Controlling a four-axis robot arm

Gentle Touch

© Lead Image © marc heriche,

© Lead Image © marc heriche,

Article from Issue 226/2019

Learn the basics of robotics with a Raspberry Pi and a PiXtend controller.

Robotics might seem like a daunting subject to tackle, but a Raspberry Pi, a PiXtend module, Codesys control software, and a bit of Structured Text (ST) programming are all you need to get started in this compelling discipline. In this article, I describe how to set up and program a robot arm.

For this project, I opted for the four-axis robot arm by SainSmart [1]; it has a good price-to-performance ratio and a large working range. Simple hobby servos let the robot arm equipped with a simple gripper [2] move objects. The Thingiverse website provides the 3D printer files for printing the gripper [3]; alternatively, you can purchase the gripper on Amazon [4]. The gripper also is driven by a servo and requires a PWM signal for control. For more information on servos, see the box "How Servos Work."

The best way to keep track of the motors is to label each one (Table 1). Figure 2 shows the robot with the gripper, and the wiring diagram in Figure 3 shows how to connect the individual motors. Please note that hobby servos can handle a maximum of 6V.


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