Servo Bricklet 2.0¶

Features¶

• Controls up to 10 RC Servos
• Brushless motors with external ESC also controllable
• Adjustable Period and pulse width
• Uses motion planning to reach position with smooth motion
• Velocity and acceleration/deceleration can be configured
• Current measurement for each individual channel

Description¶

The Servo Bricklet is able to control up to 10 RC servos. With the provided API for many programming languages you can control the position, velocity and acceleration/deceleration of the connected servos. Motion planning is used to reach a position with smooth motion. The current-draw of each servo can be measured independently. Additionally output PWM (pulse width and period) is configurable for each servo.

The servos are powered by an external power supply (black connector). The voltage from this connector is directly connected to the servos.

Technical Specifications¶

* configurable per servo channel

Resources¶

• Schematic (Download)
• Outline and drilling plan (Download)
• Source code and design files (Download)
• 3D model (View online | Download: STEP, FreeCAD)

Connectivity¶

The following picture depicts the different connection possibilities of the Servo Bricklet 2.0.

Test your Servo Bricklet 2.0¶

To test a Servo Bricklet 2.0 you need to have Brick Daemon and Brick Viewer installed. Brick Daemon acts as a proxy between the USB interface of the Bricks and the API bindings. Brick Viewer connects to Brick Daemon. It helps to figure out basic information about the connected Bricks and Bricklets and allows to test them.

Connect a RC servo to a port of the Brick and a suitable power supply.

If you connect the Brick to the PC over USB, you should see a new tab named "Servo Bricklet 2.0" in the Brick Viewer after a moment. Select this tab.

In the left part of the tab you can select the servo to control. You can enable and disable it, configure the PWM pulse width and define the degree range. Additionally you can see the current consumption of the servo. Below there are four sliders to control the position, velocity and acceleration of the servo. The fourth slider can be used to change the period of the PWM (see Configure Servo PWM for more information).

On the right side you can see the input voltage. Below are graphical representations for the state of each servo.

After this test you can go on with writing your own application. See the Programming Interface section for the API of the Servo Bricklet 2.0 and examples in different programming languages.

Configure Servo PWM¶

Typically you control a RC servo by a PWM signal with a period of 20ms and an on-time of 1ms to 2ms depending on the position you want to achieve. However, some servos do not work properly with these standard settings. Therefore we provide a fully configurable PWM.

The default value for the period is 19.5ms. This period worked on all servos we could get our fingers on (20ms did not work with some of the cheaper Chinese servos). If the datasheet of your servo does specify a preferred period, use it. But it is likely that you don't have to change this value.

More interesting is the minimum and maximum pulse width. The default pulse width is 1ms to 2ms. Most servos can however rotate further when minimum/maximum pulse width is decreased/increased. If your servo comes with a datasheet we recommend to use the values described in there. If you don't have a datasheet you can try to incrementally extend the pulse width until the servo starts to rattle. Use the biggest pulse width that does not produce rattling.

Usage of ESCs to drive brushless motors¶

With this Brick you can control up to 10 brushless motors by using external Electronic Speed Controllers (ESC). Simply connect the brushless motor to the ESC and the ESC to the Servo Brick. With this construction the maximum brushless motor current only depends on your selected ESC.

Connect other Hardware¶

Also other hardware like fan cooler with PWM input can be controlled.

You can use 12V fans or 24V fans and connect the 12V/24V to to the black input voltage connector. The control PWM input of the fan must however accept 0V low level und 5V high level. The majority of 12V/24V PWM controllable fans work this way, but check the datasheet of of the fan before you connect it.

Coming Soon: Image/Video + example configuration

Case¶

TBD

Programming Interface¶

See Programming Interface for a detailed description.

FAQ¶