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Sudo'S Guide To Dynamixels

PLEASE NOTE: THIS GUIDE IS OUTDATED. BADLY. (remind me later to fix this and spiff it up a bit, please)

So, you finally have your EZ-B v4. You love it already, and you're ready to hook this baby up to some sort of Dynamixel powered creation. You go to plug everything in, and - wait. You have no idea how to set those Dynamixels up.

Well, I do, and I'll show you how.

SECTION 1: GETTING TO KNOW DYNAMIXELS

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Dynamixels are intelligent servos that can track not only position, but temperature, speed, and load. The servo can automagically shut itself of incase of a failure. These servos are also incredibly strong. But there's one feature in particular that is useful, but at the same time a little hard to wrap your head around. In this section, we will cover daisy chaining and other features of the AX-12A Dynamixel; however, most of the servos in the Dynamixel family work exactly alike, so this guide can help you with most models.

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On the back of all of your Dynamixels, you will notice a couple things. A place for a bolt, a light, two wire ports, and the ID. Lets go over all of them so you know what they do:

Light - Blinks once when turning on. If the light is flashing, there is a failure of some sort.

Screw hole - Allows you to attach the Dynamixel to a bracket.

Wire ports - Allows you to connect to other Dynamixels, in a long strand of servos, both to and from other Dynamixels. This means both ports work the same way, which means it doesn't matter which side is plugged in. (see image below)

ID - What the EZ-B and ARC address the Dynamixel as.

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PART 2: CONNECTING YOUR DYNAMIXELS TO THE EZ-B

All Dynamixels must plug into port D5 in order to properly work. This means that all of your Dynamixels must plug into one port. If you have more than one strand of connectable Dynamixels, you will have to use a Dynamixel splitter hub, like this one here:

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You can either run a cable to the EZ-B via a power base or via the powered splitter. I advise that you use only one, as using both at once can brown out the EZ-B.

Q: So, now that that's done, what power supply do I use? Mains or a battery pack?

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A: Both will work just fine. Just make sure you have an adequate power supply at around 10v.

"But wait!" you scream. "Dynamixels can run at 9v-12v! Why 10v?"

Because voltage is gradually lost over time depending on how many servos you're running at once, as well as when the EZ-B is powered on. The more servos you have, the higher you should up your voltage to get a steady 10v overall.

So, if you have power running to the EZ-B, Dynamixels set up to port D5 (as well as the optional splitter) you should have something resembling this:

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Now that you're powered on, lets move into ARC and get your Dynamixels running.

PART 3: OPERATING THE DYNAMIXELS WITH ARC

Connect to your EZ-B as usual (We won't be covering connections in this guide). Bring up a servo control panel and go to the servo configuration screen as shown below.

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Click the Dynamixel box and scroll down until you see the ID of the Dynamixel you want to move (the ID on the back of the servo). In this demonstration, we'll be selecting Dynamixel AX18.

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Select it and save the configuration. Congrats, you just set up your first Dynamixel in ARC! It should operate just like a normal servo. This applies to all servo control functions.

PART 4 (EXTRA): ASSIGNING A NEW ID TO BLANK SERVOS

When you buy a Dynamixel that doesn't come in the kit, the ID sticker will sometimes be blank, which means it hasn't be assigned a "real" ID. However, a tool in ARC can give Dynamixels a new ID.

First, open up the Dynamixel Config. control in ARC. You should see something similar to this:

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All blank servos are assigned ID 1. If you have a dynamixel with the ID 1 already, remove it before you proceed. Simply choose the new ID you want (in this case, AX18) and press execute. ARC will assign it a new ID. That's it, you're done! You can also write the ID on the blank tag if so desired.

GUIDE LAST UPDATED: 12/9/2014


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United Kingdom
#129  

@mcsdaver.

Thanks for your reply. Yeah I did see post #120 and that does look like fun. So I take it from what you said that the AX-12's cannot be used the same way as the other servos then? If that's the case then thats a real shame as like yourself, I would like to be able to use them as regular servos as well.

#130  

They work fine until you open AutoPosition and then they stop working. So setting up poses is a bit of a problem. The script in post #120 make them usable. I haven't tried it yet. I have tested AX-12 servos and they do work. Plug one into D5 and setup a servo control. Make sure to set it to AX-12 servo and the id number of the servo. You can chain many of them together. I think DJ said 50 of them at once.

#131  

@OldBotBuilder Have you gotten the EZ-B to talk to the Bioloid computer?

United Kingdom
#132  

@mcsdaver.

That's great. Thanks for the summery. So using them in an Auto Position is the only issue with using the AX-12's then at the moment then. That's good to know. I just wanted to ask one more question. How are scripts written to use these servos? For example...

Servo(D0,20)
ServoSpeed(D0,1)
Sleep(5000)
Servo(D0,90)

how would this example be written for a Dynamixel servo?

One other thing. What are the voltage specs for the Dynamixel/Robotis touch sensors (as I can't seem to find much info on them) and can they be used with the EZ-B v4?

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Thanks.

#133  

Hi @mtiberia

Thank you for developing the script to capture the pose of a robot using dynamixel servos and EZ-B. Nice work.

I have tried to connect 4 dynamixel servos into EZ-B and the script did found the 4 servos, but when it "start recording" EZ-B keep saying "oops i need to read the position again" and then says "reading", and the saying is repeating again and again.

Yet, there is no saying of "Move to next position please".

FYI, I have create a .txt file as per your instruction and placed the file address information in the ENTER A FILE NAME window.

Could you help me, please :)

PRO
Belgium
#134  

steve G

its 5 volt for the touch sensor.

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all ports are 5 volts

United Kingdom
#135  

Thanks Nomad.

PRO
Belgium
#136  

i have robotis installed on my pc.then you have all info you need. the above pic is port 3 on the left and port 4 on the right. left side is port 1 and 2 and on the right side is port 5 and 6 there are little marks on each port.

port1=l port2:ll port3=lll port4=llll port5=lllll port6=llllll