The leads of this
ducted fan were
soldered to the
short side of a
two-pin header.
I slid heat shrink
over the wires
after tinning
them, but before
soldering them.
Insert the pins
into a receptacle
before soldering
or heat shrinking
them. That
keeps the pins
in the proper
alignment while
they are getting
hot – and
possibly
softening their
plastic jacket.
I recommend color coding the wires in the circuit’s cable
system similar to what is illustrated here. The drive fan circuit
requires three jumper wires. Use cut resistor leads for the
jumpers. Be careful the transistors and diodes are not
soldered backwards.
the same (either both HIGH or both LOW), the voltage
across the fan output is the same so there is no voltage
difference to drive the fan’s motor. Setting the input pins
opposite to each other (one HIGH and the other LOW)
creates a voltage difference that appears across the fan
output and the fan motor spins either clockwise or counter-clockwise. There is no braking function in this H-bridge; the
ducted fans only slow down due to friction. I figure that’s
more like a rocket thruster anyway.
This is the schematic for one of the drive fan’s H-bridges
(this circuit is duplicated on the PCB for the other drive fan).
48 SERVO 11.2010
Put It All Together
Bolt all the HoverBot’s electronics, the lift fan circuit,
drive fan circuit, robot controller, and the battery packs to
the top deck. Do not bolt them to the bottom deck as it
breaks the airtight seal of the skirt and makes it difficult to
move the electronics around at a later time. Position the
electronics on the top deck so it distributes their weight as
evenly as possible. I also suggest placing as much stuff as
close to the center of the deck as possible.
I’ve experimented with using lithium cells for power.
They’re much lighter than alkalines and as I understand it,
they are used in electric airplanes. However, I’m still not
convinced they can provide the high current the HoverBot’s
fans need. So, use battery packs for power and you can
swap out the battery types to determine for yourself which
battery chemistry works best.
I use the same subroutines to drive and turn the
HoverBot that I use to drive and turn a wheeled robot. The
subroutine to drive a ducted fan forward looks like this:
Forwards:
high 2
low 3
low 4
high 5
return
However, the code has to use reverse thrusters every
