Table of Contents

1.0 INPUT POWER CONVERSION
2.0 RS-232 SERIAL INTERFACE
3.0 RS-485 MULTI-DROP I/O
4.0 SAFETY INTERLOCK
5.0 LASER & PWM INTERFACE
6.0 AXIS ENCODER & LIMITS INPUTS
7.0 TRAINING ENCODERS
8.0 STEPPING MOTOR DRIVE
8.1 AXIS DRIVE SPECIFICATION SUMMARY
8.2 CONNECTING MOTORS
9.0 INDICATORS
A.0 USER +5V POWER
 

1.0 INPUT POWER CONVERSION

    The SS4544 system has an auto switching input, allowing for input
voltages in the range of 90 to 265 vac 50-60 hz. The input is internally
fused so the fuse is not normally available to the user. A built in line
filter isolates the line from internal high frequency switching noise. A
built in transorb protects the system from momentary line transients.
Input AC power is converted to an internal 250 to 370 volt DC supply.
This is then converted via an isolated flyback switching regulator which is
synchronized with the motion control system chop rate to eliminate noise
effects. The output of the regulator produces internal system voltages of
+44v, +6v, and -12v. Linear regulators then make +12v, +5v, -5v, and a +5v
user supply.

    The power section is constructed on its own two layer printed circuit
board and connects to the motion system via a 15 pin connector.
The 44v supply is used to power the stepping motors. There is
approximately 250 watts average available, with 500 watts peak power. There
is also a shunt regulator set at 46v which absorbs dynamic breaking energy
from the motors. This can handle 500 watt peak power. An indicator lights
whenever the shunt regulator is absorbing energy. Normally this may be on
if no motors are turned on. It will be off during normal operation, but may
flash during motor deceleration.
 

2.0 RS-232 SERIAL INTERFACE

    The SS4544 system has one standard RS-232 serial interface using four
of the Standard's signals. See the mechanical section of this specification
for pin out and connector details.

RXDA - Received Data
TXDA - Transmitted Data
CTSA - Clear to Sent
RTSA - Request to Send

    The RS-232 link talks to the communication processor in the SS4544
system. For the basic system, ascii character command packets from a PC or
other controlling computer are interpreted and executed by the SS4544
system. See the software section for details.
 

3.0 RS-485 MULTI-DROP I/O

    This interface is used to connect multiple SS4544 systems together in a
common control system, and/or connect to other input and output devices,
such as keyboards, displays, sensor inputs, control outputs, etc.. The
RS-485 interface transmits information serially at up to 115 kilo baud,
differentially over twisted pair wiring. Signal levels are 0 to 5v and may
be transmitted over several thousand feet.

    Two four pin connectors are provided on the system to allow ease of
daisy chaining between equipment on the network. One pair of twisted pair
conductors is used for the RS-485 half duplex communication, while the other
pair has power for peripheral devices. The input connector has no
connection to the power, while the output does, so that power cannot be tied
between multiple SS4544 systems.

    The RS-485 interface is not opto-isolated, so care must be taken that
voltages do not appear in ground loops. Within a small machine this should
not be a problem, but if connecting over large distances, an isolation
module should be installed.
 

4.0 SAFETY INTERLOCK

    The safety interlock may be used by the system to disable the motion
system for safety reasons. There are two pins on the interlock connector,
which need to be connected together in order to enable the system. Normally
in an equipment cabinet, various interlock switches will be wired serially
in a loop, so that all interlock switches must be closed to enable the
system.

    The interlock signal is a non isolated 0 to +5v logic signal with CMOS
1.5v logic threshold. There is a 1k pull-up to +5v on the signal. If an
isolated signal is required, an opto isolator will need to installed by the
user.
 

5.0 LASER & PWM INTERFACE

    This interface has one input and one output. The output source
impedance is about 1 ohm and can drive a 50 ohm to ground termination to +5v. It
meets the drive requirements for SYNRAD laser modulation input. Current is
supplied from the user supply, so counts toward the 1 ampere maximum before
current limiting will take place. Applications include modulation of a
laser beam in coordination with axes movement, spindle speed by PWM control
of motor speed, etc.

    The input flag SPEED expects a 0 to +5v logic signal. It is a CMOS
input with TTL input thresholds of 1.5 volts. This signal is not an
opto-isolated inputs, so care must be taken for noise suppression, and
precautions against static discharge.

    The input can be a pulse rate for motor speed, allowing a servo loop to
be performed utilizing the PWM output.
 

6.0 AXIS ENCODER & LIMITS INPUTS

    Each motor axis has an associated encoder and limits input. The
encoder input may be used to verify step position. The two flag may be used
for home positions. Power of plus five volts is also available on the
connector for powering the encoder and flags interface.

    The input signals expected are 0 to +5v with TTL input thresholds of 1.5
volts. These are not opto-isolated inputs, so care must be taken for noise
suppression, and precautions against static discharge. The encoder phase
inputs have extensive digital filtering, but it is still suggested that the
cable run from the system be shielded, with the shield connected to the
ground connection on the interface connector.

    The system hardware and firmware implements a 32 bit axis position
counter which may be initialized, and read over the serial control
interface.

    The LIMIT flag is accessed by a built in system homing routine. The
meaning of its polarity can be set over the serial control interface.

    These 4 input pins may also be used, via reprogramming the hardware, as
general purpose input or output points.
 
 

7.0 TRAINING ENCODERS

    There are two sets of encoder phase inputs, which may be hooked to
encoders on joysticks, hand wheels, etc. for use as training inputs. For
custom applications they may be reprogrammed as general purpose I/O. Power
of plus five volts is also available on the connector for powering the
training interface.

    The input signals expected are 0 to +5v with TTL input thresholds of 1.5
volts. These are not opto-isolated inputs, so care must be taken for noise
suppression, and precautions against static discharge. The encoder phase
inputs have extensive digital filtering, but it is still suggested that the
cable run from the system be shielded, with the shield connected to the
ground connection on the interface connector.

    The system hardware and firmware implements two 32 bit training axis
position counters which may be initialized, and read over the serial control
interface.

    These two training inputs can be linked via a software switch, to control
two axes of the system directly through a motor/training ratio. (See software
section) The two flag inputs may be used as indexes for the training
encoders.

    These 6 input pins may also be used, via reprogramming the hardware, as
general purpose input or output points.
 
 

8.0 STEPPING MOTOR DRIVE

    There are four bi-polar H-bridge motor drives in the SS4544 system.
Each motor drive has it own connector, with two connections for the motor's
Phase-A winding, and two for Phase-B, and a fifth connection for ground
shielding.

    The drivers can be set up to a maximum of 5 amps, with +-44 volt chopper
drive running at 50 khz. The full step speed can range from 1 to 50,000
steps per second. The system can be used to position to as fine as 1/512th
of a step.

    The motor drive current is updated synchronously at the 50 khz rate,
with the current being adjusted in 1/64ths of a step. This means that at
slow speeds (<781 sps), micro-stepping occurs in 1/64ths of a step, and as
the speed gets faster, the micro-step size gets larger.

    All motors are updated synchronously, as well as the switching power
converter, thus allowing for digital filtering, and elimination of cross
conduction of noise between axes, and the power converter. The result is
very quiet, smooth control of the stepping motors.
 
 
 

8.1 AXIS DRIVE SPECIFICATION SUMMARY

    TYPE                         - DMOS Recirculating H-Bridge
    VOLTAGE                 - 44 Volts
    CURRENT                 - 5 Amp Maximum
    PROTECTION           - Electronic Fusing @ ~8 Amp
    MICROSTEPPING     - Default SINE/COS - User Programmable & Auto-tuning
    RANGES                    - 4 Ranges for Holding, Acceleration, Running, and Manual
    CHOP FREQUENCY - 50 Khz
    MOTOR RANGE       - 1-5 Amp 1-10 Millihenry
    STEP RATE               - 1-50,000 s/sec
    POSITIONING           - 32 bits (22.10 4,194,240 steps, 1024 micro-steps)
    RESOLUTION           - 1/64th Step (Optional 1/256)
    FEEDBACK               - Optional Encoder (32 bit)
    INDICATOR              - LED (Axis Enabled)
    COMMUTATION      - Automatic current sense offset adjustment
 

8.2 CONNECTING MOTORS

    The SS4544 systems have bi-polar output drive, meaning that current is
driven both positive and negative through the motor windings. Typical motors
come with 4 leads, 6 leads, or 8 leads. The 4 leaded motor is designed for
bi-polar drive, and obviously there are no connection choices. For optimum
performance with a standard SS4544 system, the motor inductance seen by the
driver should be in the 1 to 10 Millihenry range, and drive currents
requirements in the 2 to 5 amp range. The motor direction may be reversed
by swapping leads on either the A or B phase outputs of the driver, or by
changing the axis direction flag through software.

MOTORS WITH 3 LEADS PER PHASE (6 lead motor)

    These were designed for uni-polar drive. With a uni-polar driver, the
center tap of a phase winding is connected usually to positive supply
voltage, and the ends of the winding are alternatively switched to ground by
the drivers. You have three choices for connection to the SS4544 system.
Two of these choices are really the same choice, leaving the following:

    i. Drive through the windings at 1/2 rated motor current, leaving the
       center tap unconnected.

      Advantages  - similar torque at half the current.
                         - lower driver I squared R losses

    Disadvantage - lower top speed due to 2x back EMF voltage.
                         - higher inductance

    ii. Drive through half the winding at full rated motor current,
       connecting to the center tap and one of the ends, leaving the other
       end unconnected.

    Advantages   - Higher motor performance
                         - lower inductance

MOTORS WITH 4 LEADS PER PHASE (8 lead motor)

    These were designed for either type drive. Connecting is a little more
difficult, because you will have to identify which windings are paired
(belong to the same phase), and the polarity of the pair if you are going to
series, or parallel them. If you series the phase pair you have case i.
above. If you just drive one winding from each pair you have case ii.
above. You have the third possibility:

    iii. Drive through both phase pair of windings connected in parallel. If
        you don't phase these correctly, of course it's not going to work.

    Advantages -  Highest motor performance
                       - Lowest inductance
                       - Highest efficiency
 

9.0 INDICATORS

    There are nine indicators on the system, power, brake, electronic axis
fuses, RS-485, RS-232 Transmit, and RS-232 Receive.

Power - This green LED is lit whenever system power is running. It is
             located next to the input power plug.

Brake -  This red LED is lit whenever power is being absorbed by the
             system due to dynamic braking, i.e. the motors are acting as
             generators during deceleration. I also may be lit when all
             motors are turned off.

Axis  -   These green LEDs are lit whenever a corresponding axis is enabled
             and power is being applied to an axis motor. If a fault
             condition occurs, the light will go out. Electronic sensing
             protects against any kinds of shorts in the motor circuitry.

RS485 - This green LED will be modulated during bus transmission.

RS232 - The red LED will be modulated during system transmission.
              The green LED will be modulated during system reception.
 

A.0 USER +5V POWER

    The +5V power available to the user on, limits, training, and
RS-485-OUT connectors is a separate supply limited to an aggregate current
of 1.0 amp. Shorting out this supply will not damage the unit, nor stop its
operation other than killing communications to any user devices powered by
this supply (encoders, etc.).

    The output at the connectors should be 5v +-2%. The voltage drop due to
cable resistance needs to be taken into account to insure operation of the
user circuits.