John Midgley wrote:
>
> Robin wrote:
>
> >for the same price
> >and effort folks put into building their own erasers, you could buy a
> >commercial unit such as the Datarase II for around $40 or $50 with a timer.
>
> I follow threads on the subject of UV erasers (especially home-made ones)
> with some interest, since I'd like to start playing with PICs other than the
> EE variety. Being a bit of a cheapskate, and a bodger, I always look for
> ways to make stuff rather than buy it, where there seems to be a large
> difference between the cost of the parts, and the completed item. I made a
> UV exposure unit for making PCBs for 10 or 15GBPounds, which wouldn't
> be any use to a 'professional' but which does for me.
>
> However (you're not supposed to start sentences with 'however', are you?);
> I'd cheerfully pay 25 or 30GBP for this Datarase thing, but over here in
> Merrie England, people want 50GBP ($80-odd). Rather less attractive at
> that price? Especially if an amateur-capable bodge can be done for
> 20GBP.
>
> Having said that, if any English PICers know where I can find a UV eraser
> at a realistic price, please say!
>
To make an eprom eraser, just get a set of 8-watt fluorescent-light
control gear (starter and ballast), a light-proof box, interlock switch
and
a  8W hard-UV tube (253.7 nM wavelength uncoated).  The tube is
electrically
the same as an 8w white tube, but it emits shortwave UV.   The circuit,
the light-proof-ness of the box, and the operation of the interlock sw
can be tested using a harmless white tube.  Remember that shortwave UV
is biologically damaging both to the eyes and skin, so avoid exposure.
This type of UV lamp works in the shortwave UV region, the most
effective
for erasing.  This is the same as the germicidal lamps used in water
treatment, etc.  Note that soft-UV tubes (used in sunbeds, etc) may
erase
devices slowly, but not very well.

BTW, a xenon strobe can be used to erase devices.  Dataman make a strobe
eraser, which works in seconds, and can be used with the device in the
programmer!. I keep meaning to build something like that myself!

BTW, I recently succeeded in erasing 150-odd mis-programmed OTP PIC's by
baking them.  Think they won't be reliable, though!!!!!!

Hope this of use....
jim ford