relay. A device that can be actuated by a small voltage and small current and can control large voltages and large currents. Or in this case we are probably talking about relay's controlling even larger relays and likely many of them.

So you see the guy up in the controller is just controlling a much larger chain of events when he flicks his little switch to say "open". And it would not matter if he was hundreds of miles or even thousands of miles away. He could still control the huge chain of events to make those huge doors swing open. Such is the magic of the relay. A device that spans distance and a huge amount of power.

I hope this absurd little dissertation broaden the outlook of some and made you think a little. And the world would be a different place if someone didn't come up with the idea of a relay.

The older among us may remember when our headlight dimmer switch was on the floorboard, left of the clutch pedal. It made a real loud "thunk" when you pressed it with your foot. Nowadays the headlight dimmer is on a little tiny stem on the steering column and it is a tiny "click". The old high current foot switch has been replaced with the tiny switch on the steering column and a relay.

Not as exciting as the canal example that James used above, but you don't have to worry about getting a cargo ship stuck sideways in it.

 

[LittleBill21]

relay testers are common in automotive. surprised people haven't seen them

Amazon.com

www.amazon.com

 

[the old grind]

Alligator clips are a lot cheaper and pinouts are never a secret. A relay doesn't cost much more with a socket and pigtail. (u only need one) Wouldn't take much then for a guy to test with a $6 VOM from HFT and jumper from a battery to energize.

I bet somewhere there's a light bulb tester, too.

 

[LittleBill21]

Alligator clips are a lot cheaper and pinouts are never a secret. A relay doesn't cost much more with a socket and pigtail. (u only need one) Wouldn't take much then for a guy to test with a $6 VOM from HFT and jumper from a battery to energize.

I bet somewhere there's a light bulb tester, too.

Testers like i linked save time for people who do it for a living.. you can also use a light bulb in place a of a multimeter, I will still own a multimeter...

 

[koshari]

This seems silly to me. You close the switch to energize the coil and closes the contact which then supplies voltage to the load. Why not just have the switch in place the the relay contact? Hmmmmm, I'm sure there must be a reason but it escapes me at this time.

Because you can bank them up without overloading the switch as the only current the switch provides is picking up the coil.

 

[LittleBill21]

Because you can bank them up without overloading the switch.

also significantly smaller wire and cheaper switch.