The hobby servo is an amazing device. The typical hobby servo is a collection of plastic or
metal gears driven by a DC motor, which is under the control of a specialized motor driver IC
and a feedback potentiometer. Back in the day, one would find hobby servos in most every
model airplane and model boat. If you really put a brain cell to it, radio-controlled model
planes, cars, and boats are actually specialized types of robots that depend greatly on the
controlled motion provided by a hobby servo. Hobby servos don’t care who drives them as
long as they are driven with a specifically
timed PWM signal. So, it’s not so strange
that the ubiquitous hobby servo has
rotated its way into today’s microcontroller-controlled robotic ramblers.
My first serious hobby servo controller was built
around an LM556 dual timer IC with a potentiometer
at the end of a joystick acting as the hobby servo
controller input. After discovering PIC microcontrollers,
my next generation of hobby servo controllers got a bit
more flexible as I could control the hobby servo PWM
signal — and thus the servo itself — with both firmware
36 SERVO 08.2008
PHOTO 1. This Xilinx CPLD development board
contains everything you need to put the XC2C64A
on the air. The idea is to put down and test
your XC2C64A design on this board before
building up the final hardware that will be
dedicated to your XC2C64A project.
PHOTO 2. This is the real McCoy. There are other
XC2C64A programming alternatives. However,
this CPLD and FPGA programming device is fully
supported by the Xilinx ISE WebPACK firmware
generation package. You can purchase this tool
from a number of electronics distributors.
