Servo Component
The servo component supports “RC” or “hobby” servo motors. These are small motors with built-in potentiometer position sensors, enabling you to control the angular position of the servo precisely.
As servos can use a lot of power, drawing voltage away from a board, you should power your servo with its own power supply in most cases.
The following shows an example wiring diagram for a hobby servo wired to a pi board:
The colors of the servo wires in this diagram may not match your servo. Refer to your servo’s data sheet for wiring specifications.
Most robots with a servo need at least the following hardware:
- A board component that can run
viam-server - A servo
- A power supply for the board
- A power supply for the servo
Configuration
Tip
The Viam servo component supports hobby servos.
If your motor is coupled with an encoder, not a potentiometer, for position feedback, you should not configure it as a servo. Check your device’s data sheet and configure that type of servo as an encoded motor.
Supported servo models include:
| Model | Description |
|---|---|
fake | A model used for testing, with no physical hardware. |
gpio | A hobby servo wired to any model of board besides pi. |
pi | A hobby servo wired to a Raspberry Pi board. |
Click on the model names above for configuration information.
Control your servo with Viam’s client SDK libraries
To get started using Viam’s SDKs to connect to and control your robot, go to your robot’s page on the Viam app, navigate to the Code Sample tab, select your preferred programming language, and copy the sample code generated.
When executed, this sample code will create a connection to your robot as a client. Then control your robot programmatically by adding API method calls as shown in the following examples.
These examples assume you have a servo called "my_servo" configured as a component of your robot.
If your servo has a different name, change the name in the code.
Be sure to import the servo package for the SDK you are using:
from viam.components.servo import Servo
import (
"go.viam.com/rdk/components/servo"
)
API
The servo component supports the following methods:
| Method Name | Description |
|---|---|
| Move | Move the servo to the desired angle. |
| Position | Get the current angle of the servo. |
| Stop | Stop the servo. |
| DoCommand | Send or receive model-specific commands. |
Move
Move the servo to the desired angle in degrees.
Note
Support for continuous servos with the GPIO servo model is experimental. Stability is not guaranteed. Breaking changes are likely to occur, and occur often.
If you are using a continuous rotation servo, you can use the Move command, but instead of moving to a given position, the servo will start moving at a set speed.
The speed will be related to the “angle” you pass in as a linear approximation. 90 degrees represents stop, 91 to 180 represents counter-clockwise rotation from slowest to fastest, and 89 to 1 represents clockwise from slowest to fastest. It is recommended that you test your servo to determine the desired speed.
Parameters:
angle(int): The desired angle of the servo in degrees.extra(Optional[Mapping[str, Any]]): Extra options to pass to the underlying RPC call.timeout(Optional[float]): An option to set how long to wait (in seconds) before calling a time-out and closing the underlying RPC call.
Returns:
- None
For more information, see the Python SDK Docs.
my_servo = Servo.from_robot(robot=robot, name="my_servo")
# Move the servo from its origin to the desired angle of 10 degrees.
await my_servo.move(10)
# Move the servo from its origin to the desired angle of 90 degrees.
await my_servo.move(90)
Parameters:
ctx(Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.angleDeg(uint32): The desired angle of the servo in degrees.extra(map[string]interface{}): Extra options to pass to the underlying RPC call.
Returns:
- (error): An error, if one occurred.
For more information, see the Go SDK Docs.
myServo, err := servo.FromRobot(robot, "my_servo")
// Move the servo from its origin to the desired angle of 10 degrees.
myServo.Move(context.Background(), 10, nil)
// Move the servo from its origin to the desired angle of 90 degrees.
myServo.Move(context.Background(), 90, nil)
Position
Get the current set angle of the servo in degrees.
Parameters:
extra(Optional[Mapping[str, Any]]): Extra options to pass to the underlying RPC call.timeout(Optional[float]): An option to set how long to wait (in seconds) before calling a time-out and closing the underlying RPC call.
Returns:
- (int): The current set angle of the servo in degrees.
For more information, see the Python SDK Docs.
my_servo = Servo.from_robot(robot=robot, name="my_servo")
# Move the servo from its origin to the desired angle of 10 degrees.
await my_servo.move(10)
# Get the current set angle of the servo.
pos1 = await my_servo.get_position()
# Move the servo from its origin to the desired angle of 20 degrees.
await my_servo.move(20)
# Get the current set angle of the servo.
pos2 = await my_servo.get_position()
Parameters:
ctx(Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.extra(map[string]interface{}): Extra options to pass to the underlying RPC call.
Returns:
For more information, see the Go SDK Docs.
myServo, err := servo.FromRobot(robot, "my_servo")
// Move the servo from its origin to the desired angle of 10 degrees.
myServo.Move(context.Background(), 10, nil)
// Get the current set angle of the servo.
pos1, err = myServo.Position(context.Background(), nil)
// Move the servo from its origin to the desired angle of 20 degrees.
myServo.Move(context.Background(), 20, nil)
// Get the current set angle of the servo.
pos2, err = myServo.Position(context.Background(), nil)
Stop
Stop the servo from moving.
Parameters:
extra(Optional[Mapping[str, Any]]): Extra options to pass to the underlying RPC call.timeout(Optional[float]): An option to set how long to wait (in seconds) before calling a time-out and closing the underlying RPC call.
Returns:
- None.
For more information, see the Python SDK Docs.
my_servo = Servo.from_robot(robot=robot, name="my_servo")
# Move the servo from its origin to the desired angle of 10 degrees.
await my_servo.move(10)
# Stop the servo. It is assumed that the servo stops moving immediately.
await my_servo.stop()
Parameters:
ctx(Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.extra(map[string]interface{}): Extra options to pass to the underlying RPC call.
Returns:
- (error): An error, if one occurred.
For more information, see the Go SDK Docs.
myServo, err := servo.FromRobot(robot, "my_servo")
// Move the servo from its origin to the desired angle of 10 degrees.
myServo.Move(context.Background(), 10, nil)
// Stop the servo. It is assumed that the servo stops moving immediately.
myServo.Stop(context.Background(), nil)
DoCommand
Execute model-specific commands that are not otherwise defined by the component API.
For built-in models, model-specific commands are covered with each model’s documentation.
If you are implementing your own servo and add features that have no built-in API method, you can access them with DoCommand.
Parameters:
command(Dict[str, Any]): The command to execute.
Returns:
- (Dict[str, Any]): Result of the executed command.
my_servo = Servo.from_robot(robot, "my_servo")
command = {"cmd": "test", "data1": 500}
result = my_servo.do(command)
For more information, see the Python SDK Docs.
Parameters:
ctx(Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.cmd(map[string]interface{}): The command to execute.
Returns:
- (map[string]interface{}): Result of the executed command.
- (error): An error, if one occurred.
myServo, err := servo.FromRobot(robot, "my_servo")
command := map[string]interface{}{"cmd": "test", "data1": 500}
result, err := myServo.DoCommand(context.Background(), command)
For more information, see the Go SDK Code.
Troubleshooting
You can find additional assistance in the Troubleshooting section.
You can also ask questions in the Community Discord and we will be happy to help.
Next Steps
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