Don’t Put That EPROM In Your Mouth!

[Jeremy] had some chips on hand that included EPROM.  We’re not talking about EEPROM, we mean EPROM that need a UV light source to erase. Most people don’t want to drop a few hundred dollars on a dedicated EPROM eraser, there must be another way.

Boy, EPROM really suck. But so do pacifiers and he already had a solution for exposing those to UV. He pulled out his $30 UV pacifier cleaner and tossed the chip inside. Two times through the cleaning cycle and the data was gone. We’ve looked into using UV LEDs to do the job but some experimentation shows that it doesn’t work. These pacifier cleaners are cheap and easy to get a hold of. The real question is are you still using chips that require UV for erasing?

60 thoughts on “Don’t Put That EPROM In Your Mouth!

  1. “Boy, EPROM really suck. But so do pacifiers”

    Oh hackaday, you didnt.

    he says that it’s impractical using LED’s to do this ‘probably because of the wavelength’.

    Can’t you buy different standards like IR Leds.

    (850nm, 950nm etc)?

    1. You can’t get practical LEDs in the short wave UV at like 250nm, which is what you want. Good old low-pressure mercury germicidal fluorescent tubes do the job nicely.

    1. Typically a human child only uses a pacifier for the first year or two of life. I would assume his kid already has grown out of that and he isn’t using the thing for pacifiers anymore.

  2. I’ll second Mark Richards in saying that I’m sure hoping that he doesn’t plan to ever use this sanitizer for sanitizing pacifiers again. The lead exposure from chips usually isn’t too much to worry about, until you think about it being ingested, which is exactly the kind of exposure here. I’m probably too anal when it comes to my kids and electronic boards/chips, but I always make them wash their hands after touching them, just in case they end up getting any of the lead into their mouths.

  3. lead…uv… yammie…

    seriously, to bad this is now all considered so horribly dangerous… ok, you don’t have to drink water for years that comes trough a lead pipe or so, but the amount of lead that might “come off” of an EPROM chip? seriously? Are you worried about that?

  4. @polossatik

    I have no idea how much lead may or may not be on these chips as a result of manufacturing or reworking. That said- lead paint is bad for children- it’s even worse for babies. Getting lead on their pacifier and then putting that in their mouth? It’s a stupid, and more importantly, POINTLESS risk. Buy a UV eraser for a few dollars. Replace the power supply for the eraser he already has for a few dollars.

  5. I bought fluorescent tube (about 5″) and it fits perfectly in those cheap handheld flashlight (w/ tube and bulb). I leave them both in a metal pencil case and check on them 15 min later. Total cost is around $5. That was 20 years ago. But I have to admit, I hardly use it. Maybe 5-10 times. Its value is more about the fact that I managed to make it all by myself, pre-internet.

  6. Clever hack.

    FWIW, leaving them out in the sun generally won’t erase anything very quickly. Tried that with a batch of 2716’s long ago. Left them on the outside windowsill from May-August. Still good at the end of the summer.

    Time, however, will degrade EPROMS. I recently tried to read a batch of 1702’s that had VTL2 for my Altair 680 on them. Data is corrupt, no programmer for 1702’s anymore. Time to punch it into some flash and build a board.

    As to the lead arguments, it does require a fair dose of ingested lead to do damage. The historical problems come from kids eating paint chips. Due to the lead oxide the paint chips tasted sweet, hence kids would eat a lot of them.

  7. I used to erase EPROMs by sticking them on the south side of a telephone pole. As I recall (from the C=64 days), they were erased within a week. This is in Southern California, maybe in other places YMMV. And it may even work better now with less of that pesky ozone layer!

    As far as the lead exposure, that’s just ridiculous. It’s not like the thing emits Lead Rays of Death. A chip just sitting there for a few minutes probably doesn’t leave even a trace of lead.

  8. Did anyone ever stop to think that maybe his kid is now older and doesn’t use pacifiers anymore? Nothing more annoying than a bunch of random people trying to give someone they don’t know parenting advice.

  9. I personally haven’t used EPROMs, I’ve seen them, but the few applications that I use PICs, I haven’t needed an older chip.

    And seriously, that picture, the chip is leads up, meaning that unless you dipped that chip in lead dust, or stuck a pacifier in there *with* the chip, you’re not going to get any lead in there. The fumes from soldering with leaded solder are waaaaay more harmful for you, and even then, they won’t kill you.

    Hasn’t anyone else held solder in their mouth when they needed an extra hand? Or am I the only one with complete disregard for “allowable limits”?

    1. Yes, I “chewed” on lead-tin solder about one hour a day on average between my 6th and 12th or so. And look, I’m still not dead or taken into a mental institution. I think the ozone generated by that cleaner is WORSE than the single molecule of lead that falls off.

  10. – Hasn’t anyone else held solder in their mouth when they needed an extra hand? Or am I the only one with complete disregard for “allowable limits”?-

    @Cole: Yes. And many other ‘you shouldn’t do that’ type things like stripping wire with my teeth (I was young and stupid), testing a 9V with my tounge, spending countless hours working on projects in the basement of a 100+ year old house most likely FILLED with radon gas and asbestos on the pipes.

    I’m not dead yet. Helicopter parents is about the truth. How the hell are we supposed to learn anything if we’re deathly afraid to try it?

    Good post btw..

  11. I use eprom’s on a daily basis (27c256) for EFI tuning on turbo hondas. I use a 12″ UV bulb thats used in aquarium filters for sanitation and it works great; i can erase like 20 eproms at a time in about 10 minutes. I set the eproms so that the window is about 1/2″ from the actual bulb; set a timer for 10-15 minutes and check them all to see if they’re blank and they are. Cost me like $20 for the bulb and a 12″ florescent housing from wal-mart

  12. So wait – if an eeprom is frowned upon what’s the preferred device for storing small amounts of information on an embedded device that doesn’t need to be removed (i.e. when you wouldn’t use an SD card)?

  13. It’s off topic, but what the hell:

    If you have kids, it changes things. The significant time investment in them that they require changes your perspective quite a bit. Not to mention the love you have for them. You don’t need to be a helicopter parent to stop and say that something isn’t safe or smart. I agree again with Mr. Richards that it’s a POINTLESS exposure, one that can be controlled, so do it. Sure, it’s probably not that big of an exposure, but isn’t it still silly to cause ANY exposure?

    It’s like people commenting to me these days about the sillyness of carseats, being that “we used to ride around without them, and we lived”. Sure, we did, but scores of kids DIDN’T, which is why they’re a legal requirement now. You can go overboard, always a possibility, but for pete’s sake people, not everyone who’s concerned about a kid’s safety is a “helicopter parent”. It’s always a fine balance between being too risk averse, and letting your child learn, but letting them play with things that really can be a source of long term damage is something I think worth avoiding.

    Just my quarter byte’s worth. Flame away…

  14. What I always wanted was a second hand UV curing lamp from the dentists office but I imaging we are still talking hundreds of dollars. At any rate, the output tube is very close to the same size as the typical UV window and with such awesome wattage the typical 20 minutes might be over in 30 seconds? I don’t do them that much anymore so I don’t drool anymore for the dentist’s lamp.

    Namlak – those eproms on the telephone pole weren’t erased, the CIA was just replacing them to steal your code! It takes 6 months of sunlight to begin to make data unreliable or 10 years of typical office florescent lighting or 10 minutes in an EPROM eraser, and that from an Intel datasheet from the mid 80’s. Make it 20 minutes to ensure that the device is completely erased. I imagine that’s about the same time frame that the pacifier sanitizer is using too. About the same price range. Hundreds of dollars for a real EPROM eraser? I don’t think so, I sure won’t pay that for one.

    Lead risk issue is pointless AND undetectable, do what you want to here, go all anal on somebody else though.

  15. Brett,

    You’re referring to another technology, EEPROM is not the same as EPROM. They’re both eraseable, but eeprom doesn’t require the UV eraser, thus the extra “E” meaning “electrically erasable read only memory”. So using EEPROM is fine for what you describe. The topic here is that EPROMs and Microcontrollers that are built using that as their code storage are a pain in the ass to erase because they require UV to set them back to their blank state.

  16. The problem is that lead in lead solder is relatively inert. It takes a bit of effort to remove it from the alloy. Unless the solder itself is coming off the legs of the chip, it’s not going to leave lead inside the UV cleaner.

    Moreover – if one is using SOCKETED EPROMS – there shouldn’t be any solder on the legs of the chip to start with.

    The casing of the chip itself is likely plastic or ceramic. No worries there either.

    In any case, one can CLEAN surfaces. Even if he needs to worry about contaminating his cleaner, a wipe down with a damp wash cloth should solve that problem.

    Yes, limiting needless exposure to toxins is a good thing. But crying OMG WTF THINK OF THE CHILDRENS is just insane.

  17. That’s a tiny eprom; I remember using ones that you couldn’t even fit in your mouth (well.. without getting cut up at least).

    Also, we erased eproms with one of those uvlight sticks you can get for nothing glued inside of a little box… worked fine if you waited long enough.

  18. Lead is fine. Chill out.

    Metallic lead really isn’t all that bad, smilr is right. Lead that’s gone into solution isn’t good, but metallic lead is okay. Solid lead pipes were used for hundreds and hundreds of years. More recently (last hundred years or so) lead solder has been used to join pipes. A great number of buildings still have great deal of lead in the drinking supply. It’s only very recently that metallic lead has been removed from everyday life.

    Think about it. Ever hear of somebody who’s been shot but they can’t get the bullet out? People live out their lives with metallic lead inside their bodies. It’s no big deal.

  19. Working with EPROM is something I don’t really miss. I always tought it was a waste of time, waiting for them to erase and program.

    Back in the days, I always did my development on EEPROM with similar pin-outs, like using a 28C256 instead of a 27C256. These EEPROMs required no erase cycles, and programmed much faster than EPROMs.

    I even had a chip, a Dallas DS1225Y, which is a combination 8Kx8 SRAM with an integrated lithium battery for data retention, with a pinout compatible with 27C256s. This made programming blazingly fast and no erase cycles! The battery was rated for 10 years. I have one from 1993 and its data is still intact as of today.

    I substituted the EEPROM/NVRAM with an EPROM only when the firmware development was completed.

  20. you can get toothbrush uv cleaners that are very similar to the pacifier, haven’t tried it yet but it should work.

    plus it has a neat little 5 minute push button timer to boot.

    fwiw, i tried using uv leds and no go. you might erase a few cells with a week’s exposure but its cheaper and simpler to use the correct tool. However these chips *are* sensitive to ambient light, will affect 12C508JWs and others.

    one thing i meant to try is grounding all the pins and putting a sanded down otp pic on a corona generator panel (OAUGDP) to see what happened.

  21. @Cole
    You’re right, solder fumes are way more dangerous in terms of health problems. The flux is an irritant and can induce asthma and dermatitis.

    Lead vaporizes at 1749C/3180F, and it’s safe to assume that no consumer soldering iron will reach that temperature.

  22. >Most people don’t want to drop a few
    >hundred dollars on a dedicated EPROM eraser,
    >there must be another way.

    So they go on ebay and buy an eraser for around $30.. you even get a timer! Is there any reason to falsely inflate the price of a dedicated eraser other than to make the “hack” seem better than it actually is?

    Also.. why are EPROMs bad? There’s plenty of places you might want to use them. EEPROMs aren’t that big and FlashROM has it’s own set of issues.. Someone mentioned NVRAM; High capacity NVRAMs will set you back more that the eraser and a pile of equivalent chips. Also true of FRAM.

    If you’re “hacking” any cartridge based console a cheap burner and eraser are very handy.

  23. OK so here’s the deal: EPROMS store information as electrical charge in the buried gate of a MOSFET. It’s a capacitor. So, to erase an EPROM you have to discharge that capacitor. How do you do that? Ionizing radiation. The photon energy of hard UV (aka UV-C) @ 254nm is high enough to ionize atoms and smash molecules. That’s where the ozone smell comes from when you run a UV-C lamp. The O2 molecules get smashed into Os … that’s also why UV-C is germicidal: it smashes holes into the DNA of those little critters. Which means it’s not too healthy for humans either.

    Now, there’s really no need to use clumsy old EPROMs. There are flash ROMs that are pin compatible with most EPROMS (29C256 is a good part). For other flash chips you can easily wire up an adapter board.

  24. To follow up what @glangar said: It won’t work with UV LEDs since (last I checked) they haven’t managed to create a junction that emits at the UV-C band (~254 nm).

    I wonder how fast you could erase one with a few mJ of KrF Excimer laser radiation (around 248 nm @ 20 Hz).

  25. Yes, some of us still use EPROMs, the erasing and programming aren’t a problem (I have access to an eraser) but the bit level programming tends to drive me nuts….get everthing right, and as Professor Frink says “Oh dear, forgot to carry the one”

  26. um cigar box + small light fixture and germicidal uv bulb, the whole setup would cost about 10 bucks and you would not have a billion people worried about a stray atom of lead near a child

  27. To be honest, some of the whining about this hack really surprises me. In my mind, hacking is ultimately a matter of thinking outside of the box. Using a pacifier sterilizer to erase an eprom is precisely that.

    Now, assuming I had a baby, a sterilizer, and a chip that needed erasing, would I borrow junior’s gizmo to blank my chip? Probably not.

    There is no intrinsic danger in transporting gasoline in a properly-marked metal canteen, for example, but it’s not a good idea. Some things are best kept separate, simply as a matter of organization and good practice.

    Likewise, an atom or two of lead will not hurt anyone, but toxic metals and tiny, ingestible parts with sharp pins are inherently infant-un-friendly materials. As a matter of good practice, you keep babies and these materials apart.

    That said, no self-respecting Macguyver fails to stop at every garage sale and thrift shop in search of cool, cheap things to take apart/modify, and these are precisely the kinds of places you might find a used pacifier sterilizer for a buck or two. This is the one you can buy and keep in the workshop, “just in case.”

    I applaud the author’s ingenuity, and I will add this piece of hack trivia to my mental database. One never knows when a trick like this may come in handy.

  28. check back next month everyone for my new device
    it takes used car batteries and melts down the plates with a little rubber and it molds it into pacifiers(yay spongey lead/rubber hybrid!)
    hm, if i leave the acid in will they be self galvanising?

    $7 13 watt black light CFLs would do a decent job of erasing eprom though no?

    maybe 15 min exposure?

  29. @Frogz:

    … More like weeks or months of exposure.

    What most people don’t realize is that the ultraviolet UVC light needed to erase EPROMs is absorbed by normal glass. Only transparent quartz let it through. That’s why the erasure window on top of an EPROM is made of quartz, not glass. Also, germicidal UVC fluorescents are made of quartz, not glass.

    Also, very important to anybody who wants to build his own eprom UV eraser:

    UVC germicidal lamps are extremely hazardous to the eyes. Just a few seconds of exposure to its “invisible” light can render you COMPLETELY BLIND! It should only be powered on when fully enclosed and no light can escape the enclosure.

    These lamps can do much more damage than the few atoms of lead on a pacifier!

  30. Guys I used to eat spagetti or baked beans every morning while while surfing, cooked on a fire in the can. I’ve probably got more lead inside me than a car battery :p and I’m still alive, don’t know how but I am

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