Re: solux bulbs
Re: solux bulbs
- Subject: Re: solux bulbs
- From: "Bertho Boman" <email@hidden>
- Date: Wed, 13 Aug 2003 16:02:42 -0400
----- Original Message -----
From: "Roger Breton" <email@hidden>
>
>
Care to tell me more about that 'DC adjustable amd regulated supply'? And
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what CCT you're getting off the lamp? I've been looking for a way to nail
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down the exact conditions under which that lamp will actually operate at
>
4700K to advise my graphic design students in search for an affordable
color
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viewing environment.
The power supply that I am using is a 15 V 10 Amp switching power supply.
It is well regulated as are most regulated supplies today. Its output is
adjustable over about 12 to 16 volts.
The problem is that the two Solux bulbs that I have wired in parallel draw
more than 10 amps for a fraction of a second when turned on and the
powersupply has "foldback current limiting" which means that once an
overload has been detected, the current drops to a low value. It is so low
that the bulbs never light.
There are several solutions:
Use a powersupply that has just current limiting, not foldback.
Use a bigger supply.
Turn on one lamp first then the other one to reduce the startup spike.
Use a startup circuit.
.........
I use the last approach since I design electronics for a living and have all
the parts.
It is actually very simple: I placed a power resistor in series with the
bulbs on the output from the powersupply. It should be just about one ohm
or a little less. That will limit the current to below 10Amps. After a
fraction of a second, the filaments have warmed up and are very dimly lit
since the voltage is to low because of the resistor. I then have a 12 V
relay connected to short out the resistor to get full voltage to the bulbs.
It is all automatic since I connect the actuating relay coil across the
bulbs. When I turn on power, the voltage across the bulbs is very low and
the relay is not activated. As the filaments warm up, the voltage increases
until it is high enough to energize the relay which then closes and provide
full power. All this happens so quickly that it looks instantaneous.
Bertho Boman
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