Vansco VMM3120, User Manual

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58 VMM3120
Application Examples
9.4. Controlling Motor Speed
The VMM3120 can be used to control the DC motor speed of motors that provide
a tachometer output.
Note: The VMM3120 has Proportional Integral Differential (PID) capabilities
that make it possible to control devices like proportional valves through
software. Refer to the appropriate software manual, or contact your Parker
Vansco Account Representative for more details about software. This section
only provides hardware connection information.
To do this, you would use a high-side output with PWM capabilities to control the
speed of the motor, and a DC-coupled frequency input to monitor the output from
the motor.
The application code should be written so that the PWM duty cycle for the high-
side output is adjusted to achieve a target speed (frequency) for the motor.

If the frequency feedback is lower than target, the PWM duty cycle should
increase to boost the average current through the motor to speed it up.

If the frequency feedback is higher than target, the PWM duty cycle should
decrease to reduce average current through the motor to slow it down.
The following shows how to connect the VMM3120 to control the speed of a
motor:
Internal to product
Motor
Frequency Input
High-Side Output
(PWM)
Battery Voltage
Figure 27: Connection for controlling motor speed