Anaheim MICROSTEP DRIVER MDM40001 - Manual (Page 6)

#L010068 #L010068 9 10
DETERMINING OUTPUT CURRENT Reducing the output current in the MDM40001 can be accomplished by connecting an
The output current for the motor used when microstepping is determined differently from automatically 1 second after the last positive going edge of the step clock input. See
that of a half/full unipolar driver. In the MDM40001, a sine/cosine output function is Figure 1 for TYPICAL HOOK-UP.
used in rotating the motor. The output current for a given motor is determined by the
motors current rating and the configuration for how the motor is hooked up. There is a
The amount of current per Phase in the reduction mode is related to the value of the
current adjustment resistor used to set the output current of the MDM40001. This sets current adjustment resistor and the current reduction resistor. When the current
the peak output current of the sine/cosine waves. The specified motor current (which is reduction circuit is activated, the current reduction resistor is paralleled with the current
the RMS value) is multiplied by a factor of 0.7, 1.0, or 1.4 depending on the motor adjustment resistor. This lowers the total resistance value, and thus lowers the per Phase
configuration (half-coil, series, or parallel). output current. The relationship between the output current and the resistor's value is as
SETTING OUTPUT CURRENT
The output current on the MDM40001 is set by an external ±1%, 1/8 watt (or higher)
resistor between pins 2 and 3 of connector P2. This resistor determines the per Phase
RMS output current of the driver. The MDM40001 uses a 1mA current source to
establish the reference voltage needed to control the output current. The relationship
between the output current and the resistor value is as follows:
RMS OUTPUT CURRENT (Amps) = (0.707)(0.002)(Resistance in Ohms) See
Figure1
RMS Current Resistor Value RMS Current Resistor Value
0.3 A 210 1.2 845
0.4 280 1.4 976
0.5 357 1.6 1130
0.6 422 1.8 1270
0.7 487 2.0 1400
0.8 562 2.2 1540
0.9 634 2.4 1690
1.0 698 2.6 1820
1.1 768 2.82 2000
TABLE 3: RESISTOR VALUES WITH RESPECT TO OUTPUT CURRENT
Closest 1% value selected
WARNING! A current adjustment resistor is always necessary to keep the drive in a safe
operating region. Do not operate the driver without a current adjustment resistor. When connecting
the CURRENT ADJUSTMENT resistor between Pins 3 and 2 of Connector P2 the length of the
leads should be as short as possible to help minimize the noise coupled into the driver . Refer to
Figure 1 for TYPICAL HOOK-UP.
REDUCING OUTPUT CURRENT
Output Reduction Current (Amps)= .002 x *R(Current Adjust) xR(CurrentReduction)
R(Current Adjust) +R(CurrentReduction)
external resistor (1/8 watt or higher) between pins 1and 2 of connector P2 and ocurrs
follows:
NOTE: When connecting the current reduction resistor between pins 1 and 2 of
connector
P2 , the lenth of the leads should be as short as possible to help minimize noise coupled
into the driver.
MOTOR SELECTION
The MDM40001 is a Bipolar driver working equally well with both Bipolar and Unipolar
Motor Configurations,( i.e. 8 and 4 lead motors and 6 lead center tapped motors).
Motors with low current ratings and high inductance will perform better at low speeds,
providing higher low-end torque. Motors with high current ratings and low inductance
will perform better at higher speeds, providing higher high-end torque.
Since the MDM40001 is a constant current source, it is not necessary to use a motor that
is rated at the same voltage as the supply voltage. What is important is that the
MDM40001 is set to the appropriate current level based on the motor being used.
Higher voltages will cause the current to flow faster through the motor coils. This in turn
means higher step rates can be achieved. Care should be taken not to exceed the
maximum voltage of the driver.