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Sabertooth And Servo Control

Assistance Requested

Help Jayutmb with their question and receive $10 of EZ-Credit to get more robots and parts from our store. The following information was provided about their previous efforts searching tutorials for a resolution.

Jayutmb claims to have checked these sources:
 
#1

Is there a way ( and sorry if this comes off as a dumb question to even ask...) to have the EZB control the DC motors connected to my sabertooth as servos ? or a more controllable form other than sendserial ?

I have found a few conversations, tutorials and activities that may help with your question. Take a look at these links. I've sorted them by what I believe to be most relevant but that is not always the case as I'm still learning.


Also, consider reviewing the Learn section for informative lessons and activities. Check it out!


#2

Although the Sabertooth has an R/C mode that supposedly emulates a servo (I assume a modified 360 rotational servo) it doesn't seem to work with EZ-B servo controls. So simple answer, no.

Parallax HB25 motor controllers do work just like 360 servos. They need an initialization script to work properly, but otherwise they will drive a single 25 amp motor just like a servo. See http://www.ez-robot.com/Community/Forum/Thread?threadId=6848 for details on initialization.

Alan

#3

@Alan... I could be wrong, but it sounds like @Jayutmb wants his DC motors to have position control like regular servos.... I'll let you answer it then....

#4

@Jayutmb, the answer is yes. By it's self te Sabertooth has no speed and position control. Dimention Engineering has a daughter board for the Sabertooth called Kangaroo X2. It adapts to the control side of the Sabertooth and gives the Sabertooth complete control like a servo. You need to use simple serial commands sent through EZB's Uart ports or the serial feature of the digital ports. After you tune the Kangaroo to your DC motor it works great. Tuning can be a little touch and go depending on your setup. Also be advised that you need to add a feedback device like a Pot or encoder and limit switches to your setup to let the Kangaroo know where your motor is at any given time.

Look here:

Kangaroo X2

User-inserted image

#5

thx guys Smile

#6

No problem @Jayutmb. If you go the Kangaroo route you have to make sure you have your whole system setup and secure before you try to do an Auto Tune. The Kangaroo will not tune without a feedback device. You don't really need limit switches. Even though the Roo needs to know the end of travel points you can also set it to see then two other ways. You can use physical stops like a block or a wall or if you can manually move the motor you can teach the unit where the stop points are. If your using a worm gear motor you may be unable to move the motor shaft by hand to use the Teaching method.

Once you get a successful tune you should have a very nice system that will run smooth for you, be very precise and be able to scene resistance and apply more motor power when needed to keep the speed up.

Commands are very simple. There has been a bunch of threads here on this forum showing examples by me, Lumpy and Toymaker of how to let EZB send the Simple Sireal Commands to the Roo. Here's a couple quick examples of how to send it through both the Uart port and a serial (Digital) port:

Code:


SendSerial(D0, 9600, "1,p2450 s300", 0x0d)

uartwrite(0,0,"D,start",0x0d)



Hope this helps

Dave Schulpiius Smile

#7

Friends... Finally I could learn how to Tune the Sabertooh/Kangaroo combo.
I got the Motor with encoder.. and all.
now I really need your ligth! how do I wire it to EZ-b ?
and How do I script it ? what command do I use ? If you have some examples would be great! i'm almost giving up this set up...
My intention is to use it to drive my R2 Dome in order to make it follow the camera, just like we do with the servos..
Help me masters! you're my only hope!

#8

@Tevans,

See this thread http://www.ez-robot.com/Community/Forum/Thread?threadId=8740&page=5

@castlephelps got a Sabertooth/Kangaroo combo working in R/C mode, so you use it just like a servo.

Alan