14 SERVO 04.2017
Motors have their drawbacks and are often thought of for only the simplest movements. However, our designs may contain elements that are a perfect fit for the motion that can be provided by a motor. They may not be
suitable for your more complicated mechanisms, but can be
just the right answer for some of your secondary
movements. In fact, there may be instances where a motor
is better suited for the job than other options.
By being creative with your designs, motors can be
transformed from providing a simple movement into
something much more. Many motors are offered with
encoders to provide feedback to a controller, thereby
greatly increasing their functionality.
The fact that motors are easy to use doesn’t mean they
may not still be the best option. Do not fall into the trap
that just because you are an experienced builder that you
need to always use complicated or advanced techniques to
solve your design problems. Avoid the temptation to
overcomplicate a design.
Our goal should be to design a mechanism that will
accomplish our design goals in the simplest manner
possible. The less complicated a design, the less chance that
something will go wrong. If a design calls for a complicated
solution, then by all means, go that route. However, if
“simple” works, then simple it should be!
Important Considerations when
Choosing a Motor
AC vs. DC
One of the first decisions to be made is whether you
will be using motors that require AC or DC power to
The house outlets in the US are primarily wired for
120V AC, which provides an easily accessible source of
power. This choice may be appropriate for those starting
out as it simplifies the build process. However, the benefits
afforded by using DC power can outweigh this advantage.
Using DC power will introduce an additional consideration
into your design which may be worth the effort.
If your motor choice does require DC, you will need to
convert from AC to DC. This can easily be accomplished by
using a common wall wart. (We covered their use in depth
in the January 2017 issue.) I get many of my wall warts
from overseas, so there can be a substantial time delay in
getting them delivered. I do not want to hold up a project
while I wait for parts, so I try to keep a wide selection on
Most of the controllers we use as the brains of our
projects operate on DC power. Since we need to have DC
anyway, why not remain consistent and use it for our
motors as well?
By employing DC, we also have the opportunity to use
batteries as our power source. This gives us enormous
flexibility and allows us to break free of the tether we have
to a wall plug!
Although DC can still pose a risk, it is generally
accepted that it is safer than AC. If you are not comfortable
working with electricity, this may be the perfect chance to
include someone on your build team with the necessary
experience to safely handle this task.
By varying the voltage of our DC supply, we are able to
alter the performance of our motor. A couple of perfect
examples of how this is done can be found when we are
working with servos or wiper motors. You can — within
limits — adjust the voltage applied to increase torque or
adjust the speed of your motor. This gives you more options
and versatility when you are designing your mechanism,
which is always a good thing!
Try to minimize the number of different voltages you
use in order to reduce how many you need to stock. You
How many ways can we “turn the wheels” of our mechanisms? We have already
covered servos, wiper motors, pneumatics, and linear actuators in this series of articles.
This month, we are going to take an in-depth look at using some alternative motors in
Motors Make the World
Go Round By Steve Koci