EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: ali6x944 on August 04, 2016, 12:00:18 pm
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Hi everyone,
I was searching about a homebrew way to make uv light of enough concentration to erase a UV eprom and I found this:
https://youtu.be/Rq94tgZOEWw
Is this real uv light and if so could it erase the uv eprom?
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No, it's just filtering out the longer wavelengths, most of what comes out will be the blue LED wavelength
For EPROMs you need a specific wavelength of shortwave UV.
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For EPROM erasing you need UV-C (200-280nm). Typical LEDs are not able to generate UV-C, so no, it does not work for EPROM erasing.
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Not only NO, hell NO.
The cheapest way to do it is a 4W T5 germicidal UV-C tube in a 4W fluorescent torch in a light-tight box. UV-C light is an eye hazard so make sure you cant see the light or any reflections with the original torch tube in before fitting the UV tube. The EPROM windows should typically be between 1/2 and 1 diameter from the tube surface.
You might be able to home-brew something with a carbon arc driven from an arc welder, but you'd need a fused quartz window, possibly a dichroic reflector to separate the IR and have massive amounts of waste heat to dissipate and would need to actively cool the EPROM.
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Is it possible to erase uv eproms using concentrated sun light? Say with a magnifying glass?
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If you use a lens for focusing sunlight into an EPROM, you will probably burn the EPROM instead of erasing the data because of the heat.
Another problem is, UV-C gets blocked by normal glass, therefore you need quartz glass for the UV-C light and an IR blocking filter for reducing the heating.
I haven't tried it, but it should be possible to erase an EPROM if it is exposed to sunlight for several weeks without any filters.
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I have. If I recall correctly, not a single bit had been erased.
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I have also tried sunlight erasure of PROMS. These were first generation PROMS so they had large design margins on the the well size and it was in the LA basin during the some of the worst smog years so it may not reflect results with newer PROMs or in a clear high altitude area, but two months exposure resulted in no loss of data.
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In the old days, when EPROMs were used, I used an UV arc lamp, made for "medical" purpose. It needed quite some power, but was reasonable fast (e.g. less than 20 minutes).
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Not only NO, hell NO.
The cheapest way to do it is a 4W T5 germicidal UV-C tube in a 4W fluorescent torch in a light-tight box. UV-C light is an eye hazard so make sure you cant see the light or any reflections with the original torch tube in before fitting the UV tube. The EPROM windows should typically be between 1/2 and 1 diameter from the tube surface.
Definitely that. Works perfectly, or if you can locate one of the ancient 'health lamps' that had those tubes too
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Do Xeon flash light have a potential to erase the uv eproms?
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No. Xeon photographic and stroboscopic flash tubes generally have borosilicate glass envelopes which block UV-C and may even have extra near UV filtering to avoid confusing the camera's Lux sensor and strange colour casts on the film or image.
See http://www.hakuto.com.tw/tw/dowfile.php?p=46 (http://www.hakuto.com.tw/tw/dowfile.php?p=46)
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No. Xeon photographic and stroboscopic flash tubes generally have borosilicate glass envelopes which block UV-C and may even have extra near UV filtering to avoid confusing the camera's Lux sensor and strange colour casts on the film or image.
See http://www.hakuto.com.tw/tw/dowfile.php?p=46 (http://www.hakuto.com.tw/tw/dowfile.php?p=46)
There have been some commercial EPROM erasers that used Xenon tubes, see: http://www.grifo.com/PROG/uk_Eraser.htm (http://www.grifo.com/PROG/uk_Eraser.htm)
I guess they used special quartz tubes.
You can still buy replacements if you want to experiment: http://www.dataman.com/erasers/strobe-bulb.html (http://www.dataman.com/erasers/strobe-bulb.html)
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Do Xeon flash light have a potential to erase the uv eproms?
No, and it would require hundreds of flashes even if it did. EPROMs require minutes of UV to fully erase.
Just buy a cheap UV eraser from eBay. They're cheaply made and use an appliance timer, but they work and cost <$15!
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Hi,
Hi everyone,
I was searching about a homebrew way to make uv light of enough concentration to erase a UV eprom and I found this:
https://youtu.be/Rq94tgZOEWw (https://youtu.be/Rq94tgZOEWw)
Is this real uv light and if so could it erase the uv eprom?
No, this is rubbish.
Here you can find some UV LEDs with wavelengths of about 265nm and 280nm which should do the job. One LED should be sufficient.
But be careful, this kind of UV radiation is dangerous, so a proper shielding of the radiation is a must!
http://www.epigap-optronic.de/led.html (http://www.epigap-optronic.de/led.html) (sorry, website is in German but I think you'll get the idea. Or google translate ;) )
I do also recommend a constant current source for the LED to make sure, that it is working in it's specs.
These LEDs are not really cheap things, so 10 - 50 Dollars per piece (there are some which costs much more) is not uncommon.
Suggestion for a constant current source:
https://www.mikrocontroller.net/wikifiles/2/28/Ksq.png (https://www.mikrocontroller.net/wikifiles/2/28/Ksq.png)
HTH,
Andreas
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Do Xeon flash light have a potential to erase the uv eproms?
No, and it would require hundreds of flashes even if it did. EPROMs require minutes of UV to fully erase.
Just buy a cheap UV eraser from eBay. They're cheaply made and use an appliance timer, but they work and cost <$15!
I actually have done just this with a regular "strobe" xenon flash. It was the only thing I had at the time (and no money) so I built a little flasher for it. It worked just fine, but it took days depending on the particular EPROM.
Nowadays I'm up to my armpits in UV-C bulbs. They're used for water sterilization, air sterilization in building's ventilation and hospitals. If you know anyone in those areas see if they have some old bulbs for you: they're often replaced on a schedule.
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Is it possible to erase uv eproms using concentrated sun light? Say with a magnifying glass?
It is just a question of UV intensity and exposure time
Yes, according to ST M27256 datasheet, you can easure the eprom using sun light
http://www.futurlec.com/Memory/27256_Datasheet.shtml (http://www.futurlec.com/Memory/27256_Datasheet.shtml)
ERASURE OPERATION (applies to UV EPROM) The erasure characteristic of the M27256 is such
that erasure begins when the cells are exposed to light with wavelengths shorter than approximately
4000 Å. It should be noted that sunlight and some type of fluorescent lamps have wavelengths in the
3000-4000 Å range. Research shows that constant exposure to room level fluorescent lighting could
erase a typical M27256 in about 3 years, while it would take approximately 1 week to cause erasure
when exposed to direct sunlight. If the M27256 is to be exposed to these types of lighting conditions
for extended periods of time, it is suggested that opaque lables be put over the M27256 window to
prevent unintentional erasure. The recommended erasure procedure for the M27256 is exposure to
short wave ultraviolet light which has wavelength 2537 Å. The integrated dose (i.e. UV intensity x
exposure time) for erasure should be a minimum of 15 W-sec/cm2. The erasure time with this dosage
is approximately 15 to 20 minutes using an ultraviolet lamp with 12000 mW/cm2 power rating. The
M27256 should be placed within 2.5cm (1 inch) of the lamp tubes during the erasure. Some lamps
have a filter on their tubes which should be removed before erasure.
typical white LED spectrum
(https://upload.wikimedia.org/wikipedia/commons/4/48/White_LED.png)
https://en.wikipedia.org/wiki/Light-emitting_diode (https://en.wikipedia.org/wiki/Light-emitting_diode)
The white LED strongest peak is at about 465nm, the intensity below 400nm is quite weak
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typical white LED spectrum
(https://upload.wikimedia.org/wikipedia/commons/4/48/White_LED.png)
https://en.wikipedia.org/wiki/Light-emitting_diode (https://en.wikipedia.org/wiki/Light-emitting_diode)
The white LED strongest peak is at about 465nm, the intensity below 400nm is quite weak
Yes, most of the fluorescent effect was probably due to visible violet, rather than UV.
Another possibility is the LED used in the phone had a violet LED to excite the phosphor, rather than blue, as it gives a better white, and will give more UV, than a blue LED.
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Thanks for all the help and thanks for clearing this for me...
You are the best ! :)