FIRST Global Building Guide Created by REV Robotics 2019, Licensed Under CC BY-SA
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The female hex shaft of the Core Hex Motor allows for any length 5mm hex shaft to be inserted through the body of the
motor (Figure 8). The motor can drive wheels or gears on either side of the shaft, or a single shaft can be put through
multiple motors to increase the power. If multiple motors are used on a single shaft, be sure that they are being controlled
in the same direction to prevent damage.
Figure 8: Hex Core Motor Mounted with 5mm Shaft Inserted
2.4
SERVO MOTORS
Servo motors are a specialized kind of motor which can be controlled to move to a specific angle instead of continuously
rotating like a DC motor. Instead of a hex output shaft like the DC motor, servos have an output spline (Figure 9). A spline
is a specific groove pattern cut into the shaft which allows the rotation of the servo motor to be transmitted to the
attached Aluminum Servo Horn or Servo Adapter (see Table 6). Splines are like keys, so only matched types will fit
together. The REV Robotics Servos all use a 25T spline pattern. If the gears or spline of the REV Robotics Smart Robot
Servo become damaged, they are replaceable using a Replacement Gear Set. See the Replacement Gear Guide for
instructions.
Figure 9: Servo Motor
Common servo motors take a programmed input signal range and map that to an angular range. For example, for a servo
with a 180° range, if the input range was from 0 to 1 then a signal input of 0 would cause the servo to turn to point -90°.
For a signal input of 1, the servo would turn to +90° (Figure 10). Inputs between the minimum and maximum have
corresponding angles evenly distributed between the minimum and maximum servo angle.
Figure 10: Servo Motor Angular Mode Output
