Simplest electromechanical relay circuit

[[email protected]]

It already has a crack in it by design, now about that Andreas fault.



You are doomed there, last night I was watching Mission Impossible Phantom Protocol,
where the guy was climbing on the outside to the 26th floor of such a building in Dubai.

Do not take all those high buildings the sun away?

In Dubai, is that a problem?

 

[Robert Baer]

You lost me.


You might want to re-think your feelings. I earned an electronics
merit badge in Boy Scouts over fourty-five years ago. I started
designing my own electronic circuits in junior high school. I started
taking EE classes after high school and my first job was with a
company that manufactured electronic medical devices (brain scanners).

Now, don't you feel silly? (You ought to even if you don't.)

The only reason I'm troubling myself to school you is that you offered
up a good suggestion in another followup. You more or less said told me
to look at the datasheet. Excellent advice!

Too bad that this datasheet lacks an example circuit, ergo my post.
http://datasheet.octopart.com/RP710024-Tyco-Electronics-datasheet-12624042.pdf

* Read "Coil resistance" in the Coil Data section (page one,top - where
it cannot be ignored or "lost").
The rest of it is symple Ohm's law to determine current, then power draw.

 

[Don Kuenz]

* Read "Coil resistance" in the Coil Data section ...
The rest of it is symple Ohm's law to determine current, then power draw.

Thank you for this and your earlier advice about what it takes to burnup
(melt the coil winding of) a relay.

###

Merry Christmas to all who read this!

--
__
__/ \
/ \__/
\__/ Don Kuenz
/ \__
\__/ \
\__/

 

[[email protected]]

Even if you're controlling one relay from another, it's not a bad idea to

have some sort of a snubber, to prevent the inductive kick back from the

controlled coil causing sparking at the contacts of the controlling relay

and wearing them out.



--

Tim Wescott

Control system and signal processing consulting

www.wescottdesign.com

Ummm, actually, not quite. If you read some of the peer reviewed literatureoutlining hardcore relay design details like contact materials, pressure and over travel, among many others, for DC relays anyway, relay life is actually improved by the redistribution of contact material by inductive flyback, tending to repair the erosion caused by the closure. Note the operative phrase is "is improved" and not "may be improved." Generally it is safe to say that if the relay is used within its inductive rating (or derating as the case may be) you can expect the full operational MTBF, however it is spec'd like 10,000 electrical actuations at full load, 1 million mechanical actuations, etc., without possibly making things *worse* with a snubber.

 

[Lasse Langwadt Christensen]

Den mandag den 23. december 2013 21.25.52 UTC+1 skrev John Larkin:

On a sunny day (Mon, 23 Dec 2013 08:55:55 -0800) it happened John Larkin

Oh, I know that.

Long long time ago I worked in a movie sound synchronization studio,

these used 'magnetocords', or perfotape audio recorders[1], the motors where

driven by a 3 phase net generated by coils from a generator

coupled to an electro motor that was braked somehow (forgot the details,

but the complexity was scaring).

The place was full of cabinets with nothing but relays.

Hundreds if not thousands of those.

And I had to keep it running.

[1]

That is audio tapes with holes in it like film, so it could be run in sync,

of course motors needed to be in sync too, also when speeding up from stopped.

Later I had to work as embedded and PC programmer with the Siemens PLC programmer guys

who used that ladder logic.

When I was a kid, a friend an I gave ourselves a tour of an old

strowger-relay telephone exchange. It was like a WWI battlefield in

there, rat-tat-tat noises in every direction.



The guys who worked there came across us and didn't seem to mind. They

showed us how some of the stuff worked, patch panels and battery rooms

and such.

The could probably tell just by the sound when a relay was worn and soon
needed replacement

I those days, we used to take the bus to the airport and knock on the

door of the control tower. They'd let us hang around and watch them

work, and look at the radars and stuff.



We used to wander into utility power plants, too.

They are probably all behind barbed wire fences now, We got guided tours
when I was in school

-Lasse

 

[[email protected]]

Um, no. You want to switch the *hot* side, not the neutral.

Nonsense, you can switch any side you want.

Ditto with fuse placement, "power switch", etc. Always interrupt

the *hot*, not the neutral.

Okay, that part is right.

 

[[email protected]]

With a suitable circuit, 24 V industrial relays can be reliably

operated from a 12 V car battery, provided that the switching cycle is

not too frequent to allow the capacitors in the circuit to recharge.

Ummm, that is not really true. The relay is designed so that it just operates at rated voltage and maximum temperature (50-85 oC range). The slack only exists at coil at room temperature, but most coils experience a temperature rise of 40oC in steady state. The minimum operate voltage therefore climbs at 3900ppm/oC, same as the copper winding.

 

[RosemontCrest]

Nonsense, you can switch any side you want.

While technically true (i.e. one *can*), it's safer to switch the hot
leg or both hot and neutral.

Okay, that part is right.

Did you not just contradict yourself?

 

[[email protected]]

While technically true (i.e. one *can*), it's safer to switch the hot

leg or both hot and neutral.

That is an unnecessary precaution for someone working inside the equipment who, if that reckless, is just as likely to touch the live stuff.

Did you not just contradict yourself?

No, the switch and fuse belong on the hot side.

 

[[email protected]]

On Sunday, December 22, 2013 1:48:56 PM UTC-5, Jim Thompson wrote:

Sounds like he's using an AC control relay with most of the current limiting due to the inductive reactance ( as a function of the armature being in or out), that's why it actuates at such a low voltage.

 

[RosemontCrest]

That is an unnecessary precaution for someone working inside the equipment who, if that reckless, is just as likely to touch the live stuff.



No, the switch and fuse belong on the hot side.

In this case, the relay acts as the "power switch." You agreed that the
switch should interrupt the hot leg. You contradicted yourself.

 

[[email protected]]

The issue is safety.



Joe Gwinn

I understand that but what does that have to do with relay contacts on the hot side? Is it a NEMA, NEC or UL requirement? If not, it's a non-issue.

 

[[email protected]]

In this case, the relay acts as the "power switch." You agreed that the

switch should interrupt the hot leg. You contradicted yourself.

I know enough to know that relays are not used that way without a manual disconnect. If you can't cite a regulatory requirement, there is no discussion here.

 

[RosemontCrest]

I know enough to know that relays are not used that way without a manual disconnect. If you can't cite a regulatory requirement, there is no discussion here.

My reply to you has nothing to do with regulatory requirements. You
stated that one can switch either hot or neutral leg, then in the same
post, you agreed that the hot leg should be switched. Regardless of any
regulatory requirements, you contradicted yourself.

 

[[email protected]]

My reply to you has nothing to do with regulatory requirements. You

stated that one can switch either hot or neutral leg, then in the same

post, you agreed that the hot leg should be switched. Regardless of any

regulatory requirements, you contradicted yourself.

Don Y's words were "Ditto with fuse placement, "power switch", etc. " No one refers to relay contacts as "power switch." Power switch means that gizmoid with ON/OFF labels that you work manually. Looks like it's remedial reading time for you.

 

[RosemontCrest]

Don Y's words were "Ditto with fuse placement, "power switch", etc. " No one refers to relay contacts as "power switch." Power switch means that gizmoid with ON/OFF labels that you work manually. Looks like it's remedial reading time for you.

Nice try, Fred.

 

[[email protected]]

It's certainly a NEC requirement, and most likely UL and NEMA as well.



Joe Gwinn

I checked NEC and it definitely is NOT a requirement.

 

[[email protected]]

You don't much about relays, you don't know anything about compliance, all you're here to do is promulgate a bunch of anecdotal mythology.

 

[RosemontCrest]

You don't much about relays, you don't know anything about compliance, all you're here to do is promulgate a bunch of anecdotal mythology.

I am not the only one posting to this thread who disagrees with you. I
notice that recently you have been ridiculed by others in different
threads within this newsgroup. Have you considered the possibility that
there may be a common denominator?

 

[[email protected]]

Science and engineering are not a democracy. You're a pathetic little idiotnothing of a person to fall back on that puny non-justification, and you're too dumb to realize just how idiotic you look to anyone with a working knowledge of the technology. Imbeciles like you make the internet the trash heap of misinformation, ignorance and mediocrity it is today. The bottom line is you don't know what you're talking about. STFU and go away.