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PICList Thread
'Build Your Own UV Eraser'
1998\10\14@144127 by Thomas McGahee

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For those who wish to build their own UV eraser I offer the
following details regarding a UV eraser that I built and have
used successfully for several years to erase PICs and EPROMS.

LAMP:
Westinghouse G8T5 Ultraviolet lamp
(Sold as a germicidal lamp)

LAMP SOCKETS (2):
Standard miniature two pin fluorescent lamp socket

BALLAST:
Universal MFG Corp Paterson, NJ
6-8 watt Ballast
118V 60Hz .158A
Catalog # 549

START SWITCH:
Standard F.L.S. (Fluorescent Lamp Switch) rated at 40 watts.
This eliminates the need for a starter.
You push it for a few seconds to bring the filaments up
and then release to run. If desired, you can instead
use a lamp starter module rated from 10-20 watts and a
regular on/off switch.

CASE:
12.25" x 4" x 4" (internal dimensions)
Plastic cassette tape storage box with plastic cover.

The Ballast mounts on the inside bottom of the case,
and the lamp sockets mount about an inch below the
top edge of the case, so that the UV lamp will be
positioned right down the middle of the case.

The 12" length of the UV tube allows me to erase several
PICs or EPROMS at the same time. As with all UV lamps,
avoid looking at the lamp while it is operating.

My particular
unit is built with all the parts mounted inside the box. The
box is turned upside-down and placed on top of what would
usually be the cover. The PICs or EPROMS are lined up
down the middle of the cover, the box is placed into the
cover (which is also upside down), and then the unit is
turned on. Erasure takes only a couple of minutes. You can
speed up erasure time by placing the chip erasure window
even closer to the UV lamp. I usually use pieces of that
black or pink anti-static carrier foam to hold the chips
where I want them to be.

Chips to be erased should not
be too near the ends of the lamp, as UV output there is
slightly less than that found along the rest of the lamp.

Hope this helps.
Fr. Tom McGahee

1998\10\14@151452 by Richard A. Smith

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On Wed, 14 Oct 1998 12:49:05 -0400, Thomas McGahee wrote:

>The 12" length of the UV tube allows me to erase several
>PICs or EPROMS at the same time. As with all UV lamps,
>avoid looking at the lamp while it is operating.

My sister owns a Tanning Salon and I have been to several tech training session
on UV lamps.  I think saying avoid looking at
the lamp while operating is a little weak.  Perhaps the whole tanning industry i
s paranoid, but considering the ammount
warnings I have seen given for tanning lamps that only emit UVA and UVB anything
that emits UVC should be treated with
much more respect.

I would say do every effort possible to make sure you don't view the lamp while
operating.  One or two quick exposures won't
hurt anything but repeated exposure over a year or so will do some serious damag
e to your retina. (or you fingers or what ever
else comes in contact with the UVC)

As for the eraser we use almost the exact same setup here and it works great.  I
can erase almost a whole rail of EPROMS in
about 10 minutes.



--
Richard A. Smith                         Bitworks, Inc.
spam_OUTrsmithTakeThisOuTspambitworks.com               501.521.3908
Sr. Design Engineer        http://www.bitworks.com

1998\10\28@210043 by John Payson

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| You can
| speed up erasure time by placing the chip erasure window
| even closer to the UV lamp. I usually use pieces of that
| black or pink anti-static carrier foam to hold the chips
| where I want them to be.

I would suggest the black material over the pink; the black
material is slightly conductive, ensuring that any static
charge on any part of its surface will slowly spread out over
the entire thing; thus it's impossible for one spot on the
foam to hold a charge relative to the rest of it.  The pink
stuff works by refusing to easily accept or give up electrons
on its surface (so it won't take a charge in the first place).
In many situations this is just as good, but strong UV can
cause ionisation (i.e. electrostatic buildup) in many materials
including those inside the PIC and it's probably a good idea to
give those ions a safe path lest they find an unsafe one (e.g.
by breaking down the PIC's dielectric).

1998\10\28@212947 by Mark Willis

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John Payson wrote:
>
> | You can
> | speed up erasure time by placing the chip erasure window
> | even closer to the UV lamp. I usually use pieces of that
> | black or pink anti-static carrier foam to hold the chips
> | where I want them to be.
>
> I would suggest the black material over the pink; the black
> material is slightly conductive, ensuring that any static
> charge on any part of its surface will slowly spread out over
> the entire thing; thus it's impossible for one spot on the
> foam to hold a charge relative to the rest of it.  The pink
> stuff works by refusing to easily accept or give up electrons
> on its surface (so it won't take a charge in the first place).
> In many situations this is just as good, but strong UV can
> cause ionisation (i.e. electrostatic buildup) in many materials
> including those inside the PIC and it's probably a good idea to
> give those ions a safe path lest they find an unsafe one (e.g.
> by breaking down the PIC's dielectric).

 Replace the foam periodically, too (The UV "Rots" it in time.)  I've
seen gang "Tray" type erasers with just crumbs left, in production
environments where they had a gang programmer & were constantly erasing
scads of 27256 EPRoms.  (Most of Us:  Every couple years;  Them:
Monthly.  They ran the eraser 15 hours a day or so!)  Still have 27C256Q
Eproms left from there <G>

 Anyone ever tried sponge metal for this job?  I've wondered if it'd
work (Pricey stuff last I priced it, though.  Should last forever OTOH.)

 Mark, .....mwillisKILLspamspam@spam@nwlink.com

1998\10\29@132109 by Peter L. Peres
picon face
On Wed, 28 Oct 1998, Mark Willis wrote:

>   Replace the foam periodically, too (The UV "Rots" it in time.)  I've
> seen gang "Tray" type erasers with just crumbs left, in production
> environments where they had a gang programmer & were constantly erasing
> scads of 27256 EPRoms.  (Most of Us:  Every couple years;  Them:
> Monthly.  They ran the eraser 15 hours a day or so!)  Still have 27C256Q
> Eproms left from there <G>
>
>   Anyone ever tried sponge metal for this job?  I've wondered if it'd
> work (Pricey stuff last I priced it, though.  Should last forever OTOH.)

Drape a piece of cooking aluminium foil over the foam and stick the chips
in through that. Replace foil when it resembles sieve.

Peter

1998\10\29@132113 by Peter L. Peres

picon face
On Wed, 28 Oct 1998, John Payson wrote:

> | You can
> | speed up erasure time by placing the chip erasure window
> | even closer to the UV lamp. I usually use pieces of that
> | black or pink anti-static carrier foam to hold the chips
> | where I want them to be.
>
> I would suggest the black material over the pink; the black
> material is slightly conductive, ensuring that any static
> charge on any part of its surface will slowly spread out over
> the entire thing; thus it's impossible for one spot on the
> foam to hold a charge relative to the rest of it.  The pink
> stuff works by refusing to easily accept or give up electrons
> on its surface (so it won't take a charge in the first place).
> In many situations this is just as good, but strong UV can
> cause ionisation (i.e. electrostatic buildup) in many materials
> including those inside the PIC and it's probably a good idea to
> give those ions a safe path lest they find an unsafe one (e.g.
> by breaking down the PIC's dielectric).

The real reason for which parts in an UV eraser should have the pins
shorted is, that any charge stored inside the chip may flow in unexpected
ways and polarize chip pins in unexpected ways. I've never seen such a
thing happen but some people claim it could do something.

Peter

1998\10\29@132117 by Peter L. Peres

picon face
On Wed, 28 Oct 1998, John Payson wrote:

> | You can
> | speed up erasure time by placing the chip erasure window
> | even closer to the UV lamp. I usually use pieces of that
> | black or pink anti-static carrier foam to hold the chips
> | where I want them to be.
>
> I would suggest the black material over the pink; the black
> material is slightly conductive, ensuring that any static
> charge on any part of its surface will slowly spread out over
> the entire thing; thus it's impossible for one spot on the
> foam to hold a charge relative to the rest of it.  The pink
> stuff works by refusing to easily accept or give up electrons
> on its surface (so it won't take a charge in the first place).
> In many situations this is just as good, but strong UV can
> cause ionisation (i.e. electrostatic buildup) in many materials
> including those inside the PIC and it's probably a good idea to
> give those ions a safe path lest they find an unsafe one (e.g.
> by breaking down the PIC's dielectric).

Ionized air is a better conductor than the other kind of air. Ionizers are
used among other things to get rid of static buildup in places where other
methods can't be used. Ionized air also tends to purify the air by
oxydizing what there is to be oxydized (ex: organic fumes and trace
elements, such as smelly organic compounds).

Peter

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