Phidget RC Servo.lvlib:RCServoSetTargetPosition.vi

If the RC servo motor is configured and RCServoTargetPosition is set, the controller will continuously try to reach targeted position.

The target position is bounded by RCServoMinPosition and RCServoMaxPosition.

Using the default settings this position will correspond to the rotation of the servo arm in degrees, for many standard RC servos.

If the RC servo motor is not engaged, then the position cannot be read.
The position can still be set while the RC servo motor is not engaged. Once engaged, the RC servo motor will snap to position, assuming it is not there already.
The units for RCServoTargetPosition, RCServoVelocityLimit, and RCServoAcceleration are configured by scaling the internal timing (set with RCServoMinPulseWidth and RCServoMaxPulseWidth) to a user specified range with RCServoMinPosition and RCServoMaxPosition.

Position and Pulse Width

An RC servo motor's position is controlled using a type of Pulse Width Modulation, sending voltage pulses of a given time span, or Pulse Width to the servo.
The servo translates the Pulse Width of the control signal to a corresponding position of the servo arm.
Knowing this, a servo's range of motion can be thought of in terms of a RCServoMinPulseWidth and a RCServoMaxPulseWidth corresponding to range of pulse widths that produce the servo arm's full range of movement.

In Phidget22, you can adjust the RCServoMinPulseWidth and RCServoMaxPulseWidth stored by the library to match the desired range of movement you expect from your servo.

Since directly setting the timing of RC servo pulse widths is not very intuitive for most purpses, we map these pulse widths to a user-defied Minimum and Maximum Position.This allows you to define the servo's position in terms best suited to your application, such as degrees, fractions of a rotation, or even some measure of speed for a continuous-rotation servo.
By setting the servo's RCServoTargetPosition to RCServoMaxPosition, the controller will send pulses of RCServoMaxPulseWidth to the servo.
- Similarly, RCServoMinPosition will send pulses of RCServoMinPulseWidth to the servo
- RCServoMaxPosition can be set smaller than RCServoMinPosition to invert movement of the servo, if it helps your application.
Setting a RCServoTargetPosition will transate the position between RCServoMinPosition and RCServoMaxPosition to a corresponding Pulse Width between RCServoMinPulseWidth and RCServoMaxPulseWidth, in turn sending the servo arm to the desired position.
Setting RCServoVelocityLimit and RCServoAcceleration for your servo will limit the rate of change of the servo's position in terms of one UserUnit per second (or /s²). Here, a UserUnit is whatever distance is maked by the change of the RCServoTargetPosition by 1.0

Adjusting the Servo's Limits

To tune your program to a specific servo:

First adjust the servo's range of motion by setting the RCServoMaxPulseWidth and RCServoMinPulseWidth. You can use the default values for these (or the ones on your servo's datasheet) as a starting point.
Send the servo to RCServoMaxPosition and RCServoMinPosition to check the results. Repeat steps 1 and 2 as nessesarry.
Set the RCServoMaxPosition and RCServoMinPosition to match whatever numbers you find best suited to your application.

Phidget RC Servo.lvlib:RCServoSetTargetPosition.vi

cu64

Device In

Device # Identification

cerrcodeclst

error in (no error)

error in can accept error information wired from VIs previously called.

cbool

status

status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.

Right-click the error in control on the front panel and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

ci32

code

code is the error or warning code.

Right-click the error in control on the front panel and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

cstr

source

source describes the origin of the error or warning.

Right-click the error in control on the front panel and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

cdbl

Target Position

The position value

1000_0 (ver: 200, 201) RC Servo Motor Controller: Must be set

1000_0 (ver: 300, 312) RC Servo Motor Controller: Must be set

1000_0 (ver: 313) RC Servo Motor Controller: Must be set

1001_0 (ver: 200, 201) RC Servo Motor Controller: Must be set

1001_0 (ver: 300, 302, 312) RC Servo Motor Controller: Must be set

1001_0 (ver: 313) RC Servo Motor Controller: Must be set

1061_0 (ver: 100) RC Servo Motor Controller: Must be set

1061_0 (ver: 200) RC Servo Motor Controller: Must be set

1061_1 (ver: 300, 301, 302, 303, 304) RC Servo Motor Controller: Must be set

1066_0 (ver: 100) RC Servo Motor Controller: Must be set

1066_1 (ver: 100, 101) RC Servo Motor Controller: Must be set

RCC0004_0 (ver: 400) RC Servo Motor Controller: Must be set

RCC1000_0 (ver: 106) RC Servo Motor Controller: Must be set

RCC1000_0 (ver: 110, 111, 120, 121) RC Servo Motor Controller: Must be set

RCC1000_1 (ver: 200) RC Servo Motor Controller: Default: 90

iu64

Device Out

Same as Device In

ierrcodeclst

error out

error out passes error or warning information out of a VI to be used by other VIs.

ibool

status

status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.

Right-click the error out control on the front panel and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

ii32

code

code is the error or warning code.

Right-click the error out control on the front panel and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

istr

source

source describes the origin of the error or warning.

Right-click the error out control on the front panel and select Explain Error or Explain Warning from the shortcut menu for more information about the error.