Re: UV Article

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From: Sandy King (sanking@clemson.edu)
Date: 12/10/01-01:51:51 PM Z


Don,

  As I understand you are using a bare wire ground to each of the
tubes in place of the grounded metal beneath the bulbs? I assume this
wire is then joined to the common point that ties the ballast and
other metal parts of the fixture?

For sure the ballast needs to be grounded. With two-tube holders that
is already taken care of, provided of course that you tie the rest of
the unit to a common ground.

Sandy King

>
>As Linas pointed out in an earlier e-mail the ballasts need to be
>grounded. When I built my UV printer, I simply extended a bare
>ground wire that touched the top of each tube (12 20w BLs). This
>provides for an unobtrusive and safe way to let the bulbs "see"
>ground to allow for easy startup and no flickering. In addition I
>painted the inside of the enclosure a flat white to allow maximum
>reflectivity without creating a specular diffuse light source like
>you may get with say crumbled aluminum foil or unpainted metal
>surfaces.
>
>Please note that you will need to be certain that the AC wiring from
>your wall outlet is correctly polarized.
>Polarity checkers may be purchased at any hardware store or outlet
>for a few dollars if you do not know how to check this with a volt
>meter, and are good for a life time.
>
>> >hmm, interesting. The 2 tubes I have put in to
>> >test the unit did flicker on startup and then were steady - less
>> >than 1 minute to get there.
>
>I have noticed that the BL tubes don't start well when they are
>cold, such as might be expected in an unheated room in the winter
>time, which is where I my exposure unit is located. This can be over
>come by allowing the tubes to heat up for 5 or 10 minutes prior to
>your printing session. When they are cold they are also less likely
>to come on instantly.
>
>Hope this helps,
>
>Don Bryant

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