Here's a little tricopter I've made; the frame is EPP foam reinforced
with carbon-fiber strips. This little guy flies nice and is quite
cheap to built. Lot's of fun, whether flying it line-of-sight or
FPV.
See here for a PDF
of the design. It can be printed onto a standard
8.5"x11" letter-sized sheet. (When printing, set "Page Scaling"
to "None".) I attached the paper to a sheet of foam with
double-sided tape and simply cut along the lines to create the
frame. The carbo-fiber strips are glued (with CA) into the foam
for support. The three "legs" on the
bottom are 20mm x 20mm and 18mm tall, made
from two layers of the 9mm 1.9# EPP foam.
The motors, props, speed controllers and battery are the
same as what I used for my MiniFD. I like the HobbyKing 5030 props because they run quietly, but
they should be balanced and need to be reamed out a bit (using a 1.9mm
drill) before being pushed onto the motor shafts.
The motor to motor distance is 220mm (~9 inches); weight without
battery is 142g (5.0oz).
At first I was using a KK2.0 controller, loaded with KK2.0 v1.6++ Satellite firmware by RC911.
See here
for my settings. This setup worked well, except that the older
KK2.0 board has trouble with fast flips. (The current KK2.1+
boards don't have this problem.)
I'm now using an Acro Naze32 flight controller, running CleanFlight
firmware. See here and here
for settings I have been flying with. Setting "gimbal_flags=4"
(in the CLI) will result in RC channels 5-8 being output to the PWM5-8
pads. (With newer versions of Cleanflight this is accomplished
with "feature CHANNEL_FORWARDING".) I use the channel 6 output to
run the tilt servo on the FPV
camera.
The R/C control is via an OrangeRx R100 satellite receiver,
with the receiver's data line connected to the "USART2 RX" pin (4) on
the Naze32 and "feature RX_SERIAL" enabled. The R100 receiver
needs to powered with 3.3 volts (not 5 volts). There is a
3.3-volt pad ("3V") on the Naze32 board that can be tapped, or a ZYX-S DSM2 Satellite Receiver Cable can be used. The R100 has now been superceded by the OrangeRx R110X DSMX/DSM2 Satellite Receiver.
I found that any 'acc_lpf_factor' value greater than 0 resulted in a
self-leveling "lag" -- if I flew fast forward (in horizon mode), pulled
back to stop, and then centered the stick to level out, the copter
would keep "leaning" forward for a few seconds. Larger 'acc_lpf_factor'
values made it worse. My little copter flies well in horizon mode with
acc_lpf_factor=0.
I attached the flight controller to the frame with two layers of
4mm foam tape. The ESCs
are flashed with SimonK firmware (not one-shot).
The TS5823 video transmitter I'm using is rated at 7 volts minimum,
which isn't quite low enough for a 2S (7.4V) lipo-battery setup -- the
video would get messy toward the end of a flight/battery. A
Pololu 9V Step-Up/Step-Down Voltage Regulator (S10V3F9)
keeps the voltage level stable. I'm also using a video power filter circuit. Transmitter antenna is a HobbyKing Circular Polarized Antenna (RHCP) modified to have a right-angle RP-SMA connector.
I have a diversity setup with two separate Uno5800 receivers. I
do it with wired RSSI connections, but it could also be done with an Eagle Eyes FPV Station. The nice thing about
separate receivers is they can be placed far apart -- having one on
each side of a house can provide good signal all around.
