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Subject: 
Re: different output power at different ports?
Newsgroups: 
lugnet.robotics.rcx, lugnet.robotics.rcx.robolab
Date: 
Thu, 14 Jul 2005 15:14:27 GMT
Viewed: 
8527 times
  
On 7/14/05, Elizabeth Mabrey <emabrey@storming-robots.com> wrote:
Without any precious hardware verification, this is what I did:
- symptom: motor C was not able to make turn as well as motor A can
- troubleshooting steps:
  a) to ensure even load on both motor ports, I removed all other
attachments, and left the robot to a simple tankbot with a single light
sensor to follow slight curves in order to make it easier to visualize the
difference.
  b) at program level, both are set to be the same power level, of course.
  c) interchange motors between port A and C, same symptom, so the problem
is not the motor itself
  d) change fresh batteries, drain the firmware, redownload the firmware,
same symptom

Okay - did you try a simple program going in a straight line, and
check how much it veered after a few meters?

Unfortunately - it does not sound an entirely unlikely problem - if
there are variations between the h-bridges (general manufacturing
variations etc) - then you may get this. Neithor motors, nor outputs
can be relied on for very accurate output - my answer (and a few
others) to this - to eliminate veer is to use an adder subtractor
drive (these are also used for crane systems as well).

Have a look at this:
http://orionrobots.co.uk/tiki-index.php?page=Adder+Subtractor+Drive

Cheers,
Orion
--
http://orionrobots.co.uk - Build Robots

Online Castle Building RPG -
http://www.darkthrone.com/recruit.dt?uid=V30311I30328J30379X30379E30260X30277



Message has 1 Reply:
  Re: different output power at different ports?
 
(...) This sounds to me like a good tactic. Your program might have some issue with turning in one direction vs another. (...) I also have trouble believing variations in parts (except the motors themselves) will cause this much difference. Ralph (19 years ago, 14-Jul-05, to lugnet.robotics.rcx, lugnet.robotics.rcx.robolab)

Message is in Reply To:
  RE: different output power at different ports?
 
(...) Without any precious hardware verification, this is what I did: - symptom: motor C was not able to make turn as well as motor A can - troubleshooting steps: a) to ensure even load on both motor ports, I removed all other attachments, and left (...) (19 years ago, 14-Jul-05, to lugnet.robotics.rcx, lugnet.robotics.rcx.robolab)

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