UV LED to erase EPROMs, need update

Discussion in 'Embedded Systems and Microcontrollers' started by hp1729, Jul 15, 2016.

  1. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
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    Last time I looked into erasing an EPROM with an LED the only ones available were 400 nm. Can I get a confirmation from somebody that I need 250 nm? How bright? I can find a few but at a $150 price range. Does anybody have newer information? Digikey has 280 nm.Is that close enough?
    Example attached. MTE280. output power only 1.5 mW at 20 mA, about 7 V. TO-39 case. About $150.00.
    280 nm. Very narrow spectrum (like 10 nm). But would 280 nm erase an EPROM? Does anybody have some experience with this?
     
    Last edited: Jul 15, 2016
  2. DickCappels

    Moderator

    Aug 21, 2008
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    What is the part number of the device you want to erase? The wavelength should be mentioned in the datasheet.
     
  3. Tonyr1084

    Active Member

    Sep 24, 2015
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    I've heard - keep in mind I said "I HEARD" - doesn't mean "I know", but I heard that if you leave them in the sun they will be erased. Has some believable components to it and if I ever had to erase an EPROM, rather than drop that much money on an eraser I think I'd try it. If it fails - I'm out exactly $0.00 and maybe a day or two.
     
  4. Robin Mitchell

    Well-Known Member

    Oct 25, 2009
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    I can confirm that a few days in the sun (bright days) will erase an EPROM :)
     
  5. benta

    Member

    Dec 7, 2015
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    I highly doubt if you can erase an EPROM in reasonable time with a UV-LED with only 1.5 mW power.

    The normal small erasers use a 4 W UV tube at 250 nm.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    UV erasers are~$10.00 on Ebay.
    Max.
     
  7. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
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    I didn't think of that. It was too obvious. Yep 250 nm (2500 Ang), 12 mW/cm2 for 15 minutes. So I would need ten $150 chips or wait ten times longer (if that worked at all)..
    I guess we won't do that this year.
     
    Last edited: Jul 15, 2016
  8. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
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    Las Vegas here. Yep lots of free sun. I just didn't want to wait all day. But, it does work. The data sheet is very specific about 2537 Angstrom wavelength. It doesn't say how far from that it can work. I don't know if 280 nm would just take a little longer. I know 400 nm doesn't do anything quick.
     
    Last edited: Jul 15, 2016
  9. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
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    Thanks. I was just hoping somebody knew of a cheap LED solution. Not this year.
     
  10. Spaff ffapS

    New Member

    Jun 6, 2016
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    I do have experience erasing EPROM with Mercury UV lamps, 15 minutes. They were about the diameter of a pingpong ball with candelabra screw base, and need a small ballast coil. They were sold a zillion years ago as "odor lamps" because they make ozone, and were commonly used in clothes dryers. An old appliance junk yard might have them for nearly free or see if findable on Ebay.
     
  11. benta

    Member

    Dec 7, 2015
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    Why on earth don't you just buy the 10...15$ eraser that Max mentioned?
    They usually take 4...6 EPROMs at once, if needed.
    Yes, they don't have a sexy UV-LED, but they work. And 253.7 nm works for all EPROMs.

    Benta.
     
  12. hp1729

    Thread Starter Well-Known Member

    Nov 23, 2015
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    That is about what I have now. Just keeping up on the state of things. what I can't find is "250 nm + or - how much"?
     
    Last edited: Jul 15, 2016
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Sounds like the motto we have around here, 'If it works, we can always change it';)
    Max.
     
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  14. ian field

    Distinguished Member

    Oct 27, 2012
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    If you don't put stickers over EPROMs, they'll erase under room lighting - eventually.

    Probably quicker under fluorescent.
     
  15. MaxHeadRoom

    Expert

    Jul 18, 2013
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    This has happened on more than one occasion where machinery cabinet doors have been left open during hot summer days and if the sticker has come off or never been on the eeproms and the cabinet happens to face an open window, all of a sudden the machine loses its memory!:eek:
    Max.
     
  16. RichardO

    Well-Known Member

    May 4, 2013
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    I don't think the exact wavelength is required. My understanding is that the wavelength specified in the data sheets was chosen because mercury lamps are easy to get. It would be interesting to know what range of "colors" actually work and how well.
     
  17. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Wikipedia has an unreferenced claim about time vs. wavelength under EPROM...

    Erasure of the EPROM begins to occur with wavelengths shorter than 400 nm. Exposure time for sunlight of one week or three years for room fluorescent lighting may cause erasure. The recommended erasure procedure is exposure to UV light at 253.7 nm of at least 15 W-sec/cm² for 20 to 30 minutes, with the lamp at a distance of about 2.5 cm.
     
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  18. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    253.7 nm happens to be a very intense band in mercury lamps. It may be quenched in high pressure lamps, but in low-pressure lamps (often called germicidal lamps) it is 90% or more of the emitted light energy. There is nothing mystical about that wavelength for erasing EPROM's. It was simply available in high intensity, relative spectral purity, and cheap.

    Of course, it is UVC and a user needs to take appropriate precautions.

    John
     
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