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From: "R. Lewis"
Newsgroups: sci.electronics.design
Subject: Re: LED Ballast
Date: Tue, 31 Dec 2002 19:46:19 -0000
Organization: Nextra UK
Message-ID:
References: <%AEP9.18271$Jb.8611@nwrddc02.gnilink.net> <20021229163639.06300.00000691@mb-fp.aol.com> <22MP9.19362$p_6.1519320@bgtnsc04-news.ops.worldnet.att.net> <026v0v84210mgiqhisarnsa9gf0gkuqlhe@4ax.com> <7c584d27.0212300417.3c83a9b4@posting.google.com>
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"John Woodgate" wrote in message
news:h2o97xAmrEE+EwG9@jmwa.demon.co.uk...
> I read in sci.electronics.design that Bill Sloman
> wrote (in <7c584d27.0212300417.3c83a9b4@posting.google.com>) about 'LED
> Ballast', on Mon, 30 Dec 2002:
>
> >John Woodgate may well find flaws in this superficially attractive
> >scheme, but it looks reasonably neat to me. Using a reactive impedance
> >for your current limiting reduces the heat dissipated in the ballast
> >from about 4.8W (20mA at 240V) to the 500mW you can dissipate in a
> >moderately cheap resistor.This would make construction a bit easier,
> >in that you don't have to worry about providing a low thermal
> >resistance heat path to ambient.
>
> I agree with the electronics, but there IS a safety problem. You CAN'T
> be sure that the LED will be connected to the neutral in all countries,
> because, for example, the widely-used Europlug and Schuko plug are
> reversible.
>
> If you use an 'LED indicator' *with a plastic body*, i.e. a holder
> similar to those used for panel indicators using filament lamps but
> fitted with an LED, you have extra protection and insulation normally
> sufficient to satisfy safety requirements.
> --
Don't forget to put a discharge R across the cap - else ouch! - let alone
the safety compliance issues.
Note then the working voltage of this R
How big a fuse will you require?
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