admirable job in many of these situations.
One drawback is their restrictive duty cycle of 10% or
six minutes an hour. Now, this may not sound like much
available time but you must consider the actual time that
the actuator is being used. With some careful thought and
creative programming, you can easily work with this
The installation may require more room than a
standard linear actuator which has the motor added next to
the shaft. The high speed actuator has the motor placed in
line, so plan your design carefully.
Could linear actuators or servos replace pneumatic
systems? It is possible if you do not have the ability to
incorporate an air driven system. However, I think they are
best when combined with pneumatics. There are many
instances where a linear actuator will outperform a
pneumatic cylinder and vice versa.
One such instance where I prefer to use a linear
actuator is if you need your mechanism to remain rock solid
in a particular place. By using an actuator, you avoid the
shock effect you get with pneumatics.
Since air is compressible, a pneumatic cylinder can have
a bit of a bounce.
Another application is in driving head movements. I
have never been a fan of using pneumatics for this task.
The action is too quick and I prefer my head movements to
be smoother, more subtle, and controlled.
Also, it is nice to avoid running stiff air lines up into the
head which leads to a neater installation.
In all fairness to pneumatics, actuators cannot exert as
much force, operate as quickly, or run continuously. If you
have the need for a large number of fast moving
mechanisms, it would be advantageous to make the initial
investment in a pneumatic system. You would then have
the option of using whichever design fits each individual
I am so pleased with the performance of the linear
actuators and servos I have been experimenting with that I
plan to retrofit a couple of my pneumatic props with them.
I have several props inside my house where I am unable to
run air lines. These require me to feed them air by utilizing
an 11 gallon air tank for each prop.
In order to extend their use to last the night, I am
forced to be very judicious in my programming, and strictly
control the number of times a prop activates.
By replacing the pneumatic cylinders with electric
actuators, I will no longer need to worry about the extra
equipment, and will not need to refill the tanks every day.
Now, they will be able to do their job whenever they are
The other system that I am often asked about is
hydraulics. They are similar, but are much more expensive
and overkill for the majority of our purposes. They also can
make a huge mess if they leak fluid (that’s another story!).
Perhaps, one day, I will hit the lottery and be able to
give them a try. Until then, I will leave those for the
professional prop builders.
Putting Things Into Action
I have shown several different options that you can use
to control actuators. They include DPST switches, wireless
relay remotes, and remote control transmitters. All reliable
choices, but they are surely not the only ones.
A handy tool that is always within arm’s reach on my
workbench is my four-channel servo recorder from
ServoCity. It is a handy way to test the motions of any servo
powered joints I create.
I can quickly add and record movements for up to four
servos, and then play them back without having to use a
microcontroller or do any programming. It is one more way
to save some time during the prototype phase of a build
(who doesn’t need more of that!).
It will also run your recorded program in a loop mode,
so it functions as a prop controller as well. Tools that can
perform multiple duties always have a place in my toolbox.
It came in very handy when working with all the linear
servos I have been playing with.
It is also possible to control your linear actuators or
servos from a microcontroller. An informative tutorial is
available from Firgelli Automations on using an Arduino to
manage them, and can be found at http://tinyurl.
I will be using my favorite PICAXE microcontrollers for
some of my projects, but choose whichever one you are
comfortable with. The argument over which microcontroller
is the best is not something I plan to engage in!
Time to Get Back to Building!
I hope you now feel qualified to integrate a few of
these into your designs. They can fulfill a multitude of
different tasks and are easy to operate. Even if you do not
have an immediate need for them, keep them in mind the
next time you are struggling to solve a design issue.
Once you factor in all the variables, you may find linear
actuators and/or servos are the perfect solution.
If you have any questions about this discussion or have
a project where you have used one, please share it with the
rest of the community on the forum. You can find it at
http:// tinyurl.com/hu6pxtz. The more we work
together, the better builders we will all become.
May the passion to build be with you! SV
58 SERVO 07.2016