Simplest electromechanical relay circuit

NEC is authored by NFPA, founded a little over a hundred years ago. It's fundamentally a fire prevention code. Accident prevention is achieved by grounding and that's about it.

You are certainly correct. Bloggs, as usual, doesn't know what he's talking about.

You couldn't rewire a house lamp...then we already know you don't know how to screw a bulb in it after you get through screwing up the wiring.

You lefties always lie. You're incapable of anything else. You're too stupid to use a real newsreader/server, as well. You really are as dumb as Slowman.

yes, above unity power gain implies acive.

NFPA certainly cares about fires, and we continue to have electrical fires.

Grounding is certainly important, but there is far more to it than that. No single method is complete, so one uses multiple methods in parallel, so all methods must simultaneously fail for there to be a problem.

Joe Gwinn

An entry for "active device" is missing from my _IEEE Standard Dictionary_. _The Art of Electronics_ mentions, in passing, "The transistor is our most important example of an 'active' component." That's it. My textbooks also contain no definition so it seems that one must use the Inet to find a working definition.

An active device is any type of circuit component with the ability to electrically control electron flow (electricity controlling electricity).

A relay certainly controls electron flow as much as a transistor switch. As mentioned previously, _The Art_ says that a transistor is an active component. Ergo, my vote on the matter is also, "Yes." :)

The simpler the question, the longer the tread.

Geez, really? The installed wiring base spans at least 90 years so, unless there is a requirement for retrofit, don't expect an abrupt decrease in frequency.

Thank you. Your example suggests that instead of "not *really* the best," it is "not *always* the best."

relay

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That is not really the best. There are special cases (Classified locations and some specific safety equipment relating to classified locations) where switching neutral is correct, but generally it is not the best idea. See NEC article 500 et seq.

?-)

Low side switching is very common but it usually does not leave the safety zone. For example, inside an industrial control cabinet and integrated reversing relays that passes the neutral of a pair of coils through an overload contact.

Other examples where you may need various voltages to be switched from a single triac output module array. Those would have it's common leg tied to neutral and all the devices coming to each triac output would be alive at all times with their required voltages, 24, 48, 115, 230, 480 AC. Etc.

Jamie

I know what *I* think 'active' means, but I would like to know what practising EEs think.

By a narrow margin I think that you are a "yes".

Indeed! These are the reasons for my question.

Thanks for this. Unfortunately they go on:

'for a circuit to be properly called electronic, it must contain at least one active device.'

and I disagree!

is worth reading. It complicates the topic, but there are some good points on the Talk page.

I would say so too, FWIW; others would demur.

I will start another thread rather than hijack yours.

There is some uncertainty about the meaning of 'active'.

Ah! I hadn't thought of those. Lasers & masers too, I suppose. The essence is "power gain", so they probably need not be electronic.

I will start a new thread.

Cheers!

Wasn't there a "rule of thumb" for voltage rating relays yourself? I seem to recall 1.5 times the voltage that barely actuates it, but it could have been double just for reliability. How did they figure the top end of the voltage range? I seem to recall some relays marked with resistance and a current but no voltage specified.

Carson's "High Frequency Amplifiers" (great RF book btw) defines an active circuit as one that can amplify power or oscillate continuously.

Active vs. passive is a property of a circuit, rather than just a device. It's usually defined in a small signal context, or at least referring to small perturbations around a steady state situation (as in a class-C amplifier). A given device operated at a given bias can easily be active at one frequency and passive at another.

"Active device" is a much vaguer term, IIUC, and means something like "a device capable of amplifying or oscillating under some circuit conditions". I normally think of this in small-signal terms, so I'd say that a relay is passive, but other folks will probably point out that it's easy to make a relay oscillate by having it switch its own coil, like a buzzer, or to switch some much larger signal.

Cheers

Phil Hobbs

A bit less than what melts it? *

(*) or degrades plastic parts too quickly etc at max rated ambient temperature