CENTENT CN0182 User manual

OPERATING MANUAL
CN0182 SERVO DRIVE
3879 SOUTH MAIN STREET 714-979-6491
SANTAANA, CALIFORNIA 92707-5710 U.S.A.
0 M P A N Y

CN0182 PULSE INCREMENTAL SERVO DRIVE
This manual contains information for installing and operating the following
Centent Company product:
CN0182 Servo Drive
Centent and the Centent Company logo are trademarks of Centent Company.
Other trademarks, tradenames, and service marks owned or registered by any
other company and used in this manual are the property of their respective
companies.
Copyright ©2019 Centent Company
3879 South Main Street
Santa Ana, CA 97207
All Rights Reserved
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CENTENT COMPANY
iii
CONTENTS
GENERAL DESCRIPTION ...................................................................................1
LOCATION OF COMPONENTS..........................................................................2
GETTING STARTED.............................................................................................. 3
QUICK SETUP........................................................................................................3
THEORY OF OPERATION...................................................................................4
Main Elements..................................................................................................... 4
Auxiliary Elements ..............................................................................................5
Current Limit ........................................................................................................7
Protection Circuits............................................................................................... 8
TERMINAL BLOCK FUNCTIONS
Motor Group.......................................................................................................10
Power Supply Group ........................................................................................11
Encoder Group.................................................................................................. 12
Sine-Cosine Encoders................................................................................................14
TTL Encoders ..............................................................................................................14
Command Group............................................................................................... 15
OPTION HEADER................................................................................................ 17
System Inertia....................................................................................................17
Position Error..................................................................................................... 18
+2.5V Reference...............................................................................................18
Current Monitor ................................................................................................. 18
Fault Output....................................................................................................... 19
Reset Input.........................................................................................................20
+12 Volt Test...................................................................................................... 20
Encoder Jumper................................................................................................ 20
Ground................................................................................................................ 20
TUNING THE CN0182 SERVO DRIVE
Current Trimpot................................................................................................. 21
Gain Trimpot......................................................................................................22
Damping Trimpot...............................................................................................22
Integral Coefficient............................................................................................ 23
Servo Loop Tuning ...........................................................................................23
Interpreting Figure 12 – Optimum Damping.................................................. 27
Picking A Motor................................................................................................. 27
Motor Fundamentals......................................................................................... 28
SPECIFICATIONS................................................................................................31
FULL SCALE DRAWING....................................................................................32

GENERAL DESCRIPTION
The CN0182 is a closed-loop PID (proportional-integral-differential) positioning servo drive
that provides closed-loop control of brush-type DC servo motors. The power amplifier is an
‘H’ bridge utilizing MOSFET technology. The drive is capable of delivering up to 20 amps
of continuous current to the motor. Motion instructions are sent to the CN0182 as Step and
Direction in a pulse train format.
The CN0182 operates on a single voltage DC power supply ranging between 18 and 80 volts
DC. The power supply voltage is determined by the motor’s rated voltage. The power supply
may be regulated or unregulated.
The motor driven by the CN0182 must be equipped with an incremental encoder with either
a digital (TTL) or analog (sine-cosine) output. Analog encoders with ±1 volt outputs can be
connected directly to the CN0182. Analog encoders that do not comply with this voltage
specification may be used but will require external amplification or attenuation to interface to
the CN0182.
The CN0182 also facilitates step motor to servo motor conversions since it is controlled by a
step motor indexer, pulse generator or motion controller, like a step motor drive. The servo
motor exhibits holding torque, velocity, tracking, incremental motion and no minimum
operating speed, while retaining the advantages of a DC servo motor such as increased high
speed torque, absence of vibration and low heating. The upgrade from stepper to servo
retains the existing indexer and control software while providing all the advantages of a
closed loop servo motor system.
Torque and loop stability are controlled by trimpots built into the drive. A screwdriver is
used to set motor current and tune the servo response of the drive.
Over-temperature and under-voltage protection is also built in. Upon sensing either of these
fault conditions, the CN0182 removes power from the motor, guarding both the drive and the
motor from damage. A light emitting diode (LED) provides visual indication of the fault
condition.
The CN0182 is compact, measuring 4.75" x 4" x 0.85" (121mm x 102mm x 22mm). It comes
encapsulated in a heat conductive epoxy and encased in an anodized aluminum cover. This
results in an environmentally rugged package that resists abuse and contamination.

CN0182 PULSE INCREMENTAL SERVO DRIVE
LOCATION OF COMPONENTS
1
3
2
4
7
6
8
9
5
Figure 1
(1) MODULE
The CN0182 is encapsulated in epoxy and encased in an anodized aluminum cover.
Information is printed on the cover for the configuration of the Option Header and for the
electrical connections to the drive.
(2) MOUNTING PLATE (5) MOUNTING HOLES
The temperature of the drive must never be allowed to exceed 70°C (158°F). The Centent
HSK heat sink kit may be ordered if additional heat sinking is required. Four mounting holes
on 3.625” centers are provided to secure the drive to the heat sink or user equipment.
(3) TERMINAL BLOCK
A 12 position terminal block provides direct electrical connections to the drive; just strip the
wire, insert and tighten the screw. The motor, power supply, encoder and indexer interface
are accessed through this connector. The function of each terminal is printed on the cover
adjacent to the screw. Do not over-tighten the screws, a torque-limit driver is recommended.
(4) OPTION HEADER
The user must configure this header for encoder type and system inertia. Position Error, Fault
output and Reset input functions are also available. Header pin assignments are printed on
the cover of the drive.
(6) FAULT LED
The LED (light emitting diode) is a visual indicator of the Fault Output. The LED is on when
the Fault Output pin on the Option Header is active.
(7) DAMPING TRIMPOT (8) GAIN TRIMPOT (9) CURRENT TRIMPOT
These built-in trimpots are for setting motor current and tuning the servo response of the
drive. Use a small screwdriver to turn the trimpots. Do not over-torque the trimpots.
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GETTING STARTED
Five things are needed to construct a complete closed-loop servo drive system:
1. CN0182 Drive
2. Permanent magnet brush-type DC servo motor
3. Dual channel encoder (TTL or sine-cosine type)
4. DC power supply
5. Step and Direction pulse source (Indexer)
QUICK SETUP
The following steps will ensure a successful installation:
•Choose a motor adequate in size for the application
•Mount the desired encoder to the motor
•Choose a power supply with a voltage equal to the motor’s rated voltage and a
current capability equal or greater than the application will require
•Turn the CN0182 Current Trimpot completely clockwise (CW)
•Turn the CN0182 Gain Trimpot to the 9 o’clock position
•Turn the CN0182 Damping Trimpot to the 11 o’clock position
•Jumper the CN0182 System Inertia pins on the Option Header to Low Inertia
•Connect the power supply, encoder and motor to the CN0182 Drive
•Apply power temporarily and observe the motor and the Fault LED
•If the motor jumps and the Fault LED lights, reverse the motor leads
•Connect the Step And Direction source (Indexer) to the CN0182 Drive
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CN0182 PULSE INCREMENTAL SERVO DRIVE
THEORY OF OPERATION
The block diagram in Figure 2 shows the components of the CN0182 servo drive.
8 BIT D/A
CONVERTER
COMMAND POSITION
POSITIONFEEDBACK
U/D COUNTER
DECODER
TTL/ANALOG
PROCESSOR
PID
FILTER
OPTICAL
ISOLATORS
+5V
GENERATOR
POSITION
ERROR
CURRENT
SENSE CURRENT
TRIMPOT
CURRENT
MONITOR
RESET
INPUT
FAULT
OUTPUT
UNDER-VOLTAGE
DETECT CIRCUIT
PWM
SHUT
DOWN
FAULT
LATCH
U/D COUNTER
QUADRATURE
(X4)
ANALOG SLOPE
PROCESSOR
ENCODER
JUMPER
+5V
GAIN
TRIMPOT
OVER-CURRENT
DETECT CIRCUIT
OVER-TEMPERATURE
DETECT CIRCUIT
TO
PWM TO PWM
TO
PWM TO PWM
TO FETS
MOSFET
BRIDGE
LEVEL
SHIFT
CIRCUIT
-5V
GENERATOR
DAMPING
TRIMPOT
POSITION
LIMIT CIRCUIT
ERROR
3
2
2
1
4
12
11
10
10
5
5
6
6
7
7
8
9
9
Figure 2
MAIN ELEMENTS:
The Command Position U/D Counter is updated by the Step and Direction inputs passed
through the Optical Isolators. The Position Feedback U/D Counter is updated from the
Feedback Encoder. The difference between the two is the Position Error and is applied to the
8 Bit D/A Converter.
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The PID Filter separates this signal into its proportional, integral and differential
components. The proportional and differential components have adjustable gain, set by the
Gain and Damping Trimpots. The integral component has a fixed gain. The trimpots control
loop stability; their settings are determined by motor and load properties. The PID
components are summed and applied to the Pulse Width Modulator (PWM). The PWM
converts the PID Filter output voltage into a digital form suitable for a switching amplifier.
The MOSFET Bridge is a high power (80 volts, 20 amps) switching amplifier that drives the
motor.
AUXILIARY ELEMENTS:
The TTL/Analog Processor processes the quadrature encoder inputs through the Quadrature
Decoder into a form usable by the drive. It accepts either TTL digital encoders or analog
sine-cosine encoders depending on the settings of the Encoder Jumper on the Option Header.
If a sine-cosine encoder is selected, the TTL/Analog Processor also passes data to the Analog
Slope Processor. The Analog Slope Processor uses the sine and cosine waveforms to
interpolate position between encoder counts. The interpolation signal is summed with the
Position Error to form a continuous, smooth position error, as shown in Figure 3.
COSINE
CHANNEL
SINE
CHANNEL
SLOPE
PROCESSOR
OUTPUT
D TO A
OUTPUT
10 mV
PEAK TO PEAK
(10 mV STEP)
(+/- 1 VOLT)
(+/- 1 VOLT)
COMPOSITE
FEEDBACK
POSITION
1 INCREMENT
OF MOTION
Figure 3
The use of a sine-cosine encoder has significant advantages over a digital encoder. Because a
digital encoder can only update the Command Position U/D Counter on the encoder signal
edges, the motor position “bounces” between the two adjacent encoder counts when no step
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CN0182 PULSE INCREMENTAL SERVO DRIVE
pulses are being sent. This results in an audible squeal and a vibration equal to one encoder
count. Since a sine-cosine encoder signal contains continuous position information between
encoder counts, the motor will be absolutely still when no step pulses are being sent.
At low speeds where the motion is still incremental (move one step, stop and wait for the
next step), a sine-cosine encoder will result in much smoother operation since each step will
be better damped.
A sine-cosine encoder makes it possible to position the motor to any location, not just the
encoder count edge locations. A 500 count digital encoder results in 2000 resolvable
locations (0.18 degree resolution), but if a 500 line sine-cosine encoder is used, there is also
additional position information between each count location. This interpolated position
feedback can be utilized by driving the Position Error pin on the Option Header (Pin 2).
One example, shown in Figure 4, multiplies the encoder line count by a factor of ten. A 500
line sine-cosine encoder has the equivalent resolution of a 5000 count digital encoder. This
results in 20,000 resolvable locations. The user’s U/D Counter divides the Step count by 10
and acts as a low resolution D/A Converter. The full-range output of the D/A is scaled to
equal a one count Position Error step (10 mV), and is summed with the Position Error
voltage.
POSITION ERROR
(PIN 2)
U/D
CL Q0 Q1 Q2 Q3
R1 R2 R3 R4
R5
UP/DOWN
DECADE
COUNTER
CO
VSS
VDD
R5 = 2.2MEG
R4 = 24.9K
R3 = 49.9K
R2 = 100K
R1 = 200K
GROUND
DIRECTION
INDEXER
CN0182
STEP
ENCODER GROUND
CHANNEL A
CHANNEL B
ENCODER +5 VDC
DIRECTION
STEP PULSE
+5 VOLTS DC
13579
46810
2
6
7
8
9
10
11
12
Figure 4
A second example, illustrated in Figure 5, positions a servo motor using a relatively coarse
(inexpensive) sine-cosine encoder and does the fine positioning by driving the Position Error
Pin either manually using a joystick or a potentiometer, or automatically with a user’s closed
loop signal. This is represented by P1 in Figure 5. The required manual adjustment range can
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be set from one encoder count to a maximum of ±128 encoder counts, depending on the
value of the Scaling resistor. In either case, the adjustment sensitivity has infinite resolution.
+2.5 VOLTS
GROUND
R1
P1
P1 = ADJUSTMENT POTENTIOMETER
(10K)
R1 = SCALING RESISTOR
(100K)
SCALINGRESISTOR
157
46810
23 9
Figure 5
Sine-cosine encoders usually require plus and minus power supply voltages for proper
operation. The CN0182 has an on-board –5 V Generator as well as a +5 V Generator to meet
the requirements of both types of encoders.
If a sine-cosine encoder is used, care must be taken to accurately adjust both channels to the
required ±1 volt signal amplitude in order to take advantage of interpolated accuracy. Follow
the encoder manufacturer’s recommended calibration procedures.
If the Position Error Pin is driven, care must be taken to keep noise out of this node. The
input impedance is 100K ohms in parallel with 100 pF. Precautions include shielding the
leads and keeping their lengths short. Use the encoder power supply ground (Terminal 6) as a
common for external circuitry. Do not put any capacitors on the Position Error Pin.
Failure to follow these precautions will result in unstable operation and probable Fault
Protect shutdown.
CURRENT LIMIT:
Motor current is sensed across a Current Sense resistor located at the power supply end of the
MOSFET Bridge. The Current Sense resistor serves the dual purpose of sensing motor
current for current limiting in normal operation as well as sensing short circuit conditions for
the protection circuit.
Because of the location of the Current Sense resistor, the voltage is passed through the Level
Shift Circuit to reference it to ground. The motor current is available at the Current Monitor
Pin on the Option Header (Pin 5). The scale is 10 amps per volt.
Motor current is limited on a pulse by pulse basis by the PWM. The Current Trimpot located
on the side of the drive sets the current limit. The range is from zero to 20 amps. Generally,
the current should not exceed the motor’s rated stall current. Setting the current limit lower
will limit the motor’s available torque and thus its ability to follow Step Pulse commands.
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CN0182 PULSE INCREMENTAL SERVO DRIVE
PROTECTION CIRCUITS:
The CN0182’s response to any fault condition is to turn-off the power transistors that drive
the motor and turn on the Fault Led and the Fault Output Pin on the Option Header (Pin 6).
A major part of the protection loop is the Fault Latch. Its function is to “remember” even
momentary fault conditions, such as a short-circuit, and keep the drive in the protected “off”
state until it is reset by the Reset Input (Pin 7) or the power supply is recycled. All fault
conditions except under-voltage, which is handled by the Under-Voltage Detect Circuit, pass
through the Fault Latch. The fault conditions are:
•Over Current
The Over-Current Detect Circuit monitors the current passing through the drive. When
excessive current occurs, the Fault Latch is set. This will occur if the motor leads short
together or to ground. Normal operation of very high current motors will not set the
Fault Latch because the Current Trimpot limits operating current to 20 amps, which is
below the Over Current Detect trip point.
•Over Temperature
The Over-Temperature Detect Circuit monitors the drive’s temperature. If the
temperature of the drive exceeds 70°C, the circuit sets the Fault Latch. This might
occur if the motor operates continuously at high currents, the drive is poorly heat-sunk
or the ambient temperature is very high. If the cause is high motor current, consider the
possibility the motor may also be overheating.
The protection provided by Over Temperature Detect Circuit is not designed as a
substitute for adequate heat sinking. Repeatedly allowing the drive to overheat and trip
the Fault Latch will cause thermal stress that may eventually lead to failure of the drive.
Under no circumstances allow the temperature of the CN0182 to reach 70°C. For very
high current applications, a fan may also be necessary to provide forced air circulation
to the heat sink.
The HSK heat sink kit is available to lower the operating temperature of the drive. The
kit consists of heat sink, side rails and screws to secure the drive and the side rails. The
side rails are reversible, allowing the two mounting configurations shown in Figure 6.
Contact Centent Company to order the HSK heat sink kit.
side rails
may be
reversed
Figure 6
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•Position Error Limit
The Position Error Limit Circuit monitors the difference between the command position
and the actual motor position. If this difference exceeds ±128 counts, the servo lock is
considered broken and the position can not be recovered. The result would be a
runaway motor and possible damage to system components. Before this condition is
reached, the Position Error Limit Circuit sets the Fault Latch, shutting down the drive.
Possible causes of a Position Error Limit trip are many; the most common, and their
remedies are:
1. Unstable Loop
Improperly set Gain and Damping trimpot settings are the causes here. This generally
shows up during the initial setup phase. If the damping setting is too low, the motor
will begin to oscillate. When the oscillation amplitude reaches ±128 counts, the
CN0182 will shut down. Increase the damping setting and try again. If the gain setting
is to low, the drive will be sluggish in responding and an error approaching ±128
counts can develop. Increase the gain setting slightly and try again.
2. Broken Loop
The CN0182 is part of a closed-loop system. The CN0182 drives the motor, the motor
turns the encoder and the encoder sends feedback information back to the CN0182,
completing the loop. Any malfunction in this loop will result in a position error and a
protective shutdown. Verify that the encoder connections to the drive are correct and
that there are no breaks in the wiring or terminals.
3. Insufficient Torque At High Speed
DC motor torque is at a maximum at zero speed (stall torque) and linearly decreases to
zero at the motor’s maximum speed (no-load speed). Consequently, the motor’s ability
to provide torque decreases as speed increases. The options here are to increase the
power supply voltage or use a motor with a higher no-load speed.
Another possible cause may be the frequency limit of the encoder. Many encoders
have a maximum frequency of 100 kHz, or 400,000 counts per second. If a high line
count encoder is used at high speed, this limit may be exceeded. For instance, a 2500
line encoder would be at this limit at 2400 RPM (60 x 100,000 / 2500).
4. Insufficient Torque At Low Speed
Motor torque is directly proportional to motor current. If the motor is unable to carry a
load at low speed, check to see if the Current Trimpot is set too low. If the motor’s
stall current is less than 20 amps, setting the Current Trimpot beyond the stall current
will not help, since it is the motor and not the drive that limits current. The options
here are to get a higher stall current motor (up to 20 amps) or a motor with a higher
torque constant.
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CN0182 PULSE INCREMENTAL SERVO DRIVE
TERMINAL BLOCK FUNCTIONS
Wire of 16-22 gauge is recommended for the connections made to the CN0182. The
insulation should be stripped back 0.25 inches before inserting the wire, to assure good
contact with the connector. No additional terminals or connectors are required on the ends of
the wire. Care must be taken not to damage the screw terminals by over tightening. If
possible use a torque-limiting driver, set to a maximum of 4.5 lb.- in.
The 12 position Terminal Block is grouped by function; the four groups are Motor Group,
Power Supply Group, Encoder Group and Command Group. A detailed description of each
follows:
MOTOR GROUP TERMINALS 1-2
Terminal 1 is the "plus" motor
connection and Terminal 2 is the
"minus" motor connection.
The motor will rotate clockwise when the Direction Input (Terminal 10) is at a logical “0”
(low).
The motor must be a permanent magnet, brush-type DC servo motor. Preferred motors have a
laminated iron armature. The drive requires a minimum inductance of 500 μH. Pancake, cup
and other ironless armature motors have very low inductance (less than 500 μH) and
consequently will have excessive ripple current. This ripple current will cause considerable
motor heating. If these type motors are used, insert a 500 μH inductor in series with the
motor. Make sure the inductor is rated for the maximum current the motor will carry.
The output is a pulse-width modulated (PWM) 20 kHz waveform with voltage amplitude
equal to the power supply voltage. The maximum output current of the drive is ±20 amps.
If motor wires longer than 3 feet are required, use a shielded cable. This will limit the amount
of radiated electrical noise that could interfere with other equipment. A three conductor,
shielded cable is recommended. The suggested wiring configuration is shown in Figure 7.
CHASSIS GROUND
SHIELDED CABLE
MOTOR
CASE
+ MOTOR
- MOTOR
SUPPLY GROUND
1
2
3
Figure 7
Two of the wires go to the motor terminals while the third connects to the motor’s case at
one end and to the CN0182’s Supply Ground (Terminal 3) at the other.
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The shield should be connected to the chassis ground at one end only! This way the
shield cannot conduct and radiate ground-loop currents.
POWER SUPPLY GROUP TERMINALS 3-4
The CN0182 operates on a single voltage DC
power supply, ranging between 18 VDC and
80 VDC.
The power supply may be regulated or unregulated. If the power supply is regulated, it must
have at least 1000 μf of capacitance on the output.
Terminal 4 is the positive input and Terminal 3 is the ground return. The choice of power
supply voltage and current is based on the motor selected. The voltage should be high
enough to run the motor at the maximum speed required by the application. A good first
choice is a power supply voltage equal to the motor’s rated voltage plus two volts to account
for the losses in the drive.
The current rating of the power supply must be sufficient to meet the torque requirements of
the application. A good choice is a power supply with a current rating equal to the motor’s
stall current.
Most motors have a stall current ten times higher than the motor’s continuous rated current.
The continuous rated current is based on the motor’s ability to safely dissipate heat. However
for short periods of time, while accelerating or decelerating, the motor can handle much
higher currents without harm. The power supply must be rated to meet this temporary current
draw.
This makes the power supply up to ten times larger than it otherwise would need to be, since
conventional power supplies cannot deliver current ten times their rated continuous current.
One possible way around this problem is shown in Figure 8.
The power supply transformer, rectifiers and filter capacitor are sized to provide current that
is slightly greater than the motor’s continuous rated current. A rechargeable battery,
(preferably nickel-cadmium), with a voltage rating a little below the power supply’s voltage
is placed across the power supply output through a diode.
While the motor is drawing current less than the continuous rated current, the diode is
reverse biased and no current flows from the battery.
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CN0182 PULSE INCREMENTAL SERVO DRIVE
D1
D2
D3
D4 D5
B1
C1
T1
115 VAC
BATTERY
CHARGER
SUPPLY GROUND
+ 18 to 80 VOLTS DC
B1 = NICKEL-CADMIUM BATTERY
D5 = BATTERY DIODE
C1 = FILTER CAPACITOR
T1 = POWER SUPPLY TRANSFORMER
D1, D2, D3, D4 = BRIDGE RECTIFIER
3
4
+
+
Figure 8
When the motor begins to draw current in excess of the power supply rating, the power
supply voltage begins to sag and the diode begins to conduct current from the battery,
supplying the temporary current necessary for acceleration. Once the load eases, the power
supply voltage rises and turns off the current from the battery. The trickle-charger restores
the charge drained from the battery.
High currents through long, light gauge wires will result in a significant voltage drop. This
voltage drop can be enough to cause the CN0182 go into Under-Voltage Protect and reset.
This will then cause the motor to develop a Position Error Limit and Fault Output. The result
is the motor will have less performance than expected since it would have to be accelerated
more slowly to avoid drawing this level of current.
IMPORTANT!
Power supply wires must be heavy (16 gauge maximum) and as short in
length as possible. This is especially true for large, high current motors.
ENCODER GROUP TERMINALS 5-9
Terminals 5 through 9 form the encoder interface, providing closed loop feedback to the
drive. The CN0182 provides regulated 5 volt outputs to power digital or analog encoders.
Analog encoders normally
require a bipolar power
supply while digital
encoders will generally use
only a +5 volt supply.
Terminal 9 is the +5 VDC
encoder power supply
output required by digital
(TTL) quadrature encoders.
The output provides a
maximum of 100 mA of
current. Most TTL encoders
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require substantially less power supply current to operate.
Terminal 5 provides a –5 VDC power supply @ 50 mA maximum. This allows the CN0182
to interface to analog (sine-cosine) encoders. These types of encoders need bipolar (+ and -)
power supplies. Since most encoders use the +5 volt supply to power their LEDs, the –5
VDC current rating of 50 mA is more than adequate.
Terminal 6 is the encoder ground. Use this terminal for the encoder return and ground shield.
Do not use Terminal 3 for encoder return. Terminal 6 connects to a “quiet” ground internally
while Terminal 3 has considerable ground noise that would compromise the noise immunity
of the encoder signal lines and cause erratic operation of the motor.
Terminals 7 and 8 are the channel inputs from the encoder. The inputs can be either TTL
(zero VDC, +5 VDC) levels or analog ±1 volt amplitude sine-cosine inputs. The Encoder
Jumper on the Option Header (pins 9-10) selects between digital and analog encoder
operation. With no jumper in place the inputs must be TTL level signals; with a jumper
present the inputs are analog.
For analog sine-cosine encoders the CN0182 requires the channel outputs to be ±1 volt in
reference to ground. Encoders that do not comply will require external amplification or
attenuation to interface to the CN0182.
Analog and digital encoders may be powered directly from the CN0182 if they
draw less that 100mA @ +5V and 50 mA @ -5V. Encoders requiring higher
voltage or current must be operated by external power supplies.
A special TTL encoder case occurs if the encoder outputs are open collector. Open collector
outputs must have pull-up resistors in order to function. Figure 9 shows how these resistors
are to be connected.
ENCODER +5 VDC
CHANNEL B
CHANNEL A
470
470
7
8
9
Figure 9
The CN0182 performs a "times 4" decoding, resulting in a resolution four times greater than
the line count of the encoder. As an example, a 1000 count per revolution encoder will result
in 4000 positions per revolution.
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CN0182 PULSE INCREMENTAL SERVO DRIVE
While more common, digital (TTL) encoders have the drawback of "hunting" between
adjacent encoder counts. This manifests itself as buzzing or humming, and is most noticeable
when the motor is stopped. Analog encoders avoid this by providing continuous position
information between encoder counts. The result is silent and stable operation while the motor
is stopped.
The CN0182 has been tested with numerous TTL and analog type encoders. Below are
several encoders that have performed satisfactorily with the CN0182. This is by no means a
complete list of acceptable encoders.
SINE - COSINE ENCODERS
COMPUTER OPTICAL
PRODUCTS DYNAMICS RESEARCH CORP.
MODEL CP-800-5000-F T23DA4EDB2V-1000
LINES 5000 (20,000 counts / rev) 1000 (4000 counts / rev)
CN0182 ENCODER LEAD WIRE ENCODER LEAD WIRE
Terminal 5 WHITE/BROWN (stripe) BLUE
Terminal 6 GRAY/WHITE (stripe) BLACK
Terminal 7 WHITE/ORANGE (stripe) WHITE
Terminal 8 BLUE/WHITE (stripe) GREEN
Terminal 9 BROWN/WHITE (stripe) RED
TTL ENCODERS
HEWLETT PACKARD BEI MOTION SYSTEMS
CO.
MODEL HEDS-5500 A06 MOD5540-25-500
LINES 500 (2000 counts / rev) 500 (2000 counts / rev)
CN0182 ENCODER TERMINAL ENCODER TERMINAL
Terminal 5
Terminal 6 PIN 1 PIN 1
Terminal 7 PIN 2 PIN 2
Terminal 8 PIN 3 PIN 3
Terminal 9 PIN 4 PIN 4
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COMMAND GROUP TERMINALS 10-12
The Step Pulse, Direction and +5
VDC inputs form the motion
command interface to the
CN0182.
The motor will move one encoder increment for each step pulse received. The motor moves
in a clockwise rotation if the Direction Input is low at the moment of the step pulse input and
counter-clockwise if the Direction input is high.
The inputs are optically isolated from the rest of the drive circuitry to provide noise
immunity. The high currents, voltages and fast edge times of the motor amplifier generate
considerable electrical noise that would create problems with the indexer logic circuits.
Optical isolation keeps this noise from getting into the indexer.
An indexer or other pulse source generates Step and Direction input to the drive by sinking
the cathodes of the optical isolator LEDs to ground. The external +5 Volts DC used to power
these diodes must be provided by the indexer or pulse source.
The CN0182 uses high-speed opto-isolators that can pass pulse trains up to 1 MHz. It is
necessary that the Step and Direction Inputs have rise and fall times under 50 nano-seconds
to avoid false steps and erratic operation. The opto-isolator driver current sink capability
must be at least 16 mA. This requirement is easily met with standard TTL or 74HC bus
drivers.
IMPORTANT!
Do not run the Command Group wires in a common wiring harness with the Motor
Group wires. Doing so will result in erratic motor behavior because capacitive
coupling of motor waveforms into the Step and Direction input lines would cause
false steps.
If it is necessary to run Command, Encoder or Motor wires longer than 3 feet use shielded
cables. This is particularly important for the Motor wires.
Terminal 10 is the Direction Input. The state of this input is sampled on the rising edge of the
Step Input and determines the direction in which the increment of motion will be taken. If the
Direction Input is a logical “0”, then the step will be in the clockwise direction. If it is a
logical “1”, (+5 VDC or open), then the step will be taken in the counter-clockwise direction
Terminal 11 is the Step Input. A rising edge (0 to +5 VDC) on this input will result in one
increment of motion. The size of this increment is determined by the encoder resolution; a
500 line encoder will yield 0.18 degrees of motion (360°/ 500x4 = 0.18°). The direction of
15

CN0182 PULSE INCREMENTAL SERVO DRIVE
motion is set by the state of the Direction Input at the time of the Step Input edge. The device
connected to Terminal 11 must be capable of sinking 16 mA of current.
Terminal 12 is the +5 VDC terminal. This input is connected internally to the common
anodes of the Step Pulse and Direction opto-isolator LEDs. By using a separate power
supply, provided by the indexer or pulse generator, electrical isolation between the CN0182
and indexer is maintained.
Terminal 12 is not a 5 Volt output from the CN0182. A separate, external 5-Volt supply must
be connected to this terminal. Do not connect Terminal 12 to Terminal 9. A suggested hook-
up for the Command Group is shown in Figure 10.
+5 VOLTS DC SUPPLY
STEP PULSE OUTPUT
DIRECTION OUTPUT SHIELDED CABLE
INDEXER CN0182
GROUND
DIRECTION
STEP PULSE
+5 VOLTS DC
10
11
12
Figure 10
If power supply voltages higher than 5 VDC must be used the Step Pulse and Direction
inputs will each require external series resistor to limit the current to the opto-isolators to a
maximum of 10 milliamps. Do not connect a single resistor to Terminal 12 to limit current;
two resistors are required, one to Terminal 10 and one to Terminal 11 (see Figure 11). In this
example a 12-volt supply and 750 ohm external resistors are shown.
750
750
+12 VOLTS DC SUPPLY
STEP PULSE OUTPUT
DIRECTION OUTPUT
INDEXER CN0182
+5 VOLTS DC
STEP PULSE
DIRECTION 10
11
12
Figure 11
Resistor values for common power supply voltages are shown below:
Power Supply External Resistors
12 volts 750 Ω
18 volts 1.3 KΩ
24 volts 2.0 KΩ
16