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From: "Phil Allison"
Newsgroups: comp.home.automation,sci.electronics.design
References: <20021202011023.25141.qmail@nym.alias.net> <20021202133025.25029.qmail@nym.alias.net> <3DEB8034.5010402@nospam.com> <20021203025106.27096.qmail@nym.alias.net> <3DECCCDF.1000806@nospam.com> <3DED7F7E.7070000@nospam.com> <3DED8361.8090706@nospam.com>
Subject: Re: Triac controlled holiday lights
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Date: Wed, 4 Dec 2002 16:14:33 +1100
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"Fred Bloggs" wrote in message
news:3DED8361.8090706@nospam.com...
>
>
> Phil Allison wrote:
> > "Fred Bloggs" wrote in message
> > news:3DED7F7E.7070000@nospam.com...
> >
> >>
> >>Phil Allison wrote:
> >>
> >>>"Fred Bloggs" wrote in message
> >>>news:3DECCCDF.1000806@nospam.com...
> >>>
> >>>
> >>>
> >>>
> >>>>Right- but those were for bulbs rated for 120VAC. The half-wave
> >>>>rectification cuts the RMS down to 70% of that or 84VAC. In your case,
> >>>>you would have 84VAC across a string rated for 60VAC, and this will be
> >>>>bad news. My dimensions were off in the original post, but if the
bulbs
> >>>>are rated at 700 hours on 60VAC, then 84VAC will reduce their lifetime
> >>>>to 12 hours.
> >>>
> >>>
> >>>
> >>>
> >>> ** No, much less than that with a 40% overvoltage.
> >>>
> >>> The 2 to the power of 12 rule is only valid for small
voltage
> >>>deviations.
> >>>
> >>> You must have missed that one at Uni Fred.
> >>>
> >>>
> >>
> >>It is not a 2^12 rule, it is the (voltage ratio)^12 rule, and in this
> >>instance it is good for concluding with great confidence that 84Vrms is
> >>way out of bounds.
> >
> >
> >
> >
> > ** Then you should have posted *that* and not the erroneous figure
you
> > did.
> >
> >
>
> It's called a *persuasion estimate*- no point in exactitude to the
> pointlessness of absurdity.
** It was an error - the formula does not apply, admit it Fred.
Others read this stuff and learn or mislearn as the case may be.
.................. Phil
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