RM42A Digital Stepper Drive User Manual
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7.2 Output Current Configurations
For a given motor, higher drive current will make the motor to output more torque, but at the same time causes more
heating in the motor and drive. Therefore, output current is generally set to be such that the motor will not overheat for
long time operation. Since parallel and serial connections of motor coils will significantly change resulting inductance
and resistance, it is therefore important to set drive output current depending on motor phase current, motor leads and
connection methods. Phase current rating supplied by motor manufacturer is important in selecting drive current,
however the selection also depends on leads and connections.
The first three bits (SW1, 2, 3) of the DIP switch are used to set the dynamic current. Select a setting closest to your
motor’s required current.
Note: “default” means the parameters can be set by software.
7.2.1 Dynamic Current Configurations
Peak Current
RMS Current
SW1
SW2
SW3
1.00A
0.71A (default)
ON
ON
ON
1.46A
1.04A
OFF
ON
ON
1.91A
1.36A
ON
OFF
ON
2.37A
1.69A
OFF
OFF
ON
2.84A
2.03A
ON
ON
OFF
3.31A
2.36A
OFF
ON
OFF
3.76A
2.69A
ON
OFF
OFF
4.20A
3.00A
OFF
OFF
OFF
7.2.2 Idle Current Configuration
SW4 is used to set motor idle current percentage. At OFF position it means the standstill current is set to be 50% of the
selected output current. At ON position it means standstill current is set to be 90%.
The current automatically reduced to 50% of the selected dynamic current 0.4 second after the last pulse.
7.3 Automatic Motor Matching & Self Configuration
When powered on a RM42A will automatically configure itself with the best settings to match the driven stepper motor
for optimal performance. No action is needed.
8. Wiring Notes
l
In order to improve anti-interference performance of the drive, it is recommended to use twisted pair shield cable.
l
To prevent noise incurred in PUL/DIR signal, pulse/direction signal wires and motor wires should not be tied up
together. It is better to separate them by at least 10 cm, otherwise the disturbing signals generated by motor will
easily disturb pulse direction signals, causing motor position error, system instability and other failures.
l
If only one power supply serves multiple RM42A drives, separately connecting the drives to the power supply is
recommended instead of daisy-chaining.
l
It is prohibited to pull and plug connector P2 while the drive is powered ON, because there is high current flowing
through motor coils (even when motor is at standstill). Pulling or plugging connector P2 with power on will cause
extremely high back-EMF voltage surge, which may damage the drive.
