User Manual

MCP Series
Brushed DC Motor Controllers
MCP Series User Manual
11
1.0 Introduction
1.0.1 Motor Selection
When selecting a motor controller several factors should be considered. All DC brushed motors
will have two current ratings, maximum stall current and continuous current. The most important
rating is the stall current. Choose a model that can support the stall current of the motor
selected to insure the motor can be driven properly without damage to the motor controller.
1.0.2 Stall Current
A motor at rest is in a stalled condition. This means during start up the motors stall current can
be reached. The loading of the motor will determine how long maximum stall current is required.
A motor that is required to start and stop or change directions rapidly even with a light load may
still require maximum stall current often.
1.0.3 Running Current
The continuous current rating of a motor is the maximum current the motor can run without
overheating and eventually failing. The continuous current rating on most motors is several
times lower than the stall current rating of the motor. The continuous running current of the
motor should not exceed the continuous current rating of the motor to prevent damage to the
motor.
1.0.4 Wire Lengths
Wire lengths to the motors and from the battery should be kept as short as possible. Longer
wires will create increased inductance which will produce undesirable effects such as electrical
noise or increased current and voltage ripple in the DC Link capacitors. The power supply/battery
wires must be as short as possible. They should also be sized appropriately for the amount of
current being drawn. Increased inductance in the power source wires will increase the ripple
current/voltage which can damage the DC Link capacitors on the board and/or causing voltage
spikes over the rated voltage of the motor controller, leading to controller failure.
1.0.5 Run Away
During development of your project caution should be taken to avoid run away conditions.
The motors should be mounted securely and allowed to rotate freely until properly setup. If
the motor is embedded, ensure you have a safe and easy method to remove power from the
controller as a fail safe.
1.0.6 Disconnect
To assure powering off in an emergency, a properly sized switch and/or contactor should be
used. Also because the power may be disconnected at any time there should be a path for
regeneration energy back to the battery even after the power has been disconnected. Use a
power diode with proper ratings to provide a path across the switch/contactor and any fuse.
1.0.7 Encoders
MCP features dual quadrature encoders along with various other encoder options such as
absolute. When wiring encoders make sure the direction of spin is the correct direction relative
to the motor direction. Incorrect encoder connections can cause a run away state. Refer to the
encoder section of this user manual for proper setup. In addition some encoders can cause
excessive noise on the +5VDC rail of the controller. This excessive noise will cause unpredictable
behavior in velocity and position control modes.