Continuous Servo Movement Panel

Continuous rotation servos are a popular way to power small robots. You attach a wheel (or tread sprocket) directly to each servo horn and use them like drive motors.

Unlike a standard positional servo (which moves to a specific angle like 0°–180°), a continuous rotation servo spins continuously like a motor. You don’t tell it “go to 120°”—instead you tell it “spin forward”, “spin backward”, or “stop”.

A continuous servo is usually a modified standard servo. Two internal parts are changed so it can rotate 360° forever:

1. Mechanical Stop Removed
   A standard servo has a built-in physical stop on the internal gear so it cannot rotate past about 180°. Continuous servos remove that stop so the output shaft can keep turning.
2. Potentiometer Disabled/Removed
   A standard servo uses a potentiometer (a position sensor) to know its current angle. That sensor can only turn a limited amount. When it’s removed or replaced with fixed resistors, the servo no longer knows its position—so it can’t “hold” an angle anymore. Instead, the input signal becomes a speed/direction command.

1) Movement Panel

Use these buttons to drive your robot:

• Forward: both servos spin to move the robot forward
• Reverse: both servos spin to move the robot backward
• Left/Right: one side spins faster or opposite to turn the robot
• Stop: stops movement (behavior depends on a setting explained below)

2) Speed Sliders

These sliders set the speed for each servo (0–100%). The default is 0%, which means the servo is OFF until you raise the slider.

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Why two sliders? Many robots drift left or right because one servo spins slightly faster than the other. You can “trim” the speeds by lowering the faster side.

Note: Not all continuous servos support true variable speed. Some will behave more like “on/off” around certain values, depending on the servo brand and type.

1) Title Field

The name of this skill as it appears in your ARC project. Rename it if you have multiple movement skills and want to stay organized.

2) Left Servo Port Drop-down

Choose the digital port on the EZ-B where the left continuous servo signal wire is connected (example: D0).

3) Left Servo Forward / Reverse / Stop Value Drop-downs

Continuous servos still receive “servo position” style signals (1–180), but those values act like speed/direction.

• Stop is usually around 90
• Values above 90 typically spin one direction
• Values below 90 typically spin the other direction

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The default example behavior for the left servo is:

• Forward: 180
• Reverse: 1
• Stop: 90

If your servo stops slowly, creeps when “stopped”, or the direction feels backwards, you can adjust these values.

4) Test Buttons (Left)

Quickly tests the Left servo using your selected Forward/Reverse/Stop values without switching back to the main window. This is helpful for confirming wiring and direction.

5) Use Checkbox (Stop Behavior)

This setting changes what happens when you press Stop:

• Unchecked (default): ARC stops sending the PWM signal when you press Stop. The servo will “coast” or stop naturally. This can reduce drifting on some analog continuous servos.
• Checked: ARC keeps sending the PWM signal and uses your Stop value (usually 90). This can feel more like a “brake” because the servo actively holds the stop command.

Beginner tip: If your robot slowly creeps forward or backward when you press Stop, try leaving this unchecked (default). If your robot rolls too far after stopping and you want a firmer stop, try checked.

6) Right Servo Port Drop-down

Choose the digital port for the right continuous servo (example: D1).

7) Right Servo Forward / Reverse / Stop Value Drop-downs

The right servo is often mounted as a mirror image of the left servo, so its “forward” direction may be reversed compared to the left side.

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A common default example for the right servo is:

• Forward: 1
• Reverse: 180
• Stop: 90

8) Test Buttons (Right)

Tests the Right servo using the selected Forward/Reverse/Stop values.

1. Connect your hardware
   Plug each continuous servo into the EZ-B:
   • Connect the signal wire to a digital port (example: Left = D0, Right = D1).
   • Make sure the servos have proper power (follow your EZ-B/servo power recommendations).
2. Add the skill to your ARC project
   In ARC go to: Project → Add Skill → Movement Panels → Continuous Servo Movement Panel.
3. Choose the correct ports in Settings
   Open the skill’s Settings and set:
   • Left Servo Port to the port your left servo is plugged into
   • Right Servo Port to the port your right servo is plugged into
4. Set a speed
   On the main window, move both speed sliders above 0% (start around 20–40%).
5. Test movement
   Press Forward. If the robot goes backward, you can fix it by:
   • Swapping the Left and Right ports in Settings, or
   • Adjusting the Forward/Reverse values for the side that is inverted, or
   • Physically swapping which servo is on the left/right side (depending on your build)

• 1 x EZ-B I/O Controller
• 2 x Continuous Servos

• Learn how ARC Movement Panels work: https://synthiam.com/Docs/ARC-Overview/movement-panels
• Servo technical overview: Servo Tutorial