DMC-21x3 Accessories Chapter 9 AMP-20540/20520• 55
Figure 27 Peak Current Operation (DMC-2143 and AMP-20540)
With the AMP-20540 and 20520, the user is also given the ability to choose between normal
and high current bandwidth (AU). In addition, the user can calculate what the bandwidth of the
current loop is for their specific combination (AW). To select normal current loop gain for the
X axis and high current loop gain for the Y axis, issue AU 0,1. The command AW is used to
calculate the bandwidth of the amplifier using the basic amplifier parameters. To calculate the
bandwidth for the X axis, issue AWX=v,l,n where v represents the DC voltage input to the card,
l represents the inductance of the motor in millihenries, and n represents 0 or 1 for the AU
setting.
Note: For most applications, unless the motor has more than 5 mH of inductance with a 24V
supply, or 10 mH of inductance with a 48 volts supply, the normal current loop bandwidth
option should be chosen. AW will return the current loop bandwidth in Hertz.
Brush Amplifier Operation
The AMP-20540 and AMP-20520 also allow for brush operation. To configure an axis for
brush-type operation, connect the 2 motor leads to Phase A and Phase B connections for the
axis. Connect the encoders, homes, and limits as required. Set the controller into brush-axis
operation by issuing BR n,n,n,n. By setting n=1, the controller will operate in brushed mode on
that axis. For example, BR0,1,0,0 sets the Y-axis as brush-type, all others as brushless. If an
axis is set to brush-type, the amplifier has no need for the Hall inputs. These inputs can
subsequently be used as general-use inputs, queried with the QH command. The gain settings
for the amplifier are identical for the brush and brushless operation. The gain settings can be set
to 0.4, 0.7, or 1.0 A/V, represented by gain values of 0, 1, and 2 (e.g.. AG 0,0,2,1). The current
loop gain AU can also be set to either 0 for normal, or 1 for high current loop gain.
Using External Amplifiers
The AMP-205x0 breaks out the step/direction or amplifier enable/motor command signals to
control an external servo or stepper amplifier. For example, a machine might have two axes that
use the AMP-20520 and two stepper axes that use external drivers. The pulse and direction
signals are accessed through the high density 44-pin D-sub connector. The same connector pins
are used to bring out the amplifier enable and motor command line. Which signals are brought
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