October 2015 17
while using a “throttle-type” device
to make the quadcopter climb and
descend (which is much like the
standard helicopter control devices).
Table 1 shows a very rough GPIO
map of this control method using
eight inputs and four outputs. The
Raspberry Pi can send a Pulse Width
Modulated (PWM) signal from
the its output port to operate the
brushless DC motors which turn
the quadcopter propellers either
clockwise (CW) or counterclockwise
(CCW).
The circuit shown in Figure 4
should work to control the copter’s
motors, with the component values
chosen based on the motor’s
characteristics (voltage, amp draw,
etc.). The Raspberry Pi offers
the capabilities of “tuning” the
Proportional, Integral, Derivative (PID)
controls which will make operation of
the copter (or any other device being
controlled) smoother. See the Q&A
answer on “Proportional Integral
Derivative (PID) Control” next for PID
basics.
(PID) Control
QCould you explain PID control?
APID control involves a lot of mathematics which take a setpoint (desired operating point) and a
measurement of the variable to be
QUESTIONS and ANSWERS
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www.nutsvolts.com/index.php?/magazine/article/october2015_QA.
n FIGURE 3
n TABLE 1
n FIGURE 2
n FIGURE 4
