[TheForge] Shop Lighting

[Grover Richardson]

Ahh.  You are sharp!!  And have the right idea<G>.

Ok, here's what is happening.  60 Hz or 60 cycles.  A full cycle is 360
degrees of operation.  A 120 Vac sine wave goes from 0 Volts to positive
169.7 Volts (120 Volts is rms, or root mean square, so the peak Voltage is
1.414 times the rms value), back through 0 Volts, down to minus 169.7 Volts,
and back to 0 Volts for a full 360 degrees of operation.  That is one cycle.

The important part is that the sine wave peaks twice.  And the fluorescent
bulb turns on twice for each "cycle" of power.  Once for the positive
portion and once for the negative portion.

For those who like additional information.  It takes a certain amount of
Voltage across a gas filled tube for the tube to turn on.  Then, when it
turns on, the Voltage drops to a value about 75% (generic here) of the turn
on Voltage.  The gas tries to maintain that Voltage drop across the gas no
matter what.  Physics, I don't remember why.  So, the ballast limits the
current through the bulb so that it doesn't burn up or pop the breaker.
When the Voltage drops below a certain value near that "on Voltage," the
bulb stops conducting.  Oh yes, when it conducts, it produces that light
effect that we like.  Only problem is that the light color that is produced
is not what we wish to see.  So the bulbs are lined with phosphors that take
the light and turn it into a light color that we do like.

The early regulator tubes (0A3, 0B2) were gas filled tubes and did the same
duty as zener diodes today.  But they were more sloppy in the regulation.
Every day in the Navy, I went to my power supplies and adjusted them for
proper Voltage, first thing.

Woof (I bark better than most dogs<G>)

Yes.  Faster than we can see.  As I remember it, film projectors flick at 24
frames per second.  Some people can barely perceive that.




>*>-----Original Message-----
>*>From: theforge-bounces at mailman.qth.net 
>*>[mailto:theforge-bounces at mailman.qth.net] On Behalf Of GHS
>*>Sent: Monday, February 27, 2006 3:47 PM
>*>To: Sponsored by ABANA
>*>Subject: Re: [TheForge] Shop Lighting
>*>
>*>
>*>Grover Richardson wrote:
>*>
>*>>
>*>>Actually 120 times, but that's ok<G>.  But yes, there are effects 
>*>>though we can't see them.
>*>>
>*>>  
>*>>
>*>If I had the time I'd build a strobe and check you out.
>*>As I remember it is OFF 60 times a second. It is also ON 60 times a 
>*>second. Thus the 120. I barely remember the explanation.
>*>
>*>Are the fluorescents essentially a DC operation? (Responding 
>*>to only one 
>*>half of the wave?)
>*> If so, I am correct.
>*> If not, you are.
>*>Never claimed to actually understand that stuff.
>*>
>*>Either way it is far faster than we perceive.
>*>
>*>Mike Graf
>*>
>*>-- 
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