RoboCon

# Servos

Servos are a bit like motors, except their position is fixed. This is useful for building an arm mechanism that grabs cubes, or anything else that has fixed states that it needs to be in.

Similarly to motors, the position of a servo is expressed as a percentage. This can be negative.

Servos are plugged into the Servo ports on the BrainBox. Servo 0 represents servo 0, Servo 1 is servo 1, etc. They are numbered from 0 to 3.

# Python

You can control servos using the servos property of the Robot object. To set the first servo to the 50% position use:

R.servos[0] = 50

To control the fourth servo instead, replace servos[0] with servos[3].

TIP

Don't forget to setup the servo pin with R.servos[0].mode = robot.PWM_SERVO before you control any servos! Otherwise the servos won't be setup, so you can't control them yet. Write this line for every servo you wish to control (replacing the 0 with the servo port you're using).

Here's a more complete example:

import robot

R = robot.Robot()
R.servos[0].mode = robot.PWM_SERVO
R.servos[3].mode = robot.PWM_SERVO

# set servo 0 to the 50% position
R.servos[0] = 50

# set servo 3 to the -100% position
R.servos[3] = -100

# set servos 0 & 3 to the default positions
R.servos[0] = 0
R.servos[3] = 0

# Blockly

Blocks for controlling servos can be found in the Movement section.

# Default positions

Servos default to a starting position 1/2 way through their travel, for some uses teams may need to start with a different resting position to ensure their robot fits within the set sizes, you can set the position that the servo holds while waiting for the start button to be pressed by initilizing the robot object with servo_defaults=((servo_number,position)...,(servo_number,position))

E.g. to set Servo1 to 100% and Servo3 to 50% use

import robot

servo_values = {
    1: 100,
    2: 50,
    3: -100
}

R = robot.Robot(servo_defaults=servo_values)

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