MMP SA-2550A
Page 9 of 24
Midwest Motion Products
DESIGN, MANUFACTURING & DISTRIBUTION - MOTION CONTROL EQUIPMENT
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Using an Encoder Feedback with a Servo Amplifier
Encoders can be used with the MMP SA-2550A to provide feedback to the amplifier and control speed of the motor. The default
setting on the servo amplifier is duty cycle mode. This mode does not use motor feedback. If motor speed as feedback is required
then using an encoder as feedback to the Servo Amplifier is recommended. For encoder feedback the MMP SA-2550A needs to be
properly configured and wired.
The resolution of the encoder and speed of the motor is important for proper speed control. The MMP SA-2550A uses both
parameters to input a switching frequency and thus control the motor speed. The MMP SA-2550A has a maximum switching
frequency of 24 kHz (Specifications table, page 4). As long as the input frequency is no less than 10 Hz and does not exceed the
maximum frequency the servo amplifier is able to control speed smoothly. Typically an encoder resolution is chosen that maximizes
the input frequency without exceeding the switching frequency. The encoder resolution is also chosen based on the following
guidelines for expected maximum motor speed:
Maximum Motor Speed (RPM) Encoder Resolution (Counts per Revolution)
Greater Than
Less Than
Greater Than
Less Than
2500
500
2500
5000
250
500
5000
10000
100
250
10000
100
To utilize encoder feedback ensure the SW1 switches are configured as specified on page #.
As shown below, ensure the encoder, potentiometer and external encoder source are grounded. Note that the encoder must be
powered by an external source (usually 5 VDC). If the encoder channels are double ended then use the positive signal of each
channel (labeled A+ and B+ on the below figure) as the feedback signal to the servo amplifier.
Figure 1. Encoder feedback wiring with potentiometer command.
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