P
M752 Microstepping Driver Manual V1.0
Tel: +44 (0)1202 237770 7
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 9: 8-lead motor parallel connections
6. Power Supply Selection
The P M752 can match medium and small size stepping motors (from NEMA frame size 17 to 43)
Supplied
by
Zapp Automation Ltd
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withdrawn from power supply is considerably less than motor current.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.
PM752 Microstepping Driver Manual V1.0
Tel: +44 (0)1202 237770 8
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 PM752 can actually operate 20 ~ +75VDC, 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 ~ +68VDC, leaving room for power fluctuation and back-EMF.
7. Selecting Microstep Resolution and Driver Output Current
This driver uses an 8-bit DIP switch to set microstep resolution, and motor operating current, as
shown below:
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
1600
OFF
OFF
ON
ON
16
3200
ON
OFF
ON
ON
32
6400
ON
ON
OFF
ON
64
12800
OFF
ON
OFF
ON
128
25600
OFF
OFF
OFF
ON
256
51200
ON
OFF
OFF
ON
5
1000
ON
ON
ON
OFF
10
2000
OFF
ON
ON
OFF
