Re: Eprom Eraser, how to build

Asimov wrote:

> "Mark Zenier" bravely wrote to "All" (11 Nov 05 03:41:15)
> --- on the heady topic of "Re: Eprom Eraser, how to build"
>
> MZ> From: mzenier@xxxxxxxxxx (Mark Zenier)
> MZ> Xref: core-easynews sci.electronics.repair:348213
>
> MZ> In article <1131574148.397613.278000@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
> MZ> Andy <andysharpe@xxxxxxxx> wrote:
> > Is it possible to build an inexpensive UV EPROM ERASER out of those
> >innexpensive UV LED Flashlights or the bulb from a bug zapper such as
> >this one:
> >
> >Andy writes:
> >
> > No. The frequency of the emission of a UV LED is far removed from
> >the
> >particular NARROW band of UV frequencies that can erase an EPROM...
> >
> >I forget the actual center frequency needed for EPROM erasure, but if
> >the
> >spectral frequency is not very very close to it, the EPROM won't erase.
> >If you research it on the internet, you will learn a great deal...
>
> MZ> And a lot of what you learn will be WRONG.
>
> MZ> An EPROM cell will get erased by any electromagnetic radiation
> shorter
> MZ> in wavelength than some limit determined by the device physics. (You
> MZ> can even use X-Rays is you can find a source powerful enough).
>
> MZ> But that wavelength is shorter than the 350 nanometer output of a lot
> MZ> of UV lamps. Ie. the /BL or /BLB "poster lights" that are relatively
> MZ> safe. These can light up the phosphorescent ink on posters, cure glue
> MZ> or printed circuit etch resist, but not erase EPROMs. (Or at least
> not
> MZ> in any reasonable length of time. Back in my starving student days I
> MZ> did it with a poster lamp, but not many people want to wait for 3 1/2
> MZ> days).
> MZ> A 300 nanometer tanning bed lamp will do it in about an hour, a 258
> MZ> (?) nanometer germicidal lamp in just a few minutes. In other
> words, MZ> if you can't get a sunburn or worse, it won't erase an EPROM.
>
>
> An alternative is the warm midday sun in the summer. Someone tried to
> convince me I could leave an eprom out on the beach for years and it
> wouldn't erase but that was bs as anyone who gets a sunburn can attest.
> I exposed pcb's outdoors in my early experiments. It took about 12
> minutes under the Sun compared to about 2 minutes with a proper lamp.
>
> A*s*i*m*o*v
>
> ... Puddy-tat's not so bwave in Gwanny's microwave!

I tried eresing EPROMs in the sun, in Australia (i.e. proper sunlight).
>From what I can remember, it took more than a week. That makes me very
scared of looking into one of those eraser tubes which can do it in
minutes. PCB resist uses longer, less dangerous wavelengths.
Chris

.

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