8 SERVO 12.2014
Q. I am building a two-wheel balancing robot, but I’m not sure that a 2 x DC motor with encoder or a 2 x stepper motor is better for
that kind of robot. Also, should I use two batteries
(one for the motors and one for the Arduino circuit
and sensors) or just use one battery for both (with a
regulator for the sensors)?
— Jackie Su
A. I have actually fielded this question before in other places. The stepper motor seems to have a mystery or panache about it that just makes us
want to use it in our robots. Stepper motors have a
different driver configuration and control sequence
than DC motors do, and let's face it, they just sound
cool. A stepper motor is very good at moving precisely
to a chosen position and getting to the same exact
place every time. This kind of motor is also very good
at holding that position firmly, without using complex
PID algorithms and specialized encoding schemes.
( Wait for it ...)
A stepper motor is not very fast (compared to a DC
motor — either brushed or brushless). It is also larger,
compared to a DC motor with a similar torque rating.
Figure 1 shows a size comparison between a stepper
and a DC geared motor. The one on the left is a bipolar
stepper motor (typically stronger than a unipolar), and the
by Dennis Clark
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re you thinking about Christmas and making your robot toys and tools list?
Maybe it's just me, but I work on that list all year long! I alternate
between having more toys than time, and just wanting more toys. There is
not enough time to play with everything that I want to play with!
Regardless, this has been a fantastic year for toys and new robot "things"
for Mr. Roboto. In the last couple of months, I have introduced you to a great new
IDE (integrated development environment) for Arduino and chipKIT projects. I also
discovered 4D Systems who has excellent graphics displays and design IDEs whose
costs rival other manufacturer’s LCD displays alone. Here is a whispered hint to those
of you that actually read my introductions ... I am going to be reviewing a couple of
fascinating new products from them in the next couple of months — as soon as I
build projects worthy of their "coolness" factor!
Enough rambling! I have a couple of questions to answer before I dash off to
MileHiCon's Critter Crunch this year. So, let’s get moving!