UV will penetrate plain glass and clear plastics, if you want to prevent this then you can get small pieces of glass from welding companies these are used as filters in welding helmets. A good example of UV light penetrating glass is the sunburn you get on your arms when driving, the light will be part UV and part IR. yes the glass will filter a small amount but not enough to stop your EPROM's being erased. if you want to cover the UV lamps in your EPROM eraser then use thin 2mm to 3mm polycarbonate.. this is what I used, my eraser used a Philips UV tube, cant remember the model as it was so long ago Behind the tube I used tinfoil to reflect as much as the light as possible I also put a small CPU fan in the housing as I found there was a bit of heat buildup after long periods of operation. Here is an interesting fact, If your looking for a filter for your IR. project get an old exposed film and use the piece that is not developed on the end's, it works pretty well. -----Original Message----- From: Sean Breheny To: PICLIST@MITVMA.MIT.EDU Date: Saturday, January 29, 2000 2:38 PM Subject: Re: First PIC project... >Hi Tim, > >You are correct about glass ATTENUATING UV, but I don't think that a think >sheet of glass blocks it ENTIRELY. Also, I think the UV wavelength used for >PCB exposure is considerably longer than that used for EPROM erasure, so it >might go through glass better than the short wavelengh UV. > >It seems to me that what is probably happening is that the glass cuts the >power considerably, but since the other Tim :-) has a full 60 watts of >power (of which a considerable fraction is probably longwave UV, because we >are talking flourescent bulbs), enough gets through to expose the film. > >Just a guess... > >Sean > > >At 07:11 PM 1/28/00 EST, you wrote: >>Yes...glass DOES block UV. If it didn't, then EPROMs wouldn't require quartz >>glass. Unless of course, you've discovered a new way of defeating this? I >>could be wrong, but that's what we learned in physics. >> >>My 1.9 cents, >> >>Tim Hamel >> >>In a message dated 1/28/00 3:25:57 PM Pacific Standard Time, >>stm800@CITY-NET.COM writes: >> >>> no... my light exposure box consists of 4 - 15 watt tubes uv radiating >>> (got a bluish tint) 1-1/2 inch apart...approx 4 inches high over the >>> window plate glass. which under it i have the film which is dark so dark >>> one could view the eclispse with it and see nothing,,,i expose for >about 30 >>> seconds and it is done ..... >>> >> >| >| Sean Breheny >| Amateur Radio Callsign: KA3YXM >| Electrical Engineering Student >\--------------=---------------- >Save lives, please look at http://www.all.org >Personal page: http://www.people.cornell.edu/pages/shb7 >mailto:shb7@cornell.edu ICQ #: 3329174