LED as power on indicator with AC Mains Supply

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peterlonz
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Re: LED as power on indicator with AC Mains Supply

Post by peterlonz » Wed Feb 17, 2010 3:08 pm

OK Guys,
Transformers are yesterdays solution to this specific problem.
AFAIK no power strip manufacturer employs that approach.
Why? Mainly cost, but also bulk, & difficulty in mounting.

Am I pushing things in terms of current demand?
In the judgment of a conservative technician, perhaps.
In my judgement, no.
In the judgement of your average non-tech user, NO.
I'll explain; In my experience it's not unusual to have folk mention that they have certain circuits in their homes, that are prone to overload tripping of the main switchboard circuit breakers (this includes some new homes).
Most often its the laundry where a drier, washing machine & iron might be simultaneously in use. What do they do, just be careful because the trip out is a nuisance.
Similarly I know of folk who have 6-way & 8-way power strips crammed with leads to various appliances who confide that they sometimes trip the protection mcb. They realise they are pushing things & generally just exercise more care because the trip out device takes some time to cool & allow a reset.
That's the real world at least as I see it.
I am sure however this is a long way from the set up in any electrical technicians home!
My mains circuit is 15A rated.
My power strip is 10A rated.
Until this particular power strip suffered a component failure, probably surge related, (remember the mcb did not trip) I had encountered zero problems over a 5 year period. Now that does not sound like a marginal application to me.

Regarding power strip design generally; it looks to me as though some manufacturers have solved the technical problems of indication, surge protection & overload protection quite well. Otherwise I am sure we would all be aware of "power strip issues".
Contributors to this tread have made some great suggestions: splitting into a seperate unit the control unit, indicating power on, off, off with alarm, & "on+on".
If this was a mission critical application I'd be encouraged to follow such lines maybe.
OTOH, if I accept that a small chest freezer is only "sort of" mission critical, then my simplest remedy is to buy a power strip with indication & overload protection only, or better yet overload protection only.
Regarding fire risk, I suspect this is over stated, all the power strips employing an internal circuit board, to offer more sophisticated features, potentially have failure prone components that can short. They appear however not to be considered as fire risks, is this due to the mounting or that fires are in practice very rarely started in this way.
I don't know how many are fused, but since a fuse failure would mean for most folk a replacement unit was required, a conventional fuse does not add much other than an extra component.
How "safe is Mr Al's solution" I recall he specified a fuse but I am unsure what would happen if the fuse was omitted.
Peter O

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CeaSaR
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Re: LED as power on indicator with AC Mains Supply

Post by CeaSaR » Wed Feb 17, 2010 3:33 pm

Well, I did say that MrAl's setup looks very promising. I'd be inclined to trust it as he has shown himself to be
very thoughful/considerate in his design (of many years :smile: ). As an old school (still neophyte) person, I'm used
to the older tech and the fact that the old stuff tends to last alot longer/is alot more reliable than the newer/
cheaper stuff. As for whether or not the power to a chest freezer is mission critical, well, is the possibility of loosing
several hundred AU dollars mission critical? Maybe, maybe not. If your initial post is any indication, you think it is. My
suggestion of an indicator for mains power and outlet power is a quick visual to let you know the status of both. If
the outlet LED is out, it is either the circuit failed or the outlet died. If only the mains LED is out, you know that circuit
has failed, but power is still on to the outlet/plugged in device. If both are out, you know to check the mains. Either
way, you can get several days out of a closed chest freezer before real problems set in.

CeaSaR
Hey, what do I know?

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sofaspud
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Re: LED as power on indicator with AC Mains Supply

Post by sofaspud » Wed Feb 17, 2010 3:56 pm

Am I pushing things in terms of current demand?
In the judgment of a conservative technician, perhaps.
In my judgement, no.
In the judgement of your average non-tech user, NO.
-and-
My mains circuit is 15A rated.
My power strip is 10A rated.
It's not really about judgement.
Half the information is in the second quote. The other half is the current draw when food is cooling,
batteries are charging, and clothes are drying. Then it becomes a factual matter. As it should be.
As a "conservative technician", that's how I like it.
Tripping protection circuits is being more careful? I live in a different world, bro.

peterlonz
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Re: LED as power on indicator with AC Mains Supply

Post by peterlonz » Wed Feb 17, 2010 11:17 pm

Sofaspud,
Thanks for your comment throughout the thread posts.
Actually I never intended my comments should be interpreted to mean that I am happy to trip protection circuits about which I feel as you do.
I merely said (words to the effect) that this sort of thing happens with some frequency in homes round the world.
Actually in my home I have never had an overload protection circuit trip.
The RCD did trip once when my wife allowed a cable powering a hedge cutter to fall into the pool, that did not happen again.

I think the best of what can be said & learned has already been said now.
Again I thank everyone who posted for their contribution to my understanding & general knowledge on this subject & particularly Mr Al whose know-how seems legendary.

Peter O

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sofaspud
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Re: LED as power on indicator with AC Mains Supply

Post by sofaspud » Fri Feb 19, 2010 5:33 pm

Sorry for the misunderstanding. I appreciate the clarification.
And I too am confident MrAl would not foist some half vast boondoggle on the group. I just wanted you to be aware of precautions
and shortcomings. I'm dissatisfied with the shortcomings of all the suggestions, including my own (i.e. paralleled "sensor"). But life
goes on whether it's electronics conclusions or sociological conclusions. Best of luck with your project, mate.

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