
M542 Microstepping Driver Manual V1.0
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Figure 9: 8-lead motor parallel connections
6. Power Supply Selection
The M542 can match Large and small size stepping motors (from Nema size 17 to 34) made by us 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average current withdrawn from power supply is considerably less than motor current.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.
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 M542 can actually operate within +20 ~ +100VDC, 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 +24 ~ +50VDC,
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: