Students will describe how a hobby servo differs from a continuous rotation motor
Students will identify the three servo wires by color and function
Students will correctly connect a servo to the Micro:bit breakout board
Materials:
1 Micro:bit with USB cable per student
1 breakout board per student
1 hobby servo (SG90 or similar) per student
Battery pack with USB cable (optional, for higher torque)
Timing:
0-5 min: Introduce hobby servos; show physical servo and discuss how it differs from a brushed motor
5-10 min: Explain servo internals (motor, gear train, position sensor, control circuit)
10-15 min: Demonstrate the three-wire connection; emphasize wire color orientation
15-20 min: Students connect their servos to Pin 0
20-25 min: Instructor checks each connection before powering on
Key Concepts:
A hobby servo contains a brushed motor, gear train, position sensor, and control circuitry
Servos move to a specific angle (0-180 degrees) rather than spinning continuously
The three wires are: brown (ground), red (power), and orange (signal)
Servos are common in hobby robotics but too inaccurate for most commercial products
Common Mistakes:
Plugging the servo connector in backward (brown wire on signal instead of ground)
Connecting to the wrong pin group on the breakout board
Trying to manually force the servo horn past its 180-degree range (can strip gears)
Expecting continuous rotation from a standard hobby servo
Assessment Cues:
Student can name the three wires and their functions without looking at notes
Student’s servo connector is oriented correctly on the breakout board
Student can explain why a servo is useful for a robot arm but not for wheels
Differentiation:
Struggling: Provide a color-coded reference card showing which wire goes where; mark Pin 0 on the breakout board with tape
Advanced: Have student research continuous rotation servos and explain how they differ from standard servos
What Is a Hobby Servo?
A hobby servo is built from a regular brushed motor, a gear train, a position
sensor, and some internal circuitry. It will only move back and forth 180
degrees – it cannot turn around continuously. This makes servos useful for
moving joints on a robot arm or flaps on an airplane, but not for wheels on a
car.
Hobby servos are very inexpensive and easy to use, so they are common in hobby
projects. While there are some industrial versions, their inaccuracy makes them
rare in commercial products.
Servo Wire Colors
Every hobby servo has three wires:
Wire Color
Function
Breakout Pin
Brown
Ground
Black (-)
Red
Power
Red (+)
Orange
Signal
Yellow
Connections
Servo connections are simple: just plug the three-position connector on the end
of the servo directly onto the three pins for Pin 0 on the breakout board.
Make sure that:
The brown servo wire connects to ground (black pin)
The orange servo wire connects to signal (yellow pin)
Tip
The connector can only go on one way if you match the colors. If you are unsure,
ask your instructor to check before powering on.
Warning
Do not try to manually turn the servo horn past its limits. The gears inside are
small plastic teeth and can be stripped if forced.
