incredible torque of 694 oz/in at
7.4V, and is one of the new D
series servos (Figure 6). This servo
offers some significant
improvements, including the ability
to accept a wide voltage range of
between 4.8V and 8.4V. It
incorporates steel gears and dual
ball bearings to go along with its high resolution.
Quality servos are available from a number of different
sellers including ServoCity, Pololu, SparkFun, RobotShop,
Parallax, and Adafruit. I have provided links to their sites in
the resources section.
Now, it is time to examine the benefits that moving
from analog to digital servos can provide you. Be warned
that once you try them, you may never go back!
The primary components of a digital servo are the
same as those in analog servos. Their magic comes from
how the signals are processed when providing power to
the servo. The advantages of choosing a digital servo over
an analog model include the fact that digital servos have
increased holding power, decreased deadband (neutral
zone), and are quicker to respond to input.
This is a result of the higher rate of command pulses it
receives, allowing it to update its position more frequently.
The flip side to this choice is that digital servos are
more expensive and consume more power than an analog
By adding a programmer to your toolbox, you can
unlock many of the user controlled options available when
using digital servos.
In order to fully utilize all the features of digital servos,
you will want to have a programmer. I just picked up the
new Hitec HFP- 30 which is compatible with all of their
digital servos including the new D series (Figure 7). It also
doubles as a universal tester (see Resources).
In addition to being a servo tester, the HFP- 30
programmer allows you to access and adjust a slew of
features. The ones I find most useful are the ability to
adjust the speed and the direction of the shaft’s rotation,
as well as the capability to select your end points.
You also can adjust the deadband width, the neutral
points, fail safes, and the resolution, as well as select
whether you want the overload protection enabled. The
large screen makes for ease of reading. The battery is
external, so make sure you have one with the necessary
Another option that may work for you is the DPC- 11
dongle PC programmer. This computer interface is
compatible with some of their servos, so check the specs
to see if it will work for you (Figure 8).
The ability to increase your servo’s performance is
possible by including them in a system that has the ability
to augment the available torque and increase the load
bearing capabilities. These objectives can be met by
SERVO 02.2017 33
Figure 7. A portable programmer that goes where
Figure 8. Programming from your
Figure 10. Channel
mount gearboxes for
Figure 9. Servo blocks provide a strong skeleton.