Chameleon Build

By ShutterPriority on Apr 02, 2017

4 747  7 

Combo racing/freestyle build, plenty of power, but not obsessing over Thrust:Weight ratios

Soft-Mounting of PDB/FC via Armattan 3m 9448A PDB Pads and O-rings
OSD via F4 Omnibus running BetaFlight
VTX control over SmartAudio via SoftSerial resource-mapped to PWM5
Pagoda Antenna from FarVew

DSHOT 300 at 8K/8K PID/Gyro rates - Smooth!

AUW - 541 Grams: Approx 8:1 Thrust-Weight Ratio

What I loved most about this build:

  • Armattan Frame fit/finish and PDB soft-mount.
  • Blackbox SD cards on FC
  • The way it flies afterwards...

What I loved least about this build:

  • Armattan PDB to Omnibus F4 ammeter/shut resistor wiring. I wanted to keep the Armattan "Connector Saver" rubber XT60 mount to the Soft-Mounted PDB, but also wanted amps used/drawn on the F4 Airbot Omnibus OSD. It looks a little hacked, but still does the job. (see photos)
  • Diatone SW402 Didn't like to be waterproofed. 3 LEDs died after conformal coating(!??) [MG Chemicals Acrylic #419C]
  • Documentation for Airbot Omnibus F4 Pro V3 is limited. Thank you RC Groups!
  • No solder-points for UART access on Omnibus F4 Pro V3, only JST headers.
  • PDB soft-mount + O-rings increases height of stack so that J10 JST header (for UARTs) on Omnibus F4 Pro is not usable - access blocked by aluminum camera mount rails

Note: Omnibus F4 Pro has issue with SD Card logging for BB logs: you must set sdcard_dma=OFF in order to use BB logging to SD or your quad will freak-out at some point in flight. This is not a BF issue, it appears to be an issue with the STM F4 DMA handling of concurrent R/W requests.

PID Filtering and Tuning Notes

Final PIDs for this build (P / I / D) on these props:

  • Roll 46 / 62 / 27
  • Pitch 55 / 75 / 30
  • Yaw 70 / 90

  • Set d_term_type filter type to PT1
  • Disabled Gyro Notch-1 and Notch-2 - nothing excessive seen in terms of spikes.
    These 2 things had the most impact on handling and propwash handling alone. It flys where you point it, and I have to turn hard into my own turbulence to get propwash now.
  • Had to leave D-Term Notch, and move it down to 186hz (cutoff 120hz) to match spike seen in BlackBox
  • Set Dterm_lpf_hz to 90 - low idle d_term oscillations seen at around 95hz @ low throttle on ground and when chopping throttle and 'falling' in-air during stunts. Would warm motors up very quickly.
  • Set Gyro_lpf_hz to 80 - to keep in-line with Dterm_lpf frequency offset.

Photos

Discussion

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Joshearl   Apr 04, 2017  

How did you accomplish having both current sensing and OSD along with the rubber connector saver?

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ShutterPriority   Apr 09, 2017 

I've gone back and forth on the wire gauge.... I'm bursting to 75Amps total draw when I run Racekraft 5051's so I'm not sure I'd want to go much smaller in terms of wire.

I did have the 14AWG ground wire pull out (break, due to use) the other day, so I replaced it with a 12AWG down to the PDB to hold it in better, and tried to keep my tinning to just the very tip.

No, the positive feeds need to be separated, they can't both run through the PDB hole, one needs to feed the shunt resistor, the other is the return that goes to the PDB, and those do need to be adequately beefy to pass the current.

Birchyman   2 days ago 

I am planning on having hte XT60 hard mounted into the PDB, adn running 14awg wire from the bottom of the pdb (where hte pos and neg of hte XT60 go into the holes) to power my FC - will this work? Your last statement above seems to suggest it wont.. but want to confirm.

Birchyman   4 days ago  

Del~

 Respond  
nickthenorse   15 days ago  

Can you take a picture of your rear LED board installation? How are you holding it in place? Thanks!

ShutterPriority   10 days ago 

LOL, high tech stuff -- 3M VHB double-sided adhesive tape. It's still the same set from the original pics, even though this build has quite a few flights (and a crash or two) on it, and still sticking to the aluminum/carbon. I'll try and take a pic.

EDIT - Added a pic to the end. Just two "half-strips" and a full strip layered up to make up the difference between the carbon and the aluminum bits.

nickthenorse   10 days ago 

Nice one! Thanks :)

gdecedue   15 days ago  

I see you got smartaudio to work .
My vtx got hot and melted when I get the replacement I have serial rx1 turned on and skipped a line and have the tbs smart audio as a choice is there some other thing I have to do to make it work?

ShutterPriority   10 days ago 

In Betaflight choose 'smartaudio v2' on that RX port, that's it. Once I got the softserial figured out for this board, it worked from there.

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