10
November 2006
Reducing Output Current
Reducing the output current is accomplished by setting switch 3 of SW1 to the on position and occurs
approximately 1 second after the last step clock input. The amount of current per phase in the reduction
mode is approximately 70% of the set current. When the current reduction circuit is activated, the current
reduction resistor is paralleled with the current adjustment potentiometer. This lowers the total resistance
value, and thus lowers the per phase output current.
Step Motor Configurations
Step motors can be configured as 4, 6, or 8 leads. Each configuration requires different currents. Refer
to the lead configurations and the procedures to determine their output current.
WARNING!
Step motors will run hot even when configured correctly. Damage may occur to the motor if
a higher than specified current is used. Most specified motor currents are maximum values. Care should
be taken to not exceed these ratings.
Determining Output Current
The output current used for the motor when microstepping is determined differently from that of a full/half
step unipolar driver. In the MBC25PG1(L), a sine/cosine output function is used in rotating the motor. The
output current for a given motor is determined by the motors current rating and the wiring configuration of
the motor. There is a current adjustment potentiometer used to set the output current of the MBC25PG1(L).
This sets the peak output current of the sine/cosine waves. The specified motor current (which is the
unipolar value) is multiplied by a factor of 1.0, 1.4, or 2.0 depending on the motor configuration (series,
half-coil, or parallel).
6 Lead Motors
When configuring a 6 lead motor in a
half-coil configuration
(connected from one end of the coil to the
center tap), multiply the specified per phase (or unipolar) current rating by 1.4 to determine the current
setting potentiometer value. This configuration will provide more torque at higher speeds when compared
to the series configuration.
When configuring the motor in a
series configuration
(connected from end to end with the center tap
floating) use the specified per phase (or unipolar) current rating to determine the current setting potenti
-
ometer value.
July 2018
July 2018
