PHOTO 8. Arms and
main chassis plates
installed. Forward is
toward the right, in
the direction of
both red arms.
the $10 for the card.
Once you've programmed the
ESCs, the next step is to prevent all
but one of three ESCs from supplying
power to the flight computer. The
HoverFly Open Board requires only
one + 5 VDC at 2A supply, and
multiple, parallel supplies can cause
problems — especially if one supply
generates a significantly higher or
lower voltage than the others.
You can remove the + 5 VDC
output pin from the three-pin
connector on all but one of the ESCs.
However, you risk permanently
damaging the ESC connector.
I prefer to add a 4" servo extender
cable to three of the ESC leads and
disrupt the power there. On either end
of each extender cable, remove the
power pin by carefully lifting the
plastic retaining tab and then pulling
out the wire and pin as in Photo 12.
Keep the wire intact so that you have
the option of using the extender cable
later in another configuration.
Power Distribution Bus
Fabrication (1.5 hours)
PHOTO 9. Close-up of arms
and main chassis plates.
Photo 10. ESC layout toward the
apex of each quadrant.
This is the "heavy lifting" part of
the build. It's a simple task — supply
power from the LiPo battery to each
of the ESCs. The challenge is making
the connection with minimum weight
We're talking about supplying 15+
amps to each of the ESCs at times.
Even at idle — without the motors
active — the ESCs draw 350 mA at
11.1 VDC. Obviously, there's no power
switch in this circuit. There's too much
I made a power harness from the
supplied 12 gauge wire, removing the
insulation from the middle of one wire
that connects the battery to one of
the ESCs. The remaining three power
wires attach to the main wire. I used
3. 5 mm female bullet connectors on
the ESC ends of the harness and a
single 4 mm bullet to match the
battery connector. Your battery may
require a different connector or a
different male/female mating
Photo 13 shows the starting
48 SERVO 09.2012