X155 Quadcopter Build with Omnibus F4 Pro V2 … by David HK February 2017
X155 Quadcopter Build with Omnibus F4 Pro V2 … by David HK February 2017
This is my 1st complete build from scratch of a brushless
quad. Before this I’ve replaced the AIO
FC+ESC board and motors of the Emax Nighthawk 280 Pro, and also built 2 brushed
micro.
The objectives of this build are to use the smallest frame that can fit
4” props, and be able to fit 1806 as well as 2204 motors, able to run 4S in the
future (motors may need to upgrade), light weight, X frame and unibody (less
screws to loose and easier to assembly and repair), and has side protection for
the camera, in the end I found what I want.
Below are my X155 components:
Frame: HK-X4 RS, size 155mm, I bought it from Taobao for around
US$15, able to fit 4” props (with a few mm spare), the one piece unibody with
arms is 3mm thick, has holes that can fit 1806 & 2204 motors, and there is
a top pod housing for the fpv cam and vtx.
Bare frame weight is just below 59g.
The design has some similarity to the Gearbest’s GEPRC GB190 but in a
smaller scale.
FC: Omnibus F4 Pro AIO, this is the v2 / pro version, with the blackbox
SD card reader onboard, built-in current senor and OSD. Since this is a new
build, so I decided to go to F4 (I was using Naze32 F1) for longer future proof,
and I like the idea of built-in OSD supported by betaflight and current
sensor. Previously I used the HobbyKing
Super Simple OSD. Running DShot-600 and
8K/8K gyro/loop.
PDB: since this is a small size build, so I use the Matek micro
pdb, supports 2S-6S.
Motors: SkyRC X1806 2300kv, 2S-3S. A regretted buy! An unheard of motor band, SkyRC makes lipo
chargers. I bought this set together
with another set of X2204 during a flash sale last year from Gearbest, at
around US$17 per a set of 4, and the close-up photos of the motors shown high
quality cutting and assembling, so I gave it a try. Per my bench test, the X1806 has around 270g
of thrust using KK4040x3 props and 3S lipo, a little bit under power, motor
weight is 18g, but at such a cheap price, considering them as learning motors.
ESC: Racerstar MS 25A BLHeLi_S from Banggood (yes, it is an
overkill for these low power motors, I originally bought these 25A ESC for my
bigger 280 6” quad, but then decided 30A is more suited for the bigger quad),
it supports DShot, I flashed it to BLHeli 16.6 with A-H-20 firmware and set it
up to DShot600 in BF without removing any capacitor.
RX: Frsky D4R-ii (since I am using the DJT module on the 9XRPro)
VTX: the mini TS5823 from banggood (note that this one has no output
power for the Cam)
FPV Cam: Foxeer HS1177 (I am running 5V from the pdb, less heat)
So here are the components in picture.
Below is my wiring diagram, in order to have current monitoring, the
Lipo power needs to go through the FC first, then to the mini pdb. The F4 FC powers itself directly from the
Lipo as it has its own 5V BEC built-in.
I did not use any power out from the FC for vtx and cam, as I have a pdb
that can provide regulated 12V and 5V. I
think pdb is designed to do this kind of jobs, not the FC, and it is a more
clean build in my opinion. If anything
fried, the pdb is much cheaper to replace.
I also saw in the rcgroups that there are quite a bit of confusion when
getting regulated power from the FC for vtx/cam, as it is either 5V or Vcc,
possible heat problem, etc. so one word:
“messy”!
For the video in / out of the FC to get the OSD display, both video signal
wires need to accompany by the ground wires of the components, as shown in my
wiring diagram. For the vtx is simple,
as it has separate ground wires for power and video. For the camera, I need an extra ground wire,
in my case, I routed it from the cam-ground -> pdb-ground -> FC vin-ground. I don’t want to join little Y shape wires as
these are too easily to break or loose after a few times of maintenance repair,
which is going to be needed as we fly and crash.
Frsky D4R-ii telemetry:
There is no dedicated telemetry pin for Frsky in this FC board, after a
lot of searching and special request, teralift has uploaded a pre-release BF
3.1.6 for OMNIBUSF4SD which can remap PWM5 & 6 to support softserial tx/rx:
For D4R-ii, I only need 1 wire for tx, so I connect the D4R-ii
telemetry green wire to PWM5 signal pin, and then in CLI type:
resource motor 5 none
resource serial_tx 11 a1
save
where 11 is softserial-1, a1 is PWM5 pin. Then turn on the Softserial and Telemetry FEATURE in BF GUI, then in the Ports tab, select frsky under telemetry column and set the baud rate to 19200. Remember to set the tlm_inversion = ON in CLI (default is ON).
resource motor 5 none
resource serial_tx 11 a1
save
where 11 is softserial-1, a1 is PWM5 pin. Then turn on the Softserial and Telemetry FEATURE in BF GUI, then in the Ports tab, select frsky under telemetry column and set the baud rate to 19200. Remember to set the tlm_inversion = ON in CLI (default is ON).
With the above done, I can get the voltage telemetry in my radio.
I added a few extra features in my wiring,
- a. An LC filter before vtx 12V power input. I have been using LC filter in my bigger quad and is a very useful item to have for a much clearer fpv view, worth the extra 7-8g.
- b. A Capacitor (35V, 1000uf) added to the Vcc pins in the pdb, this acts as a buffer zone to reduce redirected current noise caused by ESC motor dampen, improve fpv view and may avoid frying of some components when flying 4S in the future.
- c. Added a buzzer to the J2 pins
- d. Added a 12V single LED that flashes in different colours all the time to the front of the quad, using the pdb 12v output.
Below are still under investigation, not implemented, or can be
improved:
- a. The LED strip in J1, I tried just connecting a simple single colour LED in the J1 5v+ and ground pins, no power is detected. I already turned on the LED Strip feature in BF. Also the LED strip signal pin needs to remap to PWM6 in this FC etc. I am not that fancy in programmable LED strip, all I want is some simple single LED in front or back of my quad.
I soldered the ESC to pdb first, without realizing how short the quad
arms is, ending with the ESC almost touching the motors and not enough room to cut
the motor wires and solder to the ESC, so in the end I decided to fold the
motors wires uncut and placed them under the ESC.
Done! Flashed to BF 3.1.6. AUW without battery is 294g, a bit heavier
than I expected, I was expecting around 250g.
PID:
As I am still new to this quadcopter hobby, don’t know how to turn PIDs
yet. With the betaflight default PIDs, I
can fly smoothly, but a bit softy. I
came across the below PIDs from a diatone 150 in utube, since it is of similar
size, and I have the F4 and DShot-600 advantage, so give it a try. Turned out better than the BF default, more
agile and feels more powerful. Lately I changed both the pitch & roll “I”
from 32 to 34, this seems to reduce the wobbling when pushing the throttle a
lot.
set p_pitch = 48
set i_pitch = 34
set d_pitch = 25
set p_roll = 48
set i_roll = 34
set d_roll = 25
the yaw is BF defaults:
set p_yaw = 70
set i_yaw = 45
set d_yaw = 20Maiden flight video...
https://www.youtube.com/watch?v=XefbfDAsQTA
fast flying through trees video...
https://www.youtube.com/watch?v=OVE7Q1iBpS0&t=1s
Thanks for a very detailed build, was having issues trying to understand how to wire the battery input through the FC and then back to the PDB
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