Can UV LEDs erase EPROMs?

K

Kryten

Guest
I thought a UV LED EPROM eraser would be a compact gadget,
and wondered why I had not seen them already
(apart from EPROMs becoming obsolete).

Do they have the right wavelength or intensity for the job?

K.
 
This is slightly off-topic, but I bought a bunch of uv Leds, hoping that I
could use them to sterilise toothbrushes. I was informed by someone on the
newsgroup that they were far too underpowered, and not the correct
wavelength to do the job.
The UV bulbs in your average eraser are VERY VERY bright, and the leds that
I bought (supposedly the brightest that are available at this time) are not
anywhere near as bright.
As far as the wavelength, that I don't know.
Oh well.
Kim
"Kryten" <kryten_droid_obfusticator@ntlworld.com> wrote in message
news:iN8qd.3085$FT3.664@newsfe2-gui.ntli.net...
I thought a UV LED EPROM eraser would be a compact gadget,
and wondered why I had not seen them already
(apart from EPROMs becoming obsolete).

Do they have the right wavelength or intensity for the job?

K.
Click to expand...
 
Don Klipstein wrote:

I have heard of sunlight erasing EPROMS over several days
or a couple weeks in Arizona,
Click to expand...
I tried it. I made am EPROM filled with checkerboard pattern and ran
a continuos "test the EPROM" loop running from another, shielded
EPROM. Took 4 days before the test failed. After a week it still
didn't test on my burner as being fully erased.
 
"Guy Macon" <http://www.guymacon.com> wrote in message
news:10qjl047nrjp807@corp.supernews.com...
Don Klipstein wrote:

I have heard of sunlight erasing EPROMS over several days
or a couple weeks in Arizona,

I tried it. I made am EPROM filled with checkerboard pattern and ran
a continuos "test the EPROM" loop running from another, shielded
EPROM. Took 4 days before the test failed. After a week it still
didn't test on my burner as being fully erased.
That is a pretty good correlation to 'several days or a couple of weeks'.
Click to expand...
In terms of useability, the first failure was what mattered. In the UK (a
lot less Sun...), I have known a couple of test chips fail after about six
months, in equipment with no attempt to block light. Even when erasing the
EEPROM, in a proper eraser, it is very noticeable that some cells, seem to
take vastly longer than others. Unless the unit was 'tracking' the Sun,
presumably some cells were getting a lot more exposure than others near
the shaded edge, and these would take a long time to clear.
I doubt if a UV LED, could erase an EPROM in any reasonable time. The
light from these LED's, generally has more in common wth the longer
wavelengths given by UV flouresescent tubes, than the lamps used in
erasers.

Best Wishes
 
On Sun, 28 Nov 2004 13:34:43 +0000, Guy Macon
<http://www.guymacon.com> wrote:

Don Klipstein wrote:

I have heard of sunlight erasing EPROMS over several days
or a couple weeks in Arizona,

I tried it. I made am EPROM filled with checkerboard pattern and ran
a continuos "test the EPROM" loop running from another, shielded
EPROM. Took 4 days before the test failed. After a week it still
didn't test on my burner as being fully erased.
Click to expand...
An old Intel appnote suggested that the UV dose required for reliable
erasure is five times the dose required to erase all the bits.

John
 
Hmm, I guess the answer is no then.

There seems to be long UV for apps like making shirts glow in discos,
counterfeit note spotting, reading UV pens etc, and short UV for apps like
sterilizing stuff or wiping EPROMs.

I notice Maplin in the UK sell some UV LEDs for about Ł3 (N74AJ, 410nm peak,
500 mcd) and others (N75AJ)for Ł15.

I assume the fivefold difference is due to power output.

Strangely, the product images show them glowing violet.
Surely they should be invisible?
 
On Sun, 28 Nov 2004 18:54:08 GMT, "Kryten"
<kryten_droid_obfusticator@ntlworld.com> wrote:

Hmm, I guess the answer is no then.

There seems to be long UV for apps like making shirts glow in discos,
counterfeit note spotting, reading UV pens etc, and short UV for apps like
sterilizing stuff or wiping EPROMs.

I notice Maplin in the UK sell some UV LEDs for about Ł3 (N74AJ, 410nm peak,
500 mcd) and others (N75AJ)for Ł15.

I assume the fivefold difference is due to power output.

Strangely, the product images show them glowing violet.
Surely they should be invisible?
Click to expand...

410 is certainly not UV. I've never seen a "UV" led that's wasn't
brightly visible; these are actually violet LEDs. I think true
(invisible) UV LEDs are being produced now, but they're still very
expensive.


John
 
Nichia makes two incredible ultraviolet LED's, one is 365nm @ 100mw
and the other is 380nm @ 85mw. Yes thats right, 85 and 100 milliwatts
of OPTICAL output power! Both are single die (not arrays). You can
place an order and view datasheets at:

http://www.exoticelectron.com

Asa Cannell
 
On Sun, 28 Nov 2004 13:34:43 +0000, Guy Macon wrote:

Don Klipstein wrote:

I have heard of sunlight erasing EPROMS over several days
or a couple weeks in Arizona,

I tried it. I made am EPROM filled with checkerboard pattern and ran
a continuos "test the EPROM" loop running from another, shielded
EPROM. Took 4 days before the test failed. After a week it still
didn't test on my burner as being fully erased.
Click to expand...
Must be that pesky "ozone layer".

;^j
R.
 
The LEDs that I bought, that I mentioned in a earlier post, show very little
color at all, except for a VERY SLIGHT purple tinge. Strangely enough I took
a picture of one when it was on, and the picture showed a HUGE purple glow.
Kim
"Asa Cannell" <acannell@wwc.com> wrote in message
news:51ca721c.0411281516.2d1af2d3@posting.google.com...
Nichia makes two incredible ultraviolet LED's, one is 365nm @ 100mw
and the other is 380nm @ 85mw. Yes thats right, 85 and 100 milliwatts
of OPTICAL output power! Both are single die (not arrays). You can
place an order and view datasheets at:

http://www.exoticelectron.com

Asa Cannell
Click to expand...
 
On Mon, 29 Nov 2004 20:19:39 -0500, "Kim" <ksleep@sympatico.ca> wrote:

The LEDs that I bought, that I mentioned in a earlier post, show very little
color at all, except for a VERY SLIGHT purple tinge. Strangely enough I took
a picture of one when it was on, and the picture showed a HUGE purple glow.
Kim
Click to expand...
Cameras can see things people can't. A digital camera makes a great
near-IR viewer.

John
 
John Larkin wrote:

On Mon, 29 Nov 2004 20:19:39 -0500, "Kim" <ksleep@sympatico.ca> wrote:


The LEDs that I bought, that I mentioned in a earlier post, show very little
color at all, except for a VERY SLIGHT purple tinge. Strangely enough I took
a picture of one when it was on, and the picture showed a HUGE purple glow.
Kim


Cameras can see things people can't. A digital camera makes a great
near-IR viewer.

John
Click to expand...
Witness the embarrassing "I can see through your clothes" debacle
recently - I forget whose camera it was, one of the big Japanese firms,
but in IR mode it could see through clothes.

Cheers
Terry
 
Rich Grise wrote:

Is there some kind of article somewhere that tells more about this
"debacle?" This is the first I've ever heard such a thing, although I have
heard of using IR to see through clothes, anecdotally. (anecdotically?)
Click to expand...
I saw it on the news with pictures of the effect. I concluded that
it was a lot of imagination plus reporters looking for something
sensational - I just saw the clothes.
 
Kim wrote:

This is slightly off-topic, but I bought a bunch of uv Leds, hoping that I
could use them to sterilise toothbrushes.
Click to expand...
Don't tell me..You watched the mythbusters episode where they grow fecal
coliform on toothbrushes kept in the bathroom?
 
Kryten wrote:
Strangely, the product images show them glowing violet.
Surely they should be invisible?
Click to expand...
Well, the output may *peak* at 410nm, but It's a curve, with decreasing output
the further you go on either side of 410. So seeing some violet output is not
at all surprising. It's been a while, but I think violet is somewhere around
450, and blue is around 480 and onward.
 
In article <20041210023557.11425.00001872@mb-m29.aol.com>, K8JLF wrote:
Kryten wrote:

Strangely, the product images show them glowing violet.
Surely they should be invisible?

Well, the output may *peak* at 410nm, but It's a curve, with decreasing output
the further you go on either side of 410. So seeing some violet output is not
at all surprising. It's been a while, but I think violet is somewhere around
450, and blue is around 480 and onward.
Click to expand...
Depending on who you ask...

Violet stops and blue starts at 420-450, and blue ends and green starts
around 490-500...

And the band is not symmetric, falling off more sharply on the shortwave
side than on the longwave side. Blue and green LEDs also generally do
that.

Also, they called wavelengths 400 nm and longer (but shorter than blue),
and sometimes even as short as 380 nm, visible violet until these LEDs
came onto the market.

- Don Klipstein (don@misty.com)
 
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