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25
Speed Controller
Speed controllers are extremely important in regulating the speed and direction
of the motors being used. For this design, the IFI VEX Pro Victor 884 model will be
used. This model, as shown in Figure 23 below, will be controlled by the modified signal
coming from the R-4 receiver. Speed controllers regulate the motors by varying the
amount of voltage that is input to each motor. After the transmitted signal is processed
by the receiver and output to the speed controller, the H-bridge circuit of the controller
determines which way the current is flowing through and thus which direction the motor
should turn. The amount of voltage input into the controller determines the speed of the
motor.
To operate a differential motor, as will be used in this design, two speed
controllers will be used. Each controller will be independent of the other and will be
controlled by the embedded code of the receiver. As the signal is received from the
transmitter, it will be distributed between the two controllers, depending upon the
positioning of the joystick on the remote. The signal sent from the controller will
determine how fast each motor must turn in order to maintain straight movement, as
well as how much more power one motor must receive in order to execute a turn.
This particular controller is specifically designed for robotic applications and
therefore matches many of the specifications desired for this project. It is able to
withstand currents up to 40A and has a low voltage drop and ideal peak surge capacity.
It operates on voltages between 6V and 15V and is also extremely light, weighing in at
4oz. per unit. Excerpts from the user manual can be found in the Appendix of this
report.
Figure 23: VEX Pro Victor 884 Speed Controller.
Motor
The motor that will be used for the device is the NPC-41250. Depicted in Figure
24, this motor is a 12 V DC motor capable of providing a maximum of 260 in/lbs of
torque at a rate of 93 RPM. This motor also only requires approximately 6.78 A of