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UnderColor, Volume 1, Number 2, December 25, 1984
- Title: EPROM Erasers
- Author: Martin Goodman, M.D.
- Synopsis: Things you should know first.
- Page Scans: Link
For other than industrial use, probably the best bet in UV erasers is to buy a bottom of the line commercial EPROM eraser. Such items, which can erase one to three EPROMs in 10 to 20 minutes, are available from a number of suppliers for about $40. If you are a do-it-yourselfer, you can make your own out of a light·tight box (l used a cheap tool box) and a short-wave UV (germicidal) light bulb. I used a GE G15T8 bulb (18 inches long). Whatever bulb you use, it must have a rated max output wavelength around 2537 Angstrom units. Long-wave UV bulbs (the kind used for sun-tanning systems) will not work well at all. Do not use suntan UV bulbs to try to erase EPROMs! They will erase the EPROM eventually, but will take hours. The box I made ended up costing me about $80 total in parts (including an auto·resetting timer l got for it), and is a bit bulky. On the other hand, it is capable of erasing over 60 EPROMs at once.
Once you have an EPROM eraser, it is essential that you calibrate it for the particular EPROM type(s) you are going to erase. After extensively reviewing the literature on this subject, here is my advice: Take an EPROM and program it. Then put it in your eraser and expose it for 30 second intervals. After each exposure, check to see if it’s fully erased.
When you have determined the minimal exposure time needed to erase the EPROM, multiply that time by five. That is the amount of time needed to reliably and properly erase that brand of EPROM. Different EPROM types and different brands will have different erasure times, varying by up to a factor of four. Using this guideline you can be assured of complete and proper erasure. And you never have to worry about complicated equations involving "nominal erasing energy" in watt sec/cm squared!
Why a light-tight box? UV radiation is extremely damaging to the retina. Even the weaker tanning UV lights can, with long exposure, blind an unwary sun worshiper. The short-wave UV used for EPROM erasing is much more dangerous than tanning UV light. If you wear glass spectacles, your eyes are fully protected, as glass is opaque to short-wave UV. Plastic and quartz can’t block short-wave UV. Even if you do wear glass lenses, you must make your EPROM eraser light-tight to protect others who may wander near it.
A brief note on tanning: I, like you, burn rather than tan. Actually, that is a blessing, as current medical knowledge strongly indicates that sun bathing and tanning is quite unhealthy. UV exposure of skin predisposes it to several forms of skin cancer and always results in skin aging much more rapidly.
Added Note: If the time to apparent erasure is less than one minute, it means your EPROM is too close the UV bulb and is getting too intense UV. Just arrange your eraser so the EPROM is further away from the bulb, and try again.
Editor’s Note: CompuServe users will recognize this article from The Color Sig. Our thanks to Marty for letting us print it! (end)
[Reviewer's Note: Contrary to the statement above glasses with glass lenses will not protect you from your UV lamp. Not all glass will block UV radiation. Thickness and chemical composition will determine the degree of UV blocking. Further, light can enter your peripheral vision around the edges of your frame. Do not look at the UV lamp regardless of what you are wearing! RG]