batteries are very susceptible to
permanent damage. Do any of the
following and you might as well take
your battery to the recycling center:
• Drain the battery below three
volts per cell.
You need a special charger to
charge Li-Po batteries. The one
shown in Figure 10 is very
inexpensive, and can discharge and
balance your batteries.
It is very important that each cell
in a Li-Po pack be at the same
voltage. If they aren't, draining a
multi-cell battery could result in one
of the cells dropping too far and
getting damaged. Each multi-cell Li-Po comes with a balancing connector
in addition to its normal connector.
The balancing connector is actually a
tap into each cell in the pack. This
allows the charger to look at the
individual voltages of each cell.
During a balance charge, the
battery is charged and then the
higher voltage cells are each
discharged until they reach the
lowest cell in the pack. You don't
have to do a balance charge each
time you charge, but it should be
done every couple charges.
If you treat them well, Li-Po
batteries will last a long time.
40 SERVO 11.2012
To run a quad, you can do it with
a four-channel radio, but this leaves
no room for expansion. For this
reason, the minimum I recommend
for controlling a quad is six channels.
All the radios shown in Figure 11
are 2. 4 GHz radios except for the one
in the upper left corner; it is an older
72 MHz Futaba six-channel helicopter
Hobby King HK6S
This radio is the least expensive
radio I own. I have used it to fly
multiple quads and to control various
robots. It feels cheap, because it is.
The auto centering controls never truly
return back to center, so it can be a
little difficult to fine-tune a quad. I
don't think I would trust an $800
quad to this radio.
The transmitter uses four AA
batteries. The receiver seems to be
better quality than the transmitter.
I purchased two of these radios
from a local hobby shop. These were
used to allow spectators to control
two battling robots at the DC
Science and Engineering Fair held