How many motors

Technical Support
1

Issue:

Section 6.1 “Features” in the web page for the DYNAMIXEL Shield for Arduino states that “Up to 16 DYNAMIXEL’s can be controlled”.

Despite this, I have seen many tutorials in which Arduino-controlled DYNAMIXEL servos are used to actuate hexapod robots - a project I wish to do myself. The issue is that such a task requires 18 servos. I am wondering how I can accomplish this task? Are there better ways to control 18 x AX-12A servos? If I use 6 x 2XL430-W250-T and 6 x XL430-W250-T, then would that be equivalent to controlling just 12 servos, in other words, within the capabilities of the DYNAMIXEL shield?

Thank you

DYNAMIXEL Servo:

AX-12A

DYNAMIXEL Controller:

Arduino
DYNAMIXEL Shield

Software Interface:

Arduino IDE

2

@SNAPIR

In practice, I have found that DXLs should not be hooked up into a daisy chain more than 4 DXLs long, if not the far/last DXL may not get enough voltage/current to operate properly.

As the DXL Shield has 3 X3P TTL connectors, and if you need to use 12 DXLs, you should be able to hook 3 mini-chains of 4 DXLs long for each OK. No need for anything extra.

DXL_Shield

If you want to use 18 DXLs, then you will need a second power supply and a custom made DXL Power Cable as shown below

CustonPowerCable_X3P

It happens to convert a barrel connector to X3P connector - but you can adjust for other type of battery connector as needed. Also you’ll need to solder the wire splicing areas and some shrink-tubing of course (not shown in my picture).

That X3P Hub is critical and it is “out of stock” from ROBOTIS e-shop (as expected :grinning:).

The X3P end of this Custom Power cable goes into Connector 1 of the X3P Hub.

For Connectors 2, 3 and 4 of this X3P hub, you can hook up 3 mini chains of 4 DXLs each using regular X3P cables - so that takes care of 12 DXLs out of your 18 DXLs.

A regular X3P cable from DXL Shield can go to Connector 5 of the X3P Hub - so that the Arduino Board itself can see the DXLs powered out of this X3P hub (so you cannot skip this step).

For the remaining 2 X3P Connectors on the DXL shield, you can put up 2 mini-chains of 4 DXLs each, so that brings the total DXLs to 20 - so your project should be covered.

Come to think of it, you can use one X3P Hub + 1 Power Supply for each side of your Hexapod (4 DXLs per leg), and then connect both X3P Hubs back to the DXL Shield and then you’ve got plenty of leeway for DXL power and control. Also you can use the last X3P connector on the DXL Shield for a 2XL-430 used as a pan-tilt platform for your camera!

You are “lucky” that all your DXLs use the same VDD voltage of 11.1~12 V. If they were of different types >> more complications!