Robotis Frequently Asked Questions (FAQ's):

Dynamixel FAQ's
Bioloid FAQ's

* Known errors in Dynamixel AX Series Manual:

  • p9 of 38 "the LED blinks twice to confirm its connection" - the LED's on the AX-12 only flash once, the LED's on the DX modules flash twice.
  • p37 of 38 - the part numbers for Molex connectors for AX-12 are for 4 pin not 3 pin. These should be Male 22-03-5035 and Female 50-37-5033.

NB. Within our Forum there is a Topic on "Dynamixel AX series issues", this may be have more recent information on errors found in the document, it can be viewed our contributed to here ....

Dynamixel FAQ's

NB. In Jan06 the following changes were made to the AX-12's default settings:
Addr2: Version of Firmware- was 17(0x11) and now is 18 (0x12)
Addr4: Baudrate- was 34 (57,143bps=57,600bps) and now is 1 (1,000,000bps)
Addr11: Highest Limit Temperature- was 85°C and now is 70°C.

How many Dynamixel modules can be daisy-chained?
What are the default settings of a factory supplied device?
Why does the AX-12 make an annoying 'whining' sound?

 

Q1.
 How many AI modules can be daisy-chained?
 
254 AI modules can be connected to a single serial channel - of course the total current that can be delivered by the source should be taken into consideration before more that 31 are connected simultaneously.
Q2.
What are the default settings of a factory supplied device?
 
To list these here would be too long, it would be better if you consulted the Dynamixel Manual, the Default settings can be in the table on p12.
Q3.
Why does the AX-12 make an annoying 'whining' sound?
 

To understand why this occurs it is important to understand how the AX-12 is positioned. The 'whining' noise occurs when you tell an AX-12 to goto a position a specific position, i.e. you say goto X where X is between 0 and 1023.

  • The AX-12 can be positioned over a 300 degree range, i.e. +/- 150 degrees from centre position.
  • Attached to the AX-12's shaft is a potentiometer - this is in essence a variable resistor. When you pass a current through this a different voltage will be output at different positions.
  • This voltage is then fed into a microcontroller (mcu) on its Analog to Digital (A2D) port - this converts the voltage to a number that the mcu uses.
  • The A2D is 10bit, this means there is 2^10 or 1024 positions that can be identified, 0 to 1023 with 512 being the middle position.
  • Now, 300 degrees is broken up into 1024 pieces (this is known as resolution) - 300/1024=0.293.
  • So, each increment of the number between 0 and 1023 is equivalent to 0.293 degrees.

This is the problem - if you say goto position 250, this equates to 73.242 degrees. This is practically unachievable to be so accurate. The AX-12 will move its shaft to the correct position but due to external shaft movement, electrical noise, etc., it can't get exactly where it wants to. So, it keeps trying - the side affect of this is that the AX-12 keeps trying to position itself (constantly) and keeps making the 'whining' noise.

To summarise, there is nothing wrong with the motors if they whine, its just very annoying. But, one of our Bioloid users has come up with a very clever work around, please see his forum entry for more details.


Bioloid FAQ's

Special note on Bioloid Assembly with the AX-12
What are the operating modes of the CM-5?
I'm following the procedure from the User Manual but the Battery won't recharge, i.e. the POWER LED doesn't FLASH to indicate charging?

 

Q1.
 What are the operating modes of the CM-5?
 

The CM-5 has 4 Operating Modes:

  1. Standby,
  2. Manage,
  3. Program, and
  4. Play.
  • There are 3 LED's on the back of the CM-5 that shows what operating mode the CM-5 is in, i.e. Manage, Program & Play.
  • When ANY of the LED's are ON constantly, then the CM-5 is in that mode.
  • When ANY of these LED's are FLASHING then the CM-5 is in Standby mode.
Q2.
I'm following the procedure from the User Manual but the Battery won't recharge, i.e. the POWER LED doesn't FLASH to indicate charging?
 

To charge the internal NiMH Battery the CM-5 must be in STANDBY Mode and you must press the 'U' (or UP) button.

If you are doing this and the POWER LED is not FLASHING then chances are the internal fuse is blown. Try replacing this was the spare and this should solve your problems.