FIGURE 8. Bare 'X' frame of the AR Drone. The craft is facing left, as indicated by the
small nib just visible on the supporting brace.
For the price, the functionality
is amazing. Auto-land, auto-takeoff, and stationary hover are
lifesavers. The Wi-Fi control is crisp
and the video lag is imperceptible.
My only reservations are regarding
the noise and battery life.
This isn’t something you can
use to sneak up on a squirrel or
bird for a close-up. (Think Neato or
Roomba vacuum cleaner.) The
gears simply grind away. Battery
life is a mere seven minutes.
Moreover, the lithium-ion battery
requires 90 minutes to fully charge
on the stock dumb charger. Leave
the battery in for longer and risk
explosion. Extra batteries are $40.
There isn’t much you can do about
the sound level, but the battery
limitations are easily remedied.
i Tunes. The simulator (shown in Figure 9) is a good
approximation of the real thing, but is far from perfect.
Using the controller program, touch the ‘take off’
button and the AR Drone takes to the air and hovers in
place about three feet off the ground. Next, place your
thumb in the left circle and tilt your smartphone or tablet in
the direction you want the AR Drone to go. Increase or
decrease altitude or rotate the drone with your right
thumb. If all else fails, simply remove your thumbs from the
screen. The AR Drone will stop — dead in its tracks — and
hover. The other option is to hit the ‘emergency’ button
which causes the craft to dive towards the ground.
Assuming you fall in love with the AR Drone, your first
mod or at least next purchase should be more and different
batteries. The stock battery and charger are atrocious. The
battery is low density, has low current capacity, and the
charger will kill it if you don’t unplug the charger after 90
You could spend $40 for additional stock batteries, but
that would be a waste. I bought four 1,300 mAh/11.1V
40C Blue LiPo lithium-ion batteries from XHeli.com for less
than $50, including shipping. The Blue LiPo battery has the
same dimensions as the stock battery (see Figure 10) and
is a few grams lighter. There’s
nothing special about this brand;
just make certain the voltage and C
rating are adequate, and that the
size and weight are approximately
the same as the stock battery.
The standard battery is rated at
1,000 mAh/11.1V and only 10C
continuous discharge. The C rate is
the rate at which a battery is
discharged relative to its maximum
capacity. A 1C rate is equivalent to
discharging the entire battery
capacity in one hour; 10C means
that the stock battery can discharge
at a rate of 10 x 1,000 mA or 10A.
In contrast, the Blue LiPo’s
continuous discharge rating is 40 x
1,300 mA, or 52A.
FIGURE 9. AR Drone simulator
interface. After takeoff, place your
thumbs on the black buttons and
50 SERVO 08.2012