Your robotic problems solved here.
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index.php/magazine/article/january2016_MrRoboto.
simple commands that will
automatically figure out the
speed and direction values
for each motor to make the
turn. Some even allow
dynamic feedback from
wheel encoders to make
sure that the motors go the
speed you want them to go.
Most — if not all —
offboard motor controllers
will monitor current and
temperature, and shut
down the drivers to avoid
damage due to
overheating; they may also
notify the main controller
of the status of the board
in those cases. A good
motor controller will allow
you to configure them either with your computer or by
using setup programs you put on your main robot
controller. Premium motor controllers will also watch your
battery pack to avoid over-discharging them or pulling too
much current. This is essential with LiPo batteries since you
will kill such a battery if its charge gets too low.
The crowning touch for using an offboard motor
controller is that it can provide
regulated power to your
microcontroller. This means you
will only need one battery instead
of two: one for your motors and
one for your controller. Radio
control (RC) hobbyists are already
used to this feature in their RC
motor controllers. As it turns out, I
am replacing one of my combat
robot’s (yes, it is autonomous, not
RC) main brain and will be moving
to an offboard full motor
controller.
I chose the Pololu TReX Jr
controller ($60) because it could
deal with two bi-directional motors
(and a single direction one as a
bonus.) The TReX Jr has other
useful features like: 5V-24V power
input range; good for small
motors; serial command
connection; current limiting; and
the ability to switch to RC control
in an emergency. It is tiny too —
Well, that’s it for this time. I hope you were inspired,
and go out and make something new and fun for yourself!
As usual, keep those questions coming to
roboto@servomagazine.com and I’ll do my best to
answer them! SV
SERVO 01.2016 11
Figure 1.
Figure 2.
