l
5
,708.339
7
comprises a
pair
of
single-phase.
doughnut
transformers
T1
connected
in
parallel.
The
supply
or
primary
circuits
of
transformers
T1
are
connectable
to
any
suitable
source of
electricity
such
as
115
volt.
60
cycle.
single-phase
electric
ity.
The
energy
receiving
or
secondary
circuits
of
transform
ers
T1
are
connected
through
one
or
more
recti?er
bridge
circuits
B1
and
B2
and
capacitors
C6
and
C7
to
a
pair
of
controlled
voltage
power
terminals.
one
of
which
forms
a
source
of
direct
current
maintained
at
positive
34
volts
and
the
other
a
source
of
direct
current
at
negative
34
volts.
An
eight
volt
direct
current
power
supply
is
illustrated
in
FIG.
8
of
the
drawing.
The
eight volt
power
supply
com
prises
a
pair
of
terminals
connectable
to
the
positive
and
negative
34
volt
terminals
of
power
supply
90
through
resistors
R13
and
R24
to
positive
and
negative
8
volt
terminals.
A
pair
of
diodes
Zenier
D15
and
D20
are
provided
in
the
8
volt
power
supply
between
resistors
R13
and
R24
and
a
ground
terminal.
The
recti?ers
in
bridge
circuits
B1
and
B2
are
conven
tional
MB
352
recti?ers.
Capacitors
C6
and
C7
are,
for
example
33,000
UF
capacitors.
Resistors
R13
and
R24
are
470
ohm.
2
watt
resistors.
The
34
volt
and
8
volt
power
supplies
illustrated
in
FIGS.
7
and
8
are
of
conventional
design
and
form
no
part
of
the
present
invention
except
in
combination
with
the
other
elements
of
the
control
circuit.
It
should
be
appreciated
that
many
other
DC
power
supplies
may
be
used
in
lieu
of
those
illustrated
in
the
drawing.
Encoders
Conventional
multichannel
incremental
optical
encoders
E1, E2.
E3
and
B4
are
mounted
on
the
shaft
of
each
motor
M1.
M2.
M3
and
M4,
respectively.
The
encoders
E1-E4
are
high
resolution
incremental
optical
devices
which
include
an
encoder
body,
a
metal
code
wheel and
emitter
end
plate.
An
LED
source
and
lenses
transmit
collimated
light
from
the
emitter
diode
through
a
precision
metal
code
wheel
and
phase
plate
into
a
bifurcated
detector
lens
(not
shown).
The
light
is
focused
onto
pairs
of
closely
spaced
inte
grated
detectors
which
output
two
square
wave
signals
in
quadrature
and
an
optional
index
pulse.
HEDS-6000
series,
two
and
three
channel
incremental
optical
encoder
lcits
are available
from
Hewlett
Packard
of
Palo
Alto.
Calif.
A
standard
selection
of
shaft
sizes
and
resolutions
between
192
and
1024
cycles
per
shaft
revolu
tion
are
available.
The
part
number
for
a
standard
two
channel
encoder
is
BBS-6000.
while
that
for the
three
channel
device,
with
index
pulse,
is
BEDS-6010.
The
encoder
devices
are
typically
used
for
printers.
plotters,
tape
drives.
positioning
tables,
automatic
handlers,
robots.
and
other
servo
loop
applications.
Speci?c
details
of
construc
tion
of
the
incremental
optical
encoder
can
be
found
in
Hewlett Packard
Publication
No.
5954-8420
(3187)
which
is
incorporated
herein
by
reference.
The
incremental
shaft
encoder
operates
by
translating
the
rotation
of
a
shaft
into
interruptions
of
a
light
beam
which
are
then
output
as
electrical
pulses.
The
light
source
is
a
light
emitting
diode
collirnated
by
a
molded
lens
into
a
beam
of
parallel
light.
An
emitter
end
plate
contains
two
or
three
similar
light
sources,
one
for
each
channel.
The
code
wheel
is
a
metal
disc
that
has
N
equally
spaced
slits
around
its
circumference.
An
aperture
with
a
matching
pattern
is
positioned
on
a
stationary
phase
plate,
The
light
beam
is
transmitted
only
when
the
slits
in
the
code
wheel
and
the
aperture
line
up;
therefore.
during
a
complete
shaft
revolution. there
will
be
N
alternating
light
and
dark
periods.
25
30
45
55
8
A
molded
lens
beneath
the
phase
plate
aperture
collects
the
modulated
light
into
a
silicon
detector.
The
encoder
body
contains
the
phase
plate
and
the
detec
tion
elements
for
two
or
three
channels.
Each
channel
consists
of
an
integrated
circuit
with
two
photo-diodes
and
ampli?ers.
comparator,
and
output
circuitry
(not
shown).
The
apertures
for
the
two
photo-diodes
are
positioned
so
that
a
light
period
on
one
detector
corresponds
to
a dark
period
on
the
other.
The
photo-diode
signals
are
ampli?ed
and
fed
to
a
comparator
whose
output
changes
state
when
the
difference
of
the
two
photo
currents
changes
sign.
The
second
channel
has
a
similar
con?guration
but
the
location
of
its
aperture
pair
provides
an
output
which
is
in
quadrature
to
the
?rst
channel
(phase
difference
of
90°).
Direction
of
rotation
is
determined
by
observing
which
of
the
channels
is
the
leading
waveform.
The
outputs
are
'I'I'L
logic
level
signals.
The
motion
sensing
application
and
encoder
interface
circuitry
will
determine
the
need
for
relating
the
index
pulse
to
the
main
data
tracks.
A
unique
shaft
position
is
identi?ed
by
using
the
index
pulse
output
only
or
by
logically
relating
the
index
pulse
A
and
B
data
channels.
The
index
pulse
can
be
uniquely
related
to the
A
and
B
data
tracks
in
a
variety
of
ways.
Statewidth,
pulse
width
or
edge
transitions
can
be
used.
The
two
square
wave
signals
in
quadrature
of
channels
A
and
B
and
a
5
volt
supply
input
are
delivered
through
a
10-pin
connector
to
a
corresponding
decoder
D1. D2.
D3
or
D4
mounted
on an
auxiliary
board.
as
illustrated
in
FIG.
7
of
the
drawing.
Tines
connecting
encoders
E2
to
a decoder
D2
are
illustrated.
Encoders
E3
and
B4
are
similarly
con
nected
to
decoders
D3
and D4.
Decoders
Quadrature
decoders
D1-D4
are
CMOS
(complimentary
metal-oxide
semiconductor)
integrated
circuits
that
perform
the
quadrature
decoder,
counter.
and
bus
interface
functions.
“HTCL-ZOOO,"
commercially
available
from
Hewlett
Packard,
quadrature
decoder/counter
interface
IC
decoder
interfaces
an
encoder
to
a
microprocessor
and
is
designed
for
use
in
digital
closed
loop
motion
control
system
and
digital
data
input
system.
The
decoder
includes
a
4X
quadrature
decoder.
a
binary
upldown
state
counter
and
a
16-bit
bus
interface.
A
Schmitt
triggered
CMOS
input
and
input
noise
?lters
are
incorpo
rated
in
the
device.
Further
information regarding
the
quadrature
decoder!
counter
interface
IC
for
interfacing
to
Motorola
and
Intel
microprocessors
can
be
found
at
page
1-61
through
page
l-76
of
Hewlett
Packard
Publication
for
“HCl‘L-2000.”
“HCI'L-2016,” “HCI'L-2020.”
Decoders
Bil-D4
have
pins
for a
channel
A
and
channel
B
Schmitt-trigger
inputs
which
accept
the
outputs
from
quadrature
encoders
131-134.
The
two
channels
are
prefer
ably
90°
out
of
phase.
Controller
The
system
is
controlled
by
a
computer
95,
illustrated
in
FIG.
6.
which
receives
and
stores
a
set
of
instructions
and
then
acts
upon
the
instructions
in
a
predetermined
and
predictable
fashion.
A
microprocessor
96
is
attached
to a
printed
circuit
board
into
which
a
thin
layer
of
metal
has
been
applied
and
then
etched
away
to
form
traces.
The
electronic
components
of
the
central
processing
unit
are
attached
to
the
board
with
solder
so
that
they
can
change
electronic
signals
through
the
etched
traces
on
the
board.