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Regulated or Unregulated Power Supply
Both regulated and unregulated power supplies can be used to supply the driver. However,
unregulated power supplies are preferred due to their ability to withstand current surge. If regulated
power supplies (such as most switching supplies.) are indeed used, it is important to have large
current output rating to avoid problems like current clamp, for example using 4A supply for 3A
motor-driver operation. On the other hand, if unregulated supply is used, one may use a power supply
of lower current rating than that of motor (typically 50%～70% of motor current). The reason is that
the driver draws current from the power supply capacitor of the unregulated supply only during the
ON duration of the PWM cycle, but not during the OFF duration. Therefore, the average current
withdrawn from power supply is considerably less than motor current. For example, two 3A motors
can be well supplied by one power supply of 4A rating.
Multiple Drivers
It is recommended to have multiple drivers 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 drivers. (Instead, please connect them to power supply separately.)
Attention:
NEVER connect power and ground in the wrong direction, as it will damage the M325.
Selecting Supply Voltage
The power MOSFETS inside the M325 can actually operate within +12V～+24VDC, 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 driver 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 +12～+ 20V, leaving room for power fluctuation and
back-EMF.
7. Selecting Microstep Resolution and Driver Output Current
This driver uses a 6-bit DIP switch to set microstep resolution, and motor operating current, as shown
below:
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M325 Micro Microstepping Driver Manual V2.0
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Microstep Resolution Selection
Microstep resolution is set by SW 5, SW 6 of the DIP switch as shown in the following table:
Microstep
Steps/rev.(for 1.8°motor)
1
200
2
400
4
800
8
1600
Current Settings
For a given motor, higher driver current will make the motor to output more torque, but at the same
time causes more heating in the motor and driver. 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 driver output current depending on motor phase current, motor leads and connection methods.
Phase current rating supplied by motor manufacturer is important in selecting driver 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.
Dynamic Current Setting
Peak current (A)
SW1
0.39A
OFF
0.71A
ON
1.10A
OFF
1.42A
ON
1.81A
OFF
2.13A
ON
2.52A
OFF
Notes:
Due to motor inductance, the actual current in the coil may be smaller than the dynamic
current setting, particularly under high speed condition.
Standstill Current
SW4 is used for this purpose. OFF meaning that the standstill current is set to be half of the selected
dynamic current, and ON meaning that standstill current is set to be the same as the selected dynamic
current.
The current automatically reduced to 60% of the selected dynamic current 0.2 second after the last
pulse. Theoretically, this will reduce motor heating to 36% (due to P=I
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M325 Micro Microstepping Driver Manual V2.0
SW5
SW6
ON
ON
OFF
ON
ON
OFF
OFF
OFF
SW2
SW3
ON
ON
OFF
ON
OFF
ON
ON
OFF
ON
OFF
OFF
OFF
OFF
OFF
2
*R) of the original value. If
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