UV nail lamps for EPROM

Brand and type? I doubt most of the men on this newsgroup have even seen what you're talking about, unless it can be used to harden epoxy.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Snooort!

But we do use nail polish. For fixing enameled wire onto ferrites...

Anyhow, can't this be tried out? Like running it for x minutes, then checking whether it has erased and once finding the point where it did work multiply the time by a safety factor y?

--
Regards, Joerg

http://www.analogconsultants.com

--being goofy--- Glue some EPROM's on your nails and drive over to the local nail spa for a drying.. :) Bring a timer...and use one finger at a time.. D from BC

Could turn into a nice biz opportunity when some kids with colorful Mohawk haircuts and leather clothes walk in. "Hey, cool, I want those

27256-2 nails!"

--
Regards, Joerg

http://www.analogconsultants.com

No, not the 27256. Use the 1702 for the gold! the little idiots do love their bling. :(

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

It'll go with the resistor nipple piercings, power diode tongue piercings,10Mhz clock crystal necklaces and schematic symbol tattoos..

I'd get the hysteresis symbol tattoo...that one's cool..

D from BC

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:

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:

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: 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.

Yes - these are germicidal type lamps and will work. Beware of serious eye hazard.

[... very good info on UV]

Thanks for posting this information, Phantom.

I have a question. I notice that silver chloride turns black when exposed to the light from ordinary office flourescent lights.

This reaction occurs when a UV photon forces a chlorine ion to give up an electron, which then converts a silver ion to a metal atom. The metal absorbs visible light and appears black. The reaction is quite strong with only two overhead lights. Here is a description:

2AgCl + 2UV --> Ag(s) + Cl2(g)

The same reaction occurs outdoors in sunlight. Since the short wave UV cannot penetrate ordinary glass, I assume the UV in this reaction is long wave UV.

However, manufacturers of flourescent lights, such as GE, insist that no UV escapes from their product. But obviously a great deal does escape.

Do you have any idea how the UV gets through the phosphor coating?

Regards,

Mike Monett

GE, publish the spectrum of their lamps, and show a small peak at

404.656nm, and a second somewhat larger one at 435.833nm, together with a general very low level of radiation beyond this. The 'black light' type lamps, typically produce perhaps 10* the peak intensity of either of these lines, at the shorter wavelength of about 370nm. GE, say that their lights should be used with 'CovRguard' fittings, or with UV sleeves, to completely eliminate UV (I don't know who said the bulbs themselves produce 'no' UV, if you talk to their commercial division, and specify that there must be no radiation above 400nm, in the illuminated area, they specify sleeves to be used...). They say that the total UV (beyond 400nm), is around 1/500th the level from noonday Sun, but not that their is 'none'. You'd need to work out whether it might be the two visible lines at the top of the spectrum, that are producing the effect, or 'UV'. I'd suspect it might be the visible lines, rater than 'UV'.

Best Wishes

Hi Roger,

Thanks for your very interesting post. Can you give the url for the info on the GE spectrum?

Untill now, my sources for the reaction of light on silver chloride claimed that UV light was needed to knock an electron loose from the chlorine.

However, I just discovered the following entry that shows the reaction is stronger at UV, but it still occurs even with red light:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ After hearing about William Herschel's discovery of infrared light in 1800, Johann Ritter decided to see if he could detect light beyond the other end of the spectrum - past violet. In 1801, he was experimenting with silver chloride, which turned black when exposed to light. He had heard that blue light caused a greater reaction in silver chloride than red light did and decided to conduct an experiment to see if this was indeed true. Ritter directed sunlight through a glass prism to create a spectrum and then placed silver chloride in each color. He found that the silver chloride increasingly darkened from the red to the violet part of the spectrum as predicted. Ritter then decided to place silver chloride in the area just beyond the violet end of the spectrum in a region where no sunlight was visible, and was amazed to see an even more intense reaction there. This experiment showed for the first time that an invisible form of light existed beyond the violet end of the visible spectrum. This is now know as the ultraviolet part of the electromagnetic spectrum.

/ritter_example.html

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I am very pleased to find this out. I was about to invest some time on an instrumentation project that would have not worked the way I planned:)

Regards,

Mike Monett

I once made a tie-tac out of an 8751 chip.

Nobody noticed. )-;

Cheers! Rich

I'd like to make some earrings (or any other pierced area rings) from machine shop chips and sell them in Hollyweird or Laguna Beach or something. ;-)

Cheers! Rich

Paper version sent to me at work, when I raised this question with regards to a commercial application which would be affected by light in the very near UV. I'd think they would send another copy, or may have it somewhere on their website as well. Just looked. They have a much lower resolution copy, showing the same peaks, but so poorly resolved, that it is hard to tell the exact frequencies. The spectra are at:

The curve I had, was for the 'WWX' lamp, with the paper copy ending at

370nm, where some significant output is still shown. The computer version seems to lose the bottom percent or so.

So it is responding to the visible, but more strongly to UV. A photo-chemist would probably be able to tell you the minimum energy photon required to trigger it.

Best Wishes

The curve I had, was for the 'WWX' lamp, with the paper copy ending at 370nm, where some significant output is still shown. The computer version seems to lose the bottom percent or so.

Great - thanks. The graphs show very little output above 375nm, and the FAQ states:

"UV exposure from sitting indoors under fluorescent lights at typical office light levels for an eight hour workday is equivalent to just over a minute of exposure to the sun in Washington, D.C. on a clear day in July."

So the UV output is negligible for any practical applications.

[...]

Thanks for your help. I'll try infrared and see if that works.

Regards,

Mike Monett

That's because you live in the Silicon Valley ;-)

--
Regards, Joerg

http://www.analogconsultants.com

No, actually John L is closer to Silicon Valley than I am - at the time, I was living and working in Orange County, a little quasi-libertarian bastion between LA and San Clemente. ;-)

Cheers! Rich

They probably mean the main strong shortwave UV wavelengths of low pressure mercury vapor.

The 365-366 nm cluster of mercury spectral lines does go through most glass well, and is a weak but slightly significant spectral feature of fluorescent lamps. Exception: Triphosphor lamps (including most compact fluorescents) of color temperature rating 3500K or higher usually in my experience have a blue-emitting phosphor ingredient that utilizes that UV wavelength.

Maybe silver chloride responds to the 404.7 nm violet wavelength of mercury, or has slight response to the violet-blue 435.8 nm wavelength of mercury that is strongly present in the light from fluorescent lamps.

indicates silver chloride reacting to visible blue and violet light as well as to UV.

also indicates ability of blue and violet visible light as well as UV to cause silver chloride to do its photochemical reaction.

Both of these note Ritter discovering UV via its great ability to cause the photochemical reaction in silver chloride.

A lot of fluorescent lamps have phosphor coatings that do not absorb longwave UV.

- Don Klipstein ( snipped-for-privacy@misty.com)

Interesting. I posted a link earlier from the same url that stated pretty much the same thing - silver chloride is not very sensitive to red light but is increasing sensitive to shorter wavelengths:

/ritter_example.html

Another link that confirms this is by Saul Bolaos. He describes how to make a gelatin emulsion of silver chloride to print pictures on irregular curved shapes such as an egg. He states the silver chloride emulsion is insensitive to red light:

So a red led may have little effect on silver chloride.

That makes good sense. I notice the reaction is much stronger with fluorescent than with incandescent lamps. But that may depend on the manufacturer - Roger Hamlett posted information showing GE lamps have very little emission beyond 370nm:

Thanks for the good information, Don.

Regards,

Mike Monett