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-----Original Message-----
it seems that it should be binary. In other
words, for every bit position,
the number should double. For instance,if it had
only one bit/switch,
then the total number of possiblities are
two...either on or off. If
it had two bits, the number of possible
combinations of on/off would
be four. You can carry this on out...8, 16, 32,
64, 128, 256, 512,
1024, 2048, etc. and see how it doubles every
time, thus all
combinations are divisible by 2 (binary). Using
your numbers, this
logic results in fractional numbers, which causes
me to wonder.
--------End Original Message-----------------


I think you are assuming there is a byte size
which determines resolution. But if I understand
correctly, the actual resolution is a matter of
physical layout. A unit can be constructed which
sends one, two, three, four or more (actually
higher) pulses per revolution. This, combined with
the gearing ratio will then determine the actual
encoder resolution.

Chuck Taylor
Losmandy wannabe & lurker

----- Original Message -----
From: <midniterider@...>
To: <Losmandy_users@...>
Sent: Monday, September 11, 2000 21:09
Subject: [Losmandy_users] Re: Encoder resolution

--- In Losmandy_users@..., "Charles Taylor"
<chucktaylor3@i...> wrote:

Hi,

-----Original Message-----
it seems that it should be binary. In other
words, for every bit position,
the number should double. For instance,if it had
only one bit/switch,
then the total number of possiblities are
two...either on or off. If
it had two bits, the number of possible
combinations of on/off would
be four. You can carry this on out...8, 16, 32,
64, 128, 256, 512,
1024, 2048, etc. and see how it doubles every
time, thus all
combinations are divisible by 2 (binary). Using
your numbers, this
logic results in fractional numbers, which causes
me to wonder.
--------End Original Message-----------------


I think you are assuming there is a byte size
which determines resolution. But if I understand
correctly, the actual resolution is a matter of
physical layout. A unit can be constructed which
sends one, two, three, four or more (actually
higher) pulses per revolution. This, combined with
the gearing ratio will then determine the actual
encoder resolution.

Chuck Taylor
Losmandy wannabe & lurker

Chuck:
The resolution of an optical encoder is determined by how many,
and how small the light/dark slots are on the wheel. My point is
that
DSC's are digital, which means they are binary, which means that
total
resolution, or any number in between, will be divisible by two.
That's why I questioned the number used previously. The resolution
that was stated could not be divided by two continuously without
fractional numbers. There are no fractions in binary. We can use
digital/binary to represent numbers in another base system, i.e.
octal, decimal, hexadecimal, or even degrees, minutes, and seconds.
Did I clear it up, or did I merely "muddy the waters"?

Bruce Inscoe


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-----Original Message-----
From: midniterider@...
<midniterider@...>
Chuck:
The resolution of an optical encoder is
determined by how many,
and how small the light/dark slots are on the
wheel. My point is
that DSC's are digital, which means they are
binary, which means that
total resolution, or any number in between, will
be divisible by two.
That's why I questioned the number used
previously. The resolution
that was stated could not be divided by two
continuously without
fractional numbers. There are no fractions in
binary. We can use
digital/binary to represent numbers in another
base system, i.e.
octal, decimal, hexadecimal, or even degrees,
minutes, and seconds.
Did I clear it up, or did I merely "muddy the
waters"?

Bruce Inscoe
****<end quote>**

Hi Bruce,

The DSC's are binary at some point in their
operation, But not in the manner you are thinking.
They are not receiving impulses from the encoders
in a byte. The pulses are received separately and
sequentially (as in a serial port) and not in a
byte (like a parallel port) which would limit
their number to 2 to the xth where x equals the
number of bits in the byte. Therefore, no matter
what ther "resolution" is at the encoder or at the
DSC, you could disconect the encoder, hook it up
to a motor and spin it for days and days and send
"billions and billions" of impulses. There is no
limit to the number of impulses. (This of course
assumes the DSC is smart enough to figure that at
360 degrees you go back to zero --- or at 24 hours
you go back to zero --- depending on which axis)

If the encoder stored up all of the pulses and
sent them in one byte then the byte size would
limit the resolution and as you said, it would
increase as two to the xth power where x equals
the number of bits in the byte (which I think is
what you are looking for)

In effect, you actually have two places where
resolution can be limited. The first is in the
physical construction of the encoder and the gear
ratio connecting it to the mount. The second limit
is set by the DSC and is determined by how big a
turn it will register for every pulse. If the DSC
were to interpret every pulse as indicating a one
degree turn, then you would only have a resolution
of one degree. If it interprets every pulse to be
a millionth of a degree, the DSC would "limit"
resolution to that level. Of course, the encoders
and gearing ratios would then have to feed it a
pulse for every millionth of a degree.

But internally (as far as the electronics go) even
through the DSC uses binary circuitry, you are
handling the pulses one by one. They are not
accumulating into bytes which would supply the
1-2-4-8-16-32-64-128... sequence you are looking
for.

Does this help? It is late at night so I am
probably not very clear.

Take care,

Chuck Taylor
lurker at large
(and if I keep eating, even more at large)

-----Original Message-----
From: Charles Taylor
<chucktaylor3@...>

Oops, Let me add a bit of clarification to my
earlier post
I wrote:
Therefore, no matter what ther "resolution" is at
the encoder or at the
DSC, you could disconect the encoder, hook it up
to a motor and spin it for days and days and send
"billions and billions" of impulses.

It should read:
Therefore, no matter what ther "resolution" is at
the encoder or at the
DSC, you could disconect the encoder FROM THE
TELESCOPE MOUNT, LEAVING IT CONNECTED TO THE DSC,
hook THE ENCODER up to a motor and spin it for
days and days and send
"billions and billions" of impulses TO THE DSC.
THE NUMBER OF PULSES WOULD NOT BE LIMITED BY BYTE
SIZE.

Thank you for your patience (This is what happens
when I write late at night after tearing apart a
couple of printers to get steppers ;-)

One Barn door mount to go please...

Chuck Taylor