Re: UV nail lamps for EPROM

On Fri, 18 May 2007 09:47:05 +1000, Bud Finley <budfinley@xxxxxxxxxxxx>
wrote:

Can anyone tell me if the 9W UV lamps sold as replacements for
cosmetic nail driers are suitable for EPROM erasing.

IOW are they genuine UV spectrum or some lesser version?

The price is certainly right.

Bud Finely

Mercury vapor UV lamps come in two varieties; long wave, 365 nm, and short
wave, 254 nm.

Low pressure mercury vapor tubes internally generate mainly short wave UV.
Tubes intended for producing visible light therefore have a phosphor which
glows in the visible when irradiated by short wave UV.

Tubes intended to produce long wave UV have a phosphor which glows in long
wave UV when irradiated by short wave UV.

The short wave UV doesn't penetrate glass, but long wave does (more or
less), so the "glass" of which the tube is made for visible and long wave
use is actual glass.

If the lamp must emit short wave UV, then the envelope is made of quartz,
or a high silica "glass", which does transmit short wave UV, and there is
no phosphor in this case. Such lamps are often designated "germicidal",
and when they're operating, you can usually smell some ozone near the lamp,
although there are so-called "ozone free" lamps.

Short wave UV will harm your eyes if you look at the operating lamp for
very long; a minute or two is enough to give you an object lesson. There
is no sensation of pain while you're looking, and you won't notice the
damage for hours. The short wave UV "sunburns" the conjunctiva and that
night while you're trying to sleep, it feels like your eyes are full of
sand. Every time you move them while they're closed, it hurts. Even
looking at a specular reflection of the lamp can burn your eyes.

Only short wave UV can erase EPROMS (that's why the transparent lid is made
of quartz), and if you look at these lamps:
http://cgi.ebay.com/9-watt-UV-nail-dryer-uv-LIGHT-BULBS-4-packcure-OPI_W0QQitemZ260118398132QQihZ016QQcategoryZ67653QQcmdZViewItem#ebayphotohosting
you will see that the tubes are white looking. That's because there is a
phosphor coating the inside of the tube. This means that this tube
produces long wave UV, which is what the nail dryers use.

On the other hand, these lamps:
http://cgi.ebay.com/9-watt-TUV-UV-light-bulbs-for-tetra-pond-filter_W0QQitemZ260119165752QQihZ016QQcategoryZ67653QQrdZ1QQcmdZViewItem
are transparent. There's no internal phosphor coating. These are short
wave UV lamps. But the socketing looks the same as the long wave tubes,
and I'll bet you could put one of the short wave tubes in this nail dryer:
http://cgi.ebay.com/9-watt-GEL-UV-light-Euro-110-V-Nail-dryer-Cure_W0QQitemZ260117186404QQihZ016QQcategoryZ67653QQrdZ1QQcmdZViewItem
and have yourself a cheap EPROM eraser. Just rig a shield so you won't be
exposed to the UV while it's turned on.
.

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