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From: "R. Lewis"
Subject: Re: LED Ballast
Date: Tue, 31 Dec 2002 19:46:19 -0000
Organization: Nextra UK
References: <%AEP9.18271$Jb.email@example.com> <firstname.lastname@example.org> <22MP9.email@example.com> <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: Tue, 31 Dec 2002 20:05:12 +0000 (UTC)
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
"John Woodgate" wrote in message
> I read in sci.electronics.design that Bill Sloman
> wrote (in <firstname.lastname@example.org>) 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
> 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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