Olin,

On Wed, 22 Dec 2004 07:51:47 -0500, Olin Lathrop wrote:

> The wall wart is surprisingly cheap.  It costs $1.52 in quantities of o=
nly 10. =20
> This is one reason I picked that particular wall wart. =20

Sadly that doesn't help those of us not in North America - I have been lo=
oking for a 15VAC supply here, and=20
they are rather rare - 99% of the wall-warts are DC output, and 15V isn't=
 one that's well covered.  I tried a=20
9-0-9 250mA transformer that I had handy, but the DC ending up on the 780=
5 measured 31V!  I eventually settled=20
on a large wall-wart that has switchable taps, 15V being the highest.  Fo=
r other Brits: it's N57AT from=20
Maplin, and costs =A37.99 (say 10x the price you mentioned above, at the =
current exchange rate). =20

How close does the unregulated DC have to be to 17V?  With no chips on th=
e board and the PSU set to 15V it's=20
reading 22.5V.

>I figured that
> having an option to remove it would cost me more in logistics than to j=
ust
> pay for it.  However, I haven't figured out what to do about countries =
that
> don't have US compatible wall power.  Maybe include a 1.3mm plug instea=
d so
> that they can wire up easily to their own wall wart or other power supp=
ly.

That sounds like a good move - 1.3mm isn't that common and having it hand=
y would be a Good Thing.

> Which countries have US compatible wall power?  I know the US and Canad=
a are
> the same, and I think Mexico too, and maybe Japan, but after that I hav=
e no idea.

Basically North America plus Taiwan, and Japan sort-of.  I believe Japan =
uses the same connector, but the=20
voltage may be anywhere from 100V to 200V - sites I've looked at are a li=
ttle unclear on this.  The best=20
solution for a single international-compatible power supply is one that a=
ccepts 100-240V, 50 or 60Hz and has=20
an IEC 320 socket ("Kettle lead") so the user just has to add a cable to =
fit their own wall-socket. =20
Unfortunately they tend to be switched-mode devices and you won't get one=
 of these for $1.52! =20
=20
>...<

> A year ago I added up the parts
> cost if I were to buy reasonable quantities from hobby places like Jame=
co,
> and I think it came to around $25 plus the circuit board.  That doesn't
> sound good compared to $60 when you don't think about the substantial
> engineering, testing, and packaging into a kit that you are getting.  T=
his
> is the thing a lot of hobbyists don't seem to get.  Just because someth=
ing
> is conceptually simple doesn't mean there isn't substantial work envolv=
ed in
> realizing it.

It never ceases to amaze me how much trouble people will go to to save a =
tiny amount of money - part of the=20
great Consumer Boom I suppose!  Some seem to think that the design effort=
 should be free... a bit like saying=20
that the aircraft was going there anyway, so why should I have to pay the=
 airfare?  :-)

Merry Christmas!


Howard Winter
St.Albans, England



--=20
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