24 SERVO 05.2016
Wiper motors can provide the solution to many build problems we face, and you would be wise to be familiar with them. They are inexpensive, can run on a variety of DC voltages (not just 12V), and will
provide high torque. They are easy to mount, can run
continuously (some come with a parking feature), and there
are several ways to control their speed.
There are a few drawbacks. They are heavy, require a
larger amperage power supply, and they rotate continuously
in one direction (lacks positional control) in their stock
configuration. We will address these concerns and look at
some options for dealing with them. We will also look at a
couple of exciting solutions to the positional issue which
will elevate the lowly wiper motor to top dog status! Its
performance will be nearly unrecognizable in comparison to
your typical model.
The Good, the Bad, and the No
Before we give it superhero powers, let’s take a look at
some of the useful features available to us on a stock wiper
motor. The reasonable price in relation to the benefits it
provides can certainly be a big factor. Used models are
available from junk yards, but their reliability can be
questionable. Even with a good Internet search, it can be a
challenge to figure out the wiring easily in order to get
them to run properly. Plus, you usually have to remove
them yourself so your cost in time must be considered.
Personally, I would rather spend my time building if given
the choice. They can be purchased for under $30 from
several vendors (see Resources).
One of the major benefits of these motors is the
capacity to provide high torque. Please be aware of this
when working with this power house. You do not want to
allow a finger to come between the armature and one of
the mounts. Unless, that is, you have no interest in using
that particular digit pain free while the break heals.
When we require high torque to solve a build
requirement, we usually turn to either pneumatics or linear
actuators. Both of these have issues which can make them
impractical for some builds. Wiper motors can provide an
alternative to these which may satisfy all your build
What can you do when your job requires high torque and the use of air is out of the
question? I usually reach for a wiper motor (Figure 1). What in the world is a wiper
motor? It is the same motor you use when clearing your windshield of rain. If this
option is new to you, please do not spontaneously run out and remove the motor from
your car and try it out. Worse yet, refrain from removing it from your significant other's
car! There are plenty of places where you can easily pick one up for a reasonable price.
By Steve Koci
Wiper Motors: Prop