Re: [ATM] synchronous motor and cheap inverter - tests and question.

["Bob May" <rmay@nethere.com>]

I never said that you can't use a crystal in th circuit, just
that the inverters sold don't use them.  Big difference!
It doesn't matter how you generate the frequency, nor to that
degree how accurate the frequency is in such devices.  For the
manufacturers, a crystal is an expensive part to put on a cheap
device like that and they'd rather not when there is no need ofr
that much accuracy in the frequency of the device as it isn't
going to be used for any devices like a clock which often needs
to have the line frequency accurate as can be.  A simple
resitstor and a capicator do more than well enough for the job
along with the silicon needed to do the oscillation generator of
the devcice.  The cost is the same in terms of the silicon as
there still is usually two pins for the crystal as there are for
the R-C network and the silicon doesn't care really how much work
needs to be done inside as the cost of the layout is the same for
each method.
I'll note that the manufaccturers complain enough that they have
to put a transformer on the board and the smaller it is, the
better off the manufacturer feels about that.  This is part of
why higher and higher frequencies are being used ot convert the
low voltage to a higher voltage as the transformers get smaller
with the higher frequiencies as well as the caps needed in the
circuit.
They'd rather put in a half cen't of parts rather than a
quarter's worth of a part.  can you blame them?
BTW, Epson makes a nice IC that generates all kinds of
frequencies from one crystal with a digital selection of the
division ratio desired.  That would make a nice part for a dricve
corrector but you will have to do some fancy work with other
parts to get the modified sine wave that should come out of the
device unless you do the fancier full sine wave which is not
ammendable to easy producetion at the higher powers needed by
electrical devices.  I saw one company which did a convrtor for
reomtely controlled gates which needed about two square feet of
board space to do the job where the little convertors use about
four square inches to do the same thing. effectively with the
modified sine wave idea.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net


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