FIGURE 3.
The lightweight
3DR 900 MHz radio
telemetry system.
was the 3DR 900 MHz radio
telemetry system from DIY Drones
(see Figure 3). The $75 system is
sold as an XBee killer, with a smaller
footprint, lighter weight, and duplex
communications range of about one
mile. One unit plugs into the USB
socket of your laptop and the other
unit attaches — via cable — directly
to the board. It provides a virtual
USB connection between the board
and your PC with data rates of
about 250 kbps. The top unit in
Figure 3 plugs into the USB port on
a laptop, while the lower unit
attaches — via cable — to the
ArduPilot.
The Quadcopter Platform
FIGURE 4.
Close-up of
the power
distribution pads
for the Q450
fiberglass frame.
FIGURE 5.
Test mounting the
ArduPilot on the
lower plate of the
quadcopter platform.
The ArduPilot and Mission Planner
software are an amazing duo, but
they need a platform to show off their
capabilities. DIY Drones sells several
quadcopter frames, designed to carry
from three to six engines. However, in
the spirit of open source and DIY, I
opted for a Q450 fiberglass frame
with integrated PCB from HobbyKing.
The white and red frame was $18 and
about the same for shipping from
Hong Kong — still, a bargain at $36.
The Q450 was easy to set up and
wire, thanks to the integrated power
distribution pads on the PCB shown in
Figure 4. I attached a LiPo battery
using 4. 5 mm bullet connectors to the
pads on the lower left of the photo.
Similarly, I soldered the four pairs of
power leads to the ESCs using 3. 5
mm bullet connectors, then to the
four sets of pads at the base of each
arm. Total time: about 10 minutes.
In addition to the cost of the
frame, there were four 30A ESCs ($13
each), four 1,000 KV motors ($14
each), a set of propellers (two
clockwise and two counterclockwise;
$2 each), and four collets ($1 each) to
hold the propellers on the motor
shafts. I purchased everything from
HobbyKing. I also supplied several
4,400 mAh LiPo batteries, a smart
58 SERVO 11.2012
