PSR8078 User Manual
REV1.0 7
5.3.2 Parallel Connections
An 8-lead motor in a parallel configuration offers a more stable, but lower torque at lower
speed. But because of the lower inductance, there will be higher torque at higher speed.
Multiply per phase (or unipolar) current rating by 1.96, or the bipolar current rating by 1.4, to
determine the peak output current.
Figure 8: 8-lead motor parallel connections
6. Power Supply Selection
The stepper drive PSR8078 can match medium and large stepping motors (from NEMA size
34 to 42). To achieve good driving performances, it is important to select supply voltage and
output current properly. Generally speaking, supply voltage determines the high speed
performance of the motor, while output current determines the output torque of the driven
motor (particularly at lower speed). Higher supply voltage will allow higher motor speed to be
achieved, at the price of more noise and heating. If the motion speed requirement is low, it’s
better to use lower supply voltage to decrease noise, heating and improve reliability.
6.1 Multiple Drives
It is recommended to have multiple drives to share one power supply to reduce cost, if the
supply has enough capacity. To avoid cross interference,
DO NOT
daisy-chain the power
supply input pins of the drives. (Instead, please connect them to power supply separately.)
6.2 Selecting Supply Voltage
The power MOSFETS inside the stepper drive PSR8078 can actually operate 24V
～
+80VDC, including power input fluctuation and back EMF voltage generated by motor coils
during motor shaft deceleration. Higher supply voltage can increase motor torque at higher
speeds, thus helpful for avoiding losing steps. However, higher voltage may cause bigger
motor vibration at lower speed, and it may also cause over-voltage protection or even drive
damage. Therefore, it is suggested to choose only sufficiently high supply voltage for
intended applications, and it is suggested to use power supplies with theoretical output
voltage of +24
～
+ 72V, leaving room for power fluctuation and back-EMF.
PSR8078 User Manual
REV1.0 8
7. Selecting Microstep Resolution and Drive Output Current
This drive uses an 8-bit DIP switch to set microstep resolution, and motor operating current,
as shown below:
7.1 Microstep Resolution Selection
Microstep resolution is set by SW5, 6, 7, 8 of the DIP switch
as shown in the following table:
Microstep
Steps/Rev.
(for 1.8°motor)
SW5
SW6
SW7
SW8
2
400
ON
ON
ON
ON
4
800
OFF
ON
ON
ON
8
1,600
ON
OFF
ON
ON
16
3,200
OFF
OFF
ON
ON
32
6,400
ON
ON
OFF
ON
64
12,800
OFF
ON
OFF
ON
128
25,600
ON
OFF
OFF
ON
256
51,200
OFF
OFF
OFF
ON
5
1,000
ON
ON
ON
OFF
10
2,000
OFF
ON
ON
OFF
25
5,000
ON
OFF
ON
OFF
50
10,000
OFF
OFF
ON
OFF
125
25,000
ON
ON
OFF
OFF
250
50,000
OFF
ON
OFF
OFF
7.2 Current Settings
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
