DM856 Digital Stepping Driver Manual V1.0
Tel: +086 0755-26434369 7 Web Site: www.leadshine.com
Parallel Connections
An 8 lead motor in a parallel configuration offers a more stable, but lower torque at lower speeds. But
because of the lower inductance, there will be higher torque at higher speeds. Multiply the 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
NEVER
disconnect or connect the motor while the power source is energized.
6. Power Supply Selection
The DM856 can match medium and small size stepping motors (from NEMA frame size 17 to 34)
made by Leadshine or other motor manufactures around the world. 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.
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withdrawn from power supply is considerably less than motor current.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.
DM856 Digital Stepping Driver Manual V1.0
Tel: +086 0755-26434369 8 Web Site: www.leadshine.com
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.
Selecting Supply Voltage
The power MOSFETS inside the DM856 can actually operate within +20 ~ +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 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 +20 ~ +72VDC, leaving room for power fluctuation and
back-EMF.
7. Selecting Microstep Resolution and Driver Output Current
Microstep resolutions and output current are programmable, the former can be set from full-step to
102,400 steps/rev and the latter can be set from 0.5A to 5.6A. See more information about
Microstep
and Output Current Setting
in Section 13.
However, when it
’
s not in software configured mode, this driver uses an 8-bit DIP switch to set
microstep resolution, and motor operating current, as shown below:
Microstep Resolution Selection
When it
’
s not in software configured mode, microstep resolution is set by SW5, 6, 7, 8 of the DIP
switch
as shown in the following table:
