Robin,
Does your 500W halogen connect directly to the mains or does it need a ballast or current limiter?
Do you use a base (socket) how do you connect to the bulb?
Thanks,
John G3UGY
> --- In Homebrew_PCBs@yahoogroups.com, Robin Whittle <rw@> wrote:
> >
> > Hi John,
> >
> > Generally, gas discharge tubes cannot be operated in parallel. They
> > need a high voltage to start, but settle down to a low voltage ca. 90
> > volts (I guess) once they are conducting. With ordinary inductor
> > ballasts I have seen two 20W short tubes, each with their own starter,
> > wired in series with a 40W ballast. This is for 240V. Maybe that would
> > work with a high frequency electronic ballast.
> >
> > I chose to use a 500 watt floodlamp from the hardware store. The short
> > linear quartz halogen lamps give off a lot of near UV, which is what I
> > want for exposing Riston negative photoresist.
> >
> > At a distance of about 45cm I have exposure times of 2 to 3 minutes.
> >
> > This is a much narrower angle source of light than having a bunch of
> > fluorescent tubes only 10cm away, so for a given phototool and possible
> > distance from the phototool to the top and bottom of the Riston, I get a
> > much sharper image (shadow).
> >
> > The only potential concern I can think of is heating of the phototool,
> > PCB and whatever means is used to hold them together. I have a fan
> > blowing on them to keep them cool.
> >
> > There's no warm-up time for a QI light. Tubular fluorescent lamps are
> > likely to have some kind of warm-up time, making it difficult to predict
> > their light output unless they have just been running and are fully
> > warmed up. High pressure mercury vapor lamps have much longer warm-up
> > times, and so do the compact fluorescent lamps which are now widely
> > used. All these fluorescent lamps - tubular, 400W (or other wattage)
> > high pressure mercury vapor lamps, and compact fluorescent lamps - come
> > in "black light" versions which I think put out the ideal wavelength for
> > exposing Riston.
> >
> >
> > http://www2.dupont.com/Imaging_Materials/en_US/tech_info/datasheets/index.html
> >
> > I haven't looked at all the types, but the types I have looked at are
> > specified to respond best to 350 to 380nm light. This datasheet for a
> > 400W high pressure mercury vapour fluorescent H500-BL:
> >
> > http://www.eyelighting.com/tb/Mercury/MVR/EQS-N-52-78-69917.pdf
> >
> > shows most of the output at about 370nm.
> >
> > However, I think their warm-up times are a problem.
> >
> > QI lamps will vary their near UV output somewhat according to their
> > operating voltage, but unless the mains voltage varies widely, I would
> > be surprised if this variation was enough to cause trouble with Riston.
> >
> >
> > - Robin http://www.firstpr.com.au/pcb-diy/
> >
>