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12 volt fluorescents


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#1 Matt Sandstrom

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Posted 05 December 2005 - 04:54 PM

hey, i'm thinking of building my own fixture for a ringlight tube and i was just wondering whether all 12 volt ballasts are flicker free. i can't see why they wouldn't since they operate on dc power and can create any frequency they like, and since higher is better for a number of reasons... the problem is just that the cheap ballasts i'm looking at don't specify anything of this so how can i tell?

thanks,
/matt
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#2 Phil Rhodes

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Posted 05 December 2005 - 07:45 PM

Hi,

I have never seen one that isn't, but I'd still check.

Phil
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#3 Michael Collier

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Posted 05 December 2005 - 08:20 PM

Just cause they can modulate high frequncys, doesnt mean they would. High frequency is made more ineffient the greater the load that is applied (inductions a pain unless your talking about the coil in your car) so they may scale the freq down to save battery power. Remember, their goal was effiecient flicker free (to the eye) use, not scaled to film or video use. test it. its cheap anyways

FYI, i used a lamp that was a plug-in unit, but used a wallwart to convert to 12vdc, and an internal ballast to drive the light. Using a HVR-ZU1 (sony) at 30i cine frame mode I did not detect any flickering or phase shift.
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#4 Phil Rhodes

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Posted 06 December 2005 - 08:00 AM

Hi,

Usually, 12V fluorescent tube drivers (which can't really be called ballasts in the same sense as a mains one) are designed around a ringing-choke arrangement, which oscillates at the resonant frequency of the inductor. For any practical inductor in those circumstances, that will be many kilohertz. I'm talking here about the handheld fluorescent flashlights, boat/trailer lighting units, and battery-backed emergency exit signs, that kind of thing. Watch Aliens, where Lance Henriksen's character carries a combination incandescent/fluorescent torch for some of the opening scenes on the planet. That'll be one of those.

Phil
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#5 Matt Sandstrom

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Posted 06 December 2005 - 02:01 PM

thanks guys. i'll let you know how it goes.

/matt
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