DIGILENT PmodCON3 R-C Servo Connectors Owner’s Manual

DIGILENT PmodCON3 R-C Servo Connectors

PmodCON3TM Reference Manual

• Revised April 15, 2016. This manual applies to the PmodCON3 rev. C
• The Digilent PmodCON3 (Revision C) is a module designed to interface with up to four small servo motors. These motors can deliver torque ranging from 50 to 300 ounce/inches and are commonly used in radio-controlled airplanes, cars, and mechatronics projects.

Features:

• Four standard 3-wire servo motor connectors
• Specification Type 1
• Example code available in resource center

Functional Description:

The PmodCON3 allows easy interface between any Digilent system board and a standard 3-wire servo motor. The servo motor requires a signal wire, a positive power supply wire, and a ground power supply wire. The power supply can be sourced from either the system board or an external power source using screw terminals with the appropriate jumper block setting.

Interfacing with the Pmod:

Servo Control Diagram:

Physical Dimensions:

The pins on the pin header are spaced 100 mil apart. The PCB is 1.0 inches long on the sides parallel to the pins on the pin header and 0.8 inches long on the sides perpendicular to the pin header.

Overview

The Digilent PmodCON3 (Revision C) can be used to easily interface with up to four small servo motors that deliver anywhere from 50 to 300 ounce/inches of torque, such as those used in radio controlled airplanes or cars, as well as some mechatronics projects

Features include

• Four standard 3-wire servo motor connectors
• Easily interface with Digilent system boards
• Flexible power delivery to servos
• Small PCB size for flexible designs 1.0 in × 0.8 in (2.5 cm × 2.0 cm)
• 6-pin Pmod port with GPIO interface
• Follows Digilent Pmod Interface Specification Type 1
• Example code available in resource center

Functional Description

The PmodCON3 allows any Digilent system board to easily interface with a standard 3-wire servo motor consisting of a signal, positive power supply, and ground power supply wires. The power supply can be sourced either from the system board or an external power source via screw terminals by selecting the appropriate setting on the jumper block.

Interfacing with the Pmod

The PmodCON3 communicates with the host board via one of the four GPIO pins (the first four pins on the 1×6 header). As mentioned in the Functional Description, it is also possible to select how to power an attached servo motor by setting the shorting block in the appropriate jumper configuration.

Header J1

Pin Number| Description
1| Servo P1
2| Servo P2
3| Servo P3
4| Servo P4
5| Ground
6| VCC
Jumper JP1

Jumper Setting| Description
VCC| The voltage source for the servos comes from VCC and Ground
VE| The voltage source for the servos come from the + and – screw terminals
|
|
|
|

Table 1. Connector J1- Pin Descriptions as labeled on the Pmod.

• Standard servo motors use a potentiometer to adjust the angle at which their central shaft rotates to. In order to adjust the rotation angle, the motor generally needs to receive a “high” voltage pulse that ranges from 1 millisecond to 2 milliseconds, with 1.5 milliseconds as the “neutral” value. These values typically correspond to 0 degrees, 180 degrees, and 90 degrees, respectively, although depending on the manufacturer of the servo motor, these angles may vary. A signal that is either too narrow or too wide for a servo will cause the servo to try to go beyond its rotational range and can damage the servo. Always check the manufacturer’s instructions for a servo’s rotational range.
  

• Because the pulse length is relatively long, any of the IO pins on a Digilent system board are capable of driving a servo motor. However, in order to have the servo motor maintain its given angle, a refresh pulse of the same (or new) angle will need to be provided to the servo motor periodically (20 milliseconds is a safe value). When using the Servo library available from Digilent, the refresh pulse and the pulse width are automatically taken care of, allowing the user to simply give the desired angle for the servo motor to rotate to.

Physical Dimensions

The pins on the pin header are spaced 100 mil apart. The PCB is 1.0 inches long on the sides parallel to the pins on the pin header and 0.8 inches long on the sides perpendicular to the pin header.

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References

• Digilent – Start Smart, Build Brilliant.

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