Is this real UV? - Page 1
Forum section: electronics / beginners

author: ali6x944
author_rank: Frequent Contributor
timestamp: August 04, 2016, 12:00:18 pm
content: 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/Rq94tgZOEWwIs this real uv light and if so could it erase the uv eprom?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 04, 2016, 12:12:27 pm
content: No, it's just filtering out the longer wavelengths, most of what comes out will be the blue LED wavelengthFor EPROMs you need a specific wavelength of shortwave UV.

author: bktemp
author_rank: Super Contributor
timestamp: August 04, 2016, 12:15:14 pm
content: 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.

author: Ian.M
author_rank: Super Contributor
timestamp: August 04, 2016, 12:16:45 pm
content: 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.

author: ali6x944
author_rank: Frequent Contributor
timestamp: August 04, 2016, 02:52:05 pm
content: Is it possible to erase uv eproms using concentrated sun light? Say with a magnifying glass?

author: bktemp
author_rank: Super Contributor
timestamp: August 04, 2016, 03:05:18 pm
content: 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.

author: AndyC_772
author_rank: Super Contributor
timestamp: August 04, 2016, 03:58:47 pm
content: I have. If I recall correctly, not a single bit had been erased.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: August 04, 2016, 04:42:46 pm
content: 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.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 04, 2016, 04:53:50 pm
content: 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).

author: CJay
author_rank: Super Contributor
timestamp: August 04, 2016, 04:54:46 pm
content: Quote from: Ian.M on August 04, 2016, 12:16:45 pmDefinitely that. Works perfectly, or if you can locate one of the ancient 'health lamps' that had those tubes too

author: ali6x944
author_rank: Frequent Contributor
timestamp: August 05, 2016, 03:54:58 pm
content: Do Xeon flash light have a potential to erase the uv eproms?

author: Ian.M
author_rank: Super Contributor
timestamp: August 05, 2016, 04:14:43 pm
content: 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.Seehttp://www.hakuto.com.tw/tw/dowfile.php?p=46

author: edavid
author_rank: Super Contributor
timestamp: August 05, 2016, 04:24:36 pm
content: Quote from: Ian.M on August 05, 2016, 04:14:43 pmThere have been some commercial EPROM erasers that used Xenon tubes, see:http://www.grifo.com/PROG/uk_Eraser.htmI guess they used special quartz tubes.You can still buy replacements if you want to experiment:http://www.dataman.com/erasers/strobe-bulb.html

author: timb
author_rank: Super Contributor
timestamp: August 05, 2016, 08:19:25 pm
content: Quote from: ali6x944 on August 05, 2016, 03:54:58 pmNo, 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!

author: BU508A
author_rank: Super Contributor
timestamp: August 05, 2016, 09:00:23 pm
content: Hi,Quote from: ali6x944 on August 04, 2016, 12:00:18 pmNo, 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(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.pngHTH,Andreas

author: Paul Moir
author_rank: Frequent Contributor
timestamp: August 05, 2016, 10:56:02 pm
content: Quote from: timb on August 05, 2016, 08:19:25 pmI 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.

author: crazyguy
author_rank: Regular Contributor
timestamp: August 06, 2016, 08:32:45 am
content: Quote from: ali6x944 on August 04, 2016, 02:52:05 pmIt is just a question of UV intensity and exposure timeYes, according to ST M27256 datasheet, you can easure the eprom using sun lighthttp://www.futurlec.com/Memory/27256_Datasheet.shtmlERASURE OPERATION (applies to UV EPROM) The erasure characteristic of the M27256 is suchthat erasure begins when the cells are exposed to light withwavelengths shorter than approximately4000 Å.It should be noted that sunlight and some type of fluorescent lamps have wavelengths in the3000-4000 Å range. Research shows that constant exposure to room level fluorescent lighting coulderase a typical M27256 in about 3 years, while it would take approximately 1 week to cause erasurewhen exposed to direct sunlight. If the M27256 is to be exposed to these types of lighting conditionsfor extended periods of time, it is suggested that opaque lables be put over the M27256 window toprevent unintentional erasure. The recommended erasure procedure for the M27256 is exposure toshort wave ultraviolet light which has wavelength 2537 Å.The integrated dose (i.e. UV intensity xexposure time) for erasure should be a minimum of 15 W-sec/cm2.The erasure time with this dosageis approximately 15 to 20 minutes using an ultraviolet lamp with 12000 mW/cm2 power rating.TheM27256 should be placed within 2.5cm (1 inch) of the lamp tubes during the erasure. Some lampshave a filter on their tubes which should be removed before erasure.typical white LED spectrumhttps://en.wikipedia.org/wiki/Light-emitting_diodeThe white LED strongest peak is at about 465nm, the intensity below 400nm is quite weak

author: Zero999
author_rank: Super Contributor
timestamp: August 06, 2016, 12:12:25 pm
content: Quote from: crazyguy on August 06, 2016, 08:32:45 amYes, 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.

author: ali6x944
author_rank: Frequent Contributor
timestamp: August 12, 2016, 09:50:14 pm
content: Thanks for all the help and thanks for clearing this for me...You are the best !