Building a cheap quad. Step 1: Mount the power distribution board (PDB) to the Reptile V550 (v2) frame

The Reptile V550 (v2) is a cheap frame, so it does not have any instructions. Luckily the PDB just fits enough the top frame after a few trial and error of using different screws and mounts. I used a M3 screw and a nut, I also eventually lowered it a bit later from this photo to accommodate the gimbal board.

Also pictured here is side by side comparison with my current DJI F450 arms. The cheaper one is not as white and narrower, it seems to be just as stiff though.

Starting to build a cheap but good quad copter

I decided to build a cheap but good quad copter.  My initial target is cost 1/2 or less of my current dji F450 with a E300 propulsion system.  And it must be just as good or better.

The 2nd quad will serve more as a FPV and UAV platform.  I ended up with the following parts:

• Reptile 550 v2 with 1 axis gimbal ($66). This is a TBS Discovery clone, which should be good for FPV and shares arms with F450, motors, esc for sharing spares. 
• Multistar 2212/920kv ($45). So I can share/use the DJI 9443 and 9450 props. I also like the easy off and on of the self locking props. I wanted a Sunnysky 2212/980kv but it seems I can't use the self locking props on it w/o the rare adapter. Another E300 set is too expensive, I can however move the E300 to it.
• Multistar 20A BLHeli ESC ($10 x 4).  Initially wanted a simonk based ESC such as the Afro.  I read there where a few issues especially for a Pixhawk flight controller.  So I opted for the BLHeli ESC.
• HK Pilot32 ($130). Always wanted a Pixhawk, I want to do some UAV and possibly coding but could not afford a 3D Robotics made one.
• Ublox Neo 7m GPS ($34)
• Minim OSD ($21). Will do more FPV, so I guess OSD is now a must.
• power distribution board ($4). Reptile V550 does not have a built in distribution board unlike a TBS Discovery.
• Nanotech apec g2 ($56)
• Walkera RX703a ($29). I have a walkera radio, as I share it flying the F450, Ladybird and Master CP.  The RX703a also use PPM signal which works for the Pilot32

Final adjustment and testing of gains for dji F450

Having added the FPV I needed to adjust the gains. Increased the pitch and roll a bit so it can handle the wind better. Lowered the Altitude pitch and roll as it seems to make it less jerky. Significantly increased the vertical, so it would not descend when moving.
Basic
150% Pitch 150% Roll 120% Yaw 200% Vertical
Altitude
110% Pitch 110% Roll

I tested the gains on a very windy condition in atti mode.

Final testing and adjustments. Wellington strong winds is the best place to give it a real world test. Not brave enough to go over water though, gust can really take the quad down as seen on one of the crash.

Wiring up some First Person View (FPV) video feed

Been busy for the past few weeks, today it was rainy.  So I finally got the shipped items to make my initial FPV.  It was pretty straight forward, some wiring and soldering.

I opted to get a basic 5.8ghz system for now.  This should be good for 500-1000m range with clear line of sight, from what I read.  Need to test/verify this on a good day.

I am still using a Mobius camera.  I got the Mobius video cable which goes from the USB port of the camera to the video transmitter (VTX).  The pins of the Mobius video cable is a direct match for the Boscam TS351.  No soldering required, just don't use the Boscam cable and directly fit the mobius video cable (yellow-black).

To power the VTX I opted to use my main battery.  I currently use a 3S LIPO battery, so I did not need to step down the voltage.  I only used a Fat Shark power filter.  Take note its important to reverse the wire polarity of the Fat Shark power cable, as the Boscam positive and negative terminals are the other way around of the Fat Shark.  I then just cut and soldered a splitter on the balance cable of the 3S battery.

My ground station video receiver (VRX) is still very basic.  I just opted to get a 7" monitor, will just get some goggles sometime in the future.  Some soldering and wiring was done.  I made a simple JST plug to 2.1mm adapter for the power.  Got some RCA male to male adapters.  Also made a simple JST splitter.  The 500mah 3S Lipo seems to last for about 45 mins or more, enough for my current flight times.

Perhaps the more fun project is fitting the Ladybird with a 808 #16 keychain camera.  The 808 is a 720p HD camera.  The little bug seems to fly with this heavy payload for a good 3 mins, using only the stock 280mah battery.  I got some 360mah battery coming.  This little bug will really give some good fun for my daughter.

Some tweaking of the quad after some flights

I have updated my settings after a few flights.

Cut the extended legs a bit, as the stock dji extended legs are too tall and bouncy.  Even the RTH can't land the quad without it falling over.

I have also change my gains to make it less wobble.  Current gains are:

Basic
145% Pitch 145% Roll 140% Yaw 120% Vertical
Altitude
140% Pitch 145% Roll

I have also mapped the IOC to X2 using the FMOD switch.

Naza Lite	Walkera Devo RX1002	Walkera Devo 10
A	AILE	Aileron (reverse)
E	ELEV	Elevator
T	THRO	Throttle
R	RUDD	Rudder (reverse)
U	AUX1	Flap/Mix (trim U 84.5% D 84.5% subtrim U 5.5%)
X1	AUX4	Aux4
X2	AUX2	Fmod (reverse trim U 90% D 90%)

Also changed the failsafe voltage to be higher on first level:

first level 10.6v 0.20v 10.40v
second level 10.20v 0.20v 10.00v

Some flights of it:

Done the finishing touches, quad is ready to fly

I have setup the Flight Controller FC, Radio Control RC, mount a Mobius action camera and legs.  Got all the functionality mapped on the FC.  It should switch to different flight modes, GPS, Altitude hold and manual.  I setup the failsafe switch so it would go back to its take off point when it looses radio signal or on flip of a failsafe switch.

Unfortunately I can't fly it over the weekend, there is bad storm.  Its very gusty and raining hard.

Here are some details of my initial setup:

Wiring between FC and RX

Naza Lite	Walkera Devo RX1002
A	AILE
E	ELEV
T	THRO
R	RUDD
U	AUX1
X1	AUX4
X2	AUX5

Naza Lite Assistant Settings and DEVO 10 settings to make them work

DEVO 10 is setup in airplane mode

Basic / GPS Mount
X -2cm
Y -4cm
Z 12cm
Also my GPS puck on the quad is rotated about 10 degrees towards the right.  This is to compensate for the magnetic declination.  See manual on Toilet Bowl Effect.

Basic / RC - I have used the default settings on DEVO 10 where all channels are normal.  I then setup the NAZA with the following:
A - Reverse
E - Normal
T - Normal
R - Reverse

The flight modes is controlled by the Mix switch (labeled as Flap on airplane mode).  For the U channel to set on the correct areas (GPS, Atti, and Manual)  I have set following on the DEVO 10

Trim / Flap U 84.5% D 84.5%
Sub Trim / Flap U 5.5%

I then used the Gear switch, to move U channel into the fail safe zone.  I used a program mix to achieve this.
Program Mix 1

master: Gear
slave: Flap
Pos 0(+) -50%

I have also the DEVO 10 failsafe to move the flaps should the radio loose signal

Failsafe flap U50%

I also set the "Fixed ID" binding, its needed so that when the radio signal is re-established you can take control again.  Otherwise you will need to power down the transmitter and receiver again to bind it.

For the gains I have used Aux4 and 5 knobs to adjust it.  Here are my initial parameters:

165 Pitch 165 Roll 150 Yaw 150 Vertical
Altitude 100 Pitch 100 Roll

Assign X1 and X2 to which one I wanted to adjust.  I then set the DEVO 10 trims and sub trim so the gain % difference is not big.

Aux4 Trim U40% D40% sub trim +7.0%
Aux5 Trim U40% D40% sub trim +12.0%

My initial failsafe voltage:

first level 10.5v 0.20v 10.30v
second level 10.20v 0.20v 10.00v

Wiring in the brain of the quad

Today just wire in the Flight Controller (FC) and receiver.  Hooked it up on the computer and transmitter for the initial setup.  So far things are connected properly

Finally tidy up the wires, mount the top deck and the GPS.

Next will be setting up the FC and GPS properly.