Hi Robin,
Thanks for the comprehensive info.
Do you think a car quartz halogen headlamp would have sufficient UV output ?
I have a new 12V dual filament 50W + 65W which I could parallel to give 115W
Alternatively, I have a new 12W T5 circular (11cm 41/2") Fly Zapper tube.
My PC is only 8cm x 3cm.
The sensitised PCB needs energy around 360nm.
Thanks,
John
--- 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/
>