Page 213 - Build Your Own Quadcopter_ Power Up Your Designs with the Parallax Elev-8

192 Bu il d Y o ur O w n Q u a d c o p t e r

Summary

I began this chapter by discussing what is inside a standard analog servo motor and how
those innards function. This was followed by a comprehensive circuit analysis of the servo
electronic-control board that receives an incoming pulse train and converts it to the
equivalent actuator motion.
In a discussion of the digital servo, I pointed out that there was little to no difference
between the analog and digital mechanical components. The main difference lies within the
electronic-control boards. The digital version provides significantly more torque, and it is
much faster at matching the changes in the incoming pulse train than its analog counterpart
is.
I next showed you how a continuous rotation (CR) servo functions and also how to
convert a standard analog unit into a CR unit. CR servos change motor speed and direction
in response to the standard servo pulse train, which is very handy if you need a low torque
and a low- to medium-speed motor. Otherwise, it is best to stick with a conventional motor
that has a complimentary speed control unit attached to it.
Next I discussed a portable servo-signal analysis system that could display on a 4 × 20
LCD screen the pulse widths for up to three R/C channels. The software, which was run
on a BOE, was thoroughly analyzed. I also included an in-depth discussion on the subject
of indirection and pointers, a sometimes bewildering topic, especially for beginner
programmers.
Then I covered two projects, the first of which was an LED-strip lighting controller. This
controller is designed to be placed onboard the Elev-8 and controls each LED strip based
upon the pulse width sent by the DX-8 Aux-1 (FLAP) channel. There are three separate
lighting modes, since the Aux-1 has three positions. This lighting controller enhances the
Elev-8 but does not affect its flight performance.
The second project was a tiltable platform that has a GoPro video camera attached to it.
The platform is mounted on the Elev-8’s bottom chassis plate and tilts to enable the camera
to view the ground while it is either hovering or in level flight. The platform is tilted by a
standard analog servo that is directly controlled by the DX-8 Aux-3 channel. The camera
platform may be continuously tilted from 0 to 90 degrees, since the Aux-3 control is a
potentiometer.
The next chapter will show you how to set up and operate an HD real-time video system
that uses the tiltable platform to increase the video coverage.