On the cutting-edge landscape of robotics, versatility and connectivity are key. Here at ROBOTIS, we are proud to provide solutions that embrace these ideals, particularly with our DYNAMIXEL Smart Servos. One of the standout features of the DYNAMIXEL family is their ability to be daisy chained together, to create multi-actuator networks along the length of a single cable. This capability not only simplifies the configuration and control of multiple servos, but it also opens up a wealth of possibilities for the creation of complex and sophisticated robotic systems.

 

In this blog post, we wanted to share some handy tips, clever tricks, and effective techniques  for methods of daisy chaining DYNAMIXEL servos (and maybe even more). Whether you're a seasoned roboticist or a beginner dabbling in your first projects, understanding this concept can be a game-changer. We'll discuss what exactly daisy chaining is, the benefits it offers, and provide practical guidance on how you can use this feature when designing and building your next robotic project. 

DYNAMIXEL IDs

Before jumping into the discussion on daisy chaining, It’s best to start off with a quick introduction to DYNAMIXEL ID assignment, and how this relates to the setup and usage of daisy chained actuators. Each DYNAMIXEL servo contains an ID number saved to it’s internal memory that the actuator uses to identify itself on the DYNAMIXEL network, and to determine which instructions it should execute when they are received. Each DYNAMIXEL servo on a shared daisy chain must have a unique ID assigned to it, otherwise communication may be disrupted. As each DYNAMIXEL is assigned a default value of 1 when the actuators are new, the first thing that you’ll need to do to add them to the daisy chain is to change the ID to ensure that they don’t overlap with each other. The simplest way to do this is with the ID Inspection tool in our DYNAMIXEL Wizard configuration software. With that recap out of the way, it’s time for us to move on to the main topic of today’s discussion:

Daisy Chaining Basics

As per usual, it's best to start off with the fundamentals: Daisy chaining is a term derived from the way flowers can be linked together by their stems, used in this context to describe a configuration where devices are connected in sequence or in a chain. 

 

In the context of DYNAMIXEL servos, daisy chaining refers to the ability to link multiple servos together and control the entire chain through a single communications line. 

This configuration has several key advantages. Firstly, it simplifies cabling and reduces clutter, as each servo does not need to be individually connected to the main controller. Secondly, by using the unique ID assigned to each DYNAMIXEL servo, you can control each servo independently, even when they're chained together. This combination of simplicity and powerful functionality is what sets DYNAMIXEL servos apart from standard servo motors. To leverage the full potential of this powerful feature, you need to understand the best practices for daisy chaining DYNAMIXEL servos. 

Daisy Chaining Best Practices

The first, and most important consideration when daisy chaining multiple DYNAMIXEL actuators is to ensure that the power supply you’re using for your daisy chain can safely supply enough power to drive the daisy chain. However, there’s a second thing to keep in mind to maximize your daisy chain performance: secondary power inputs. For longer daisy chains and for applications where the entire chain is expected to operate at high levels of output, the chain may not be able to safely pass full current to the servos at the far end. This can result in reduced torque output, or even unexpected shutdowns of the furthest actuators on the daisy chain. In order to eliminate this issue, the best practice is to add additional power lines from the main power supply to some of the actuators further along the daisy chain. These additional power inputs are usually only needed every 3-7 actuators, depending on how heavy the expected usage for these actuators is. For most smaller daisy chains, this won’t be required at all, but it’s important to keep this in mind, in order to avoid any possible issues that could crop up with a longer chain. It’s also possible to extend this basic daisy chain functionality to allow the usage of TTL and RS485 DYNAMIXEL servos on the same daisy chain through the use of the DYNAMIXEL Communications Bridge. This additional accessory converts between the TTL and RS485 serial protocols and allows DYNAMIXELs to coordinate between them seamlessly, opening the door to our first example of more advanced daisy chain functionality.

Mixed Operating Voltages

Aside from the basic layout mentioned in the last section, it’s possible to connect DYNAMIXEL servos utilizing mixed operating voltages, allowing the creation of single DYNAMIXEL networks that control both the largest and smallest DYNAMIXELs available simultaneously. It’s important to take proper care when implementing a network like this, as improper setup can result in damage or destruction of your DYNAMIXEL servos! The critical step in setting up a network like this is to separate the connected power supplies into two complete separate electrical circuits, to prevent different voltages from being supplied to DYNAMIXELs not designed to run with that input.

 

If we still maintain the continuous unbroken serial communications connection, we can address each connected DYNAMIXEL no matter what power supply they are being driven from. This provides us the capability of operating any combination of DYNAMIXEL servos on a single network, so we can meet the needs of even the most demanding design requirements.

 

Daisy chaining DYNAMIXEL servos offers numerous benefits and opens up a world of opportunities in terms of versatility, functionality, and design possibilities. However, this also adds a layer of complexity when it comes to set up and configuration. It is critical to remember that taking the time to carefully plan out your system, considering the technical requirements and following best practices, can save you from potential issues down the line. 

 

Our goal in this blog was to provide you with a comprehensive understanding of daisy chaining, and how it can be strategically used in your DYNAMIXEL servo systems. With this knowledge, we hope you are now equipped to exploit the full potential of daisy chaining in your future robotics projects. As always, we at ROBOTIS are dedicated to supporting our community of creative minds, and we’re excited to see the innovative ways you’ll leverage this feature in your ventures into the world of robotics. The possibilities await – Happy chaining!