wires and the soldered harness.
Photo 14 shows a close-up of the
main solder joint. Given the
significant heat and time involved,
solder must have wicked at least an
inch past the insulation on either
end of the joint.
Of course, all exposed 3. 5 mm
bullets either get covered in shrink
wrap or inserted into a connector
housing. I prefer shrink wrap for
space and weight savings. The
downside of shrink wrapping the
connection is that replacing or
repurposing the ESC requires
removing the shrink wrap.
Photo 15 shows the power
harness attached to the ESCs and
ready to accept the battery
connection (far left).
If I had to do it again, I'd
probably go with a commercial
power bus ($2-$4 at HobbyKing). It's worth doing once,
but creating a bus from scratch is a major time sink.
However, if you like packing your own chute, then build
your own. You never really know how much heat or solder
some worker (or robot) in China applied to a connector.
card in use.
Rotation Check and Rewiring of ESCs
( 20 minutes)
The quadcopter is able to maintain stability and
maneuverability in part because two of the rotors spin
clockwise and two spin counterclockwise. Looking down
on the quadcopter from above with the two red arms (in
my copter) facing away from you, the motors at 2 o'clock
and 8 o'clock should be configured to spin clockwise.
Configure the other two motors to spin counterclockwise.
Unfortunately, there is no universal color coding for
the polarity of motor leads. You'll have to check the
rotation of each motor and then — if a correction is
needed — switch two of the three ESC leads to reverse
the direction of rotation. Fortunately, a little servo/ESC
tester can verify proper rotation direction in
seconds. Simply plug in the ESC's PWM input
plug to the tester and 11.1 VDC to the power
Any servo tester will do, especially since you
just need to get the motor spinning for a
fraction of a second. I use the Turnigy Mega
Meter ($40, HobbyKing) which you should
consider. Alternatively, a dedicated servo tester
($10, TowerHobbies) will do. In a fix, an Arduino
set up with the standard servo library is another
option. However you manage to verify the motor
direction, secure the heat shrink on the ESC
connection when you're done.
Photo 12. Servo
extender with red
(+ 5 VDC) pin and
Photo 13. Power harness 12 gauge wires prepped
for soldering (top), and then soldered (bottom).
SERVO 09.2012 49