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From: "R. Lewis"
Subject: Re: 12V Fluorescent lamp driver
Date: Fri, 1 Nov 2002 19:15:03 -0000
Organization: Nextra UK
NNTP-Posting-Date: Fri, 1 Nov 2002 19:14:33 +0000 (UTC)
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
"N. Thornton" wrote in message
> "R. Lewis" wrote in message
> > "N. Thornton" wrote
> > > email@example.com (Dave H) wrote in message
> > > > I'm planning to build a circuit to drive a Compact fluorescent lamp
> > > > from a 12v car battery for use in a garden shed. The circuit wants
> > > > be as cheap/reliable as poss and preferably use off the shelf
> > > > components.
> > > >
> > > > I was thinking along the lines of a simple oscillator (running at
> > > > roughly 50hz) driving something like a 2N3055 connected to the
> > > > secondary of a mains transformer.
> > > >
> > > > Is there a better way?
> > >
> > >
> > > Sounds perfectly effective. Yes there are ways better in some
> > > respects, but what is wanted is simplicity, ease of building and low
> > > cost. Your solution fits the bill.
> > >
> > > I would be temted to use a higher frequency, maybe a few hundred Hz.
> > > And your invertor will have no regulation, and a 12v batt swings ovre
> > > a wide V range. So I would add tap switching to select the nearrest
> > > voltage - otherwise your V will be miles out at times.
> > >
> > If you use 'a few hundred Hz' what ballast can be used?
> > Discharge tubes, such as fluorescent tubes, have a negative resistance
> > must be 'ballasted' in some way.
> > Typically from low voltage DC, fluo' tubes are powered by a Hartley or
> > type inverter at frequencies in the tens of kHz.
> > The output of the inverter (transformer) , although it has a high(ish)
> > impedance, generally requires ballasting - which is normally achieved
> > cap.
> > Unless you are familiar with such things they can be tricky.
> > If you go down the mains frequency/volts route be aware that some, but
> > all, mains ballasts ('chokes') are far from happy with square waves.
> > In the interest of efficiency you may want to power factor correct your
> > mains ballast set-up.
> Dave is running a CFL, not a FL. They should run just as well off
> 300Hz as 50Hz.
> But I think the suggestion to get a 12v CFL has to be the most
> sensible. Personally I would be more into running mains power to the
> shed, that would be far more useful.
> Regards, NT
What is meant here by a compact fluo' tube?
Any fluo' tube that is folded may be described as a compact fluo tube. Some
small ones have integral HF ballasts others - 55W 2D for example - do not.
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