6. Power Supply Selection
The MC860H can match medium and small size stepping motors (from NEMA frame size
17 to 34) made by Lichuan 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withdrawn from power supply is considerably less than motor current.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 MC860H can actually operate within +24 ~ +90VDC or
18~80VAC, 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 ~ +50VDC or 18~80VAC, leaving room for power
fluctuation and back-EMF.
7. Selecting Microstep Resolution and 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:
