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FPV EPP Foam Combat Plane 28"

 
 

This build takes a 28" EPP foam plane and adds cameras and video transmitter for FPV flight and streamer-combat fun.  Features of this plane:
For the basic build of the plane, see my EPP Foam Combat Plane 28" article.

See the FPV parts list below for a list of the FPV-specific parts.

See here for a gallery of pics.

The weight (complete) without battery is about 320g.  (Not a lightweight flyer.  This plane is built for speed and agility, to be able to survive collisions, and to be easily repaired.)

Flight time with a 3S 850mAh battery is 4-6 minutes.

Notes:

Having the Betafight flight controller on board provides support for OSD, FrSky SBUS receiver, easy VTX frequency configuration, and stabilized flight modes.  The plane flies great in gyro-stabilized (acro) mode.  It took a bit of research and tweaking to come up with a good Betaflight configuration for airplane use (the Mixer.md doc is a good reference).

Using Matek F411-Wing Flight Controller:

(The original build used an F3 Omnibus flight controller; see below for the detailed write-up on that.)

The Matek F411-Wing flight controller can be loaded with Betaflight and configured for use with the plane.  (The Matek F411-WSE could also be used.)



See here for pinout information, here for a general wiring diagram, and here for a pic of my test rig.

The connections for motors and servos are as follows:

S1 <- Throttle
S3 <- Aileron
S4 <- Elevator
S5 <- Rudder
S6 <- Camera tilt [AUX2 (ch6)]
S7 <- AUX3 (ch7)

The resources are allocated as follows:

resource MOTOR 1 B04  # S1 <- Throttle
resource SERVO 1 B06  # S3 <- Aileron
resource SERVO 2 B07  # S4 <- Elevator
resource SERVO 3 B03  # S5 <- Rudder
resource SERVO 4 B10  # S6 <- Camera tilt [AUX2 (ch6)]
resource SERVO 5 A15  # S7 <- AUX3 (ch7)

# Rule    Servo    Source    Rate    Speed    Min    Max    Box
smix 0 2 0 100 0 0 100 0   # Servo 1 Aileron <- Stabilized roll
smix 1 3 1 100 0 0 100 0   # Servo 2 Elevator <- Stabilized pitch
smix 2 4 2 100 0 0 100 0   # Servo 3 Rudder <- Stabilized yaw
smix 3 5 9 100 0 0 100 0   # Servo 4 <- RC AUX2 (ch6)
smix 4 6 10 100 0 0 100 0  # Servo 5 <- RC AUX3 (ch7)

Any needed servo reversing should be done in the flight controller (not in the transmitter).  The servo-reversing commands look like this (use only the ones you need):

smix reverse 2 1 r   # reverse Servo 1 Aileron
smix reverse 3 0 r   # reverse Servo 2 Elevator
smix reverse 4 0 r   # reverse Servo 3 Rudder
smix reverse 5 2 r   # reverse Servo 4 RC AUX2 (ch6)
smix reverse 6 9 r   # reverse Servo 5 RC AUX3 (ch7)

See here for the basic Betaflight settings for the F411-Wing board.  See here for settings that include tuning and OSD values (and have "gyro_1_align_yaw = 1800" for configuring the board mounted with 180-degree rotation).  For the Matek F411-Wing the Betaflight board name is "MATEKF411".

Using F3 Omnibus Flight Controller:

See here for the basic Betaflight settings, which lay out on the F3 Omnibus board like this:



The resources are allocated as follows:

resource MOTOR 1 B08  # motor PWM1 <- Throttle

resource SERVO 1 A02  # motor PWM4 <- Elevator
resource SERVO 2 A03  # motor PWM3 <- Aileron
resource SERVO 3 B07  # motor PWM7 <- Aileron2
resource SERVO 4 B06  # motor PWM8 <- Rudder

resource SERVO 5 B04  # SBUS/PPM <- Camera tilt  [AUX2 (ch6)]
resource SERVO 6 A08  # ledstrip <- AUX3 (ch7)

# Rule    Servo    Source    Rate    Speed    Min    Max    Box
smix 0 2 1 100 0 0 100 0   # Servo 1 Elevator <- Stabilized pitch
smix 1 3 0 100 0 0 100 0   # Servo 2 Aileron <- Stabilized roll
smix 2 4 0 100 0 0 100 0   # Servo 3 Aileron2 <- Stabilized roll
smix 3 5 2 100 0 0 100 0   # Servo 4 Rudder <- Stabilized yaw
smix 4 6 9 100 0 0 100 0   # Servo 5 <- RC AUX2 (ch6)
smix 5 7 10 100 0 0 100 0  # Servo 6 <- RC AUX3 (ch7)

Because of internal-processor-timer constraints the PWM2 output cannot run a servo (only a motor).  Any needed servo reversing should be done in the flight controller (not in the transmitter).  The servo-reversing commands look like this:

smix reverse 2 1 r   # reverse Servo 1 Elevator
smix reverse 3 0 r   # reverse Servo 2 Aileron
smix reverse 4 0 r   # reverse Servo 3 Aileron2
smix reverse 5 2 r   # reverse Servo 4 Rudder
smix reverse 6 9 r   # reverse Servo 5 RC AUX2 (ch6)
smix reverse 7 10 r  # reverse Servo 6 RC AUX3 (ch7)

In my setup I needed to reverse the Elevator and Rudder servos.

I connected the flight battery to the VBAT pin on the flight controller.  The speed controller has a 5V BEC output, so with it and the servos connected to PWM pins, the 5V is supplied to the servos.

The flight-controller board is mounted with four M3x8mm Nylon Screws, going into four 5.6mm x 13mm M3 Nylon Threaded Spacers glued into the foam.  I also used four rubber grommets, but I don't think they really make much difference (in terms of stopping vibrations).

The video transmitter (VTX) is a TBS Unify Pro 5G8 HV (alt src), which supports SmartAudio for configuring the frequency and power output.  I powered the VTX directly off the flight battery, and supplied 5V for the cameras via the VTX.  The VTX SmartAudio configuration support requires a connection from the smart-audio pin of the TBS Unify VTX to the "TX" line of a UART on the flight controller.  (See here for info on SmartAudio.)

With the VTX setup for SmartAudio configuration, the video frequency can be configured using the on-screen video display and the R/C transmitter sticks; see the SmartAudio CMS OSD guide in the Betaflight wiki for more information.  The video frequency may be set using band/channel values, or to a frequency in MHz.  Starting with the v3.3 release of Betaflight, the video frequency may be configured using VTX CLI settings; see here for info.

I put the front-facing camera on a tilt servo -- I used a Power HD DSM-44 servo, but most any lightweight servo should work.  Adding a head tracker (like this one) lets you look up and down while flying, which I find helps a lot.  To switch between the front and rear-facing cameras I run them through a video switch controlled by an R/C channel from the transmitter.  I have it setup so the view will switch to the rear when I hit a toggle switch, or when I turn the head tracker enough to "look back."  I have the camera tilt on R/C channel 6 and the video switch on channel 7.

In this build I used an FrSky XSR receiver with its firmware updated to the F.Port Protocol Firmware.  (See here for an article on updating FrSky receiver firmware, and here for info on F.Port.)  The FrSky R-XSR receiver would also work here.

With a receiver connected via F.Port (or SmartPort), flight controller and VTX settings can be configured via 'lua' scripts on a Taranis / OpenTX transmitter.  (See here for 'lua' scripts and here for info article.)  I found that it's possible to set the VTX frequency while the flight controller is powered via the USB port and the VTX is not transmitting (because the battery is not connected) using the Taranis or the VTX CLI settings, and then have the frequency be applied when the copter is restarted.  (Be aware that after the change the VTX will transmit at the "old" frequency for a second or two while the flight controller is booting up.)

To get an RSSI (signal strength) indicator for the receiver, a configuration needs to be setup in the Taranis that routes RSSI to a RC channel.  The method in this article worked for getting RSSI directed to a channel, but the range of values was not right.  (The 'rssi_scale' setting in Betaflight v3.3 seems to have no effect for this type of setup.)  To fix the range I ended up directing the RSSI to a spare channel (CH26) and then to the channel that goes to the flight controller (CH16), applying weights and offsets along the way:
   * Taranis:  Input - create "rss" / RSSI input (weight=100)
   * Taranis:  Mixer CH26 with Source=(I)rss and Weight=500
   * Taranis:  Mixer CH16 with Source=CH26, Weight=360 and Offset=-85
   * Then set Betaflight RSSI Channel to AUX12 (CH16)
Also, to get it so the RSSI is displayed as 0% when the RC signal is lost, in the Betaflight Configurator Failsafe 'Channel Fallback Settings' do AUX12="Set 1000" (or set in CLI:  rxfail 15 s 1000).  With these things setup you can get a nice 0-100% RSSI displayed on the video OSD.

Here are the R/C channel assignments in my setup:

ch01: Throttle
ch02: Aileron
ch03: Elevator
ch04: Rudder
ch05: Arm Throttle
ch06: Camera Tilt
ch07: Camera Select (front/rear)
ch08: Flight Mode (acro, horizon, passthru)
ch09: Beeper
ch16: RSSI

I configured three flight modes, acro (gyro stabilized), horizon (self leveling), and pass-through, on a three-position switch (switch SD on my Taranis Q X7 transmitter).  In pass-through mode the R/C channels control the servos directly, and I configured expo in the transmitter for that mode only:  65% aileron, 65% elevator, 50% rudder.  No expo is needed for the other two flight modes.  Channel trim should not be applied in the transmitter, as it will adversely affect the self-leveling flight mode.

On my Taranis Q X7 I have the switches assigned as follows:  SA = Arm, SD = Flight Mode, SF = Beeper, SH = Camera Select, S2 (knob) = Camera Tilt

For the self-leveling flight mode to work well, the plane should be in a somewhat pitch-up position when the accelerometer is calibrated in Betaflight.  The calibration can also be trimmed up in that direction.

If the flight controller has a barometer, it can be used to show altitude in the OSD.  Some open-cell foam should be attached over the barometer chip to block sunlight and wind.  There is an altitude hold ("Baro") mode in Betaflight, but it doesn't seem to be implemented for airplane.

For tuning I needed to lower most of the values to tame oscillations, and I increased the servo 'rate' values to increase the responsiveness of the controls.

See here for a flight-controller configuration I've been using (in the settings directory).

See here for my Taranis Q X7 transmitter-settings file that includes this model ("EPPCom28").

A Bluetooth HC-06 module can be connected to UART2 on the flight controller to provide a handy wireless connection to a PC (running the Betaflight configurator).  In the configurator, the UART should have "MSP" selected.  The HC-06 module needs to be configured to a 115200 baud rate; see here for some more bluetooth information.

Alternate motor:  Turnigy D2822/14 Brushless Outrunner 1450kv
https://hobbyking.com/en_us/d2822-14-brushless-outrunner-1450kv.html

FPV Parts List:

Flip 32 - F3 - Omnibus v3 (w/ Baro option) $20.99
http://www.readytoflyquads.com/flip-32-f3-omnibus
https://www.banggood.com/Original-Airbot-Omnibus-F3-Pro-V2...1320254.html

FrSky XSR 2.4GHz 16CH ACCST Super Mini Receiver $19.99
https://www.getfpv.com/frsky-xsr-2-4ghz-16ch-accst-receiver-w-s-bus-cppm.html

TBS Unify Pro 5G8 HV - Race (SMA) Video Transmitter $29.95
https://www.getfpv.com/tbs-unify-pro-hv-5g8-race-sma.html
https://www.team-blacksheep.com/products/prod:unify_pro_hv_race

5.8GHz Circular Polarized Antenna RHCP (Short)
https://www.ebay.com/itm/254921978065

Power HD DSM-44 Digital Metal Gear Micro Servo $8.40
http://www.valuehobby.com/power-hd-dsm-44-digital-micro-servo.html

3 Channel Switch Module FPV Video Switcher $5.00 
https://www.ebay.com/itm/131631822928
https://www.getfpv.com/lumenier-3-way-video-switcher-board.html

5.6mm x 13mm M3 Nylon Threaded Spacer (10pc) $1.16
https://hobbyking.com/en_us/5-6mm-x-13mm-m3-nylon-threaded-spacer-10pc.html

Nylon Screw Phillips Head M3x8mm (10pcs) $0.86
https://hobbyking.com/en_us/nylon-screw-phillips-head-m3x8mm-10pcs.html

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