Ultimate 250-size mini-quad build (2 years of work)

In this post I will summarize all of my 250mm quad copter builds, and share what I have learned in the process. I have been meaning to publish this for quite some time, but, due to the long nature of the post, never got around to properly finishing it. Rather than letting it sit in my drafts indefinitely, I thought I would post what I have (mostly images) with the hope that I will find time to update it in the future. As such, this post is under development, with many details still missing. Feel free to contact me directly if you have a question that isn’t answered here.

I built my first mini quad after seeing my friend, Adam Polak’s, 250mm mini quad. He started with 3D printed 250mm frames and had just finished developing a cast polyurethane resin version. He had several prototype frames that he gave me to test. The first build in this post is using one of his prototype frames.

Polyurethane frame parts list:

1 x Frame
4 x SunnySky 2300KV motors
4 x Afro 12A ESCs
1 x ImmersionRC Video Transmitter
1 x SpiroNET antenna
1 x 600tvl sony camera
1 x D4R-II receiver
1 x MinimOSD
1 x Naze32 (original board)
1 x 1800mAh 3S Lipo
1 x FrSky DR4-II receiver (for use with my Taranis)
1 x HQ 6″ props
1 x Scorpion battery strap
1 x GPS





Later with T-Motors. They were worse than the SunnySkys.20140711_174647

After struggling to get the previous quad to fly well (there was a disaster with the SunnySky motors. My entire batch had magnets that fell out), I decided to go for a more standard bus-configuration quad frame. I preordered the Nemesis frame because I liked the idea of having a clean plate (which later turned out to be terrible).


My next build was based on the Nemesis carbon fiber frame, which I preordered. The main reason I was interested in the frame was the fact that it had “dirty” and “clean” plates, separated by rubber dampers. The ideas is that you mount your vibration sensitive components (camera and flight controller) on the “clean” plate, while the motors are attached to the “dirty” plate. It sounds great in theory, but turned out to be terrible. First, the rubber dampers were apt to break in a crash. As they are quite expensive, this alone was enough for me to stop using the frame. Second, I started to get pretty serious “wobble” on the upper plate as the rubber dampers wore out and became more compliant. I would occasionally hit some sort of resonant frequency coming out of maneuvers which would cause the wobble to become quite severe until I changed the speed of the motors. In any case, I eventually moved on to a better (and significantly less expensive) frame. The parts I used for the Nemesis build were recycled from the previous quad.

Nemesis carbon fiber frame parts list:

1 x Nemesis carbon fiber frame
4 x SunnySky 2300KV motors
4 x Afro 12A ESCs
1 x ImmersionRC Video Transmitter
1 x SpiroNET antenna
1 x 600tvl sony camera
1 x D4R-II receiver
1 x MinimOSD
1 x Naze32 (original board)
1 x 1800mAh 3S Lipo
1 x FrSky DR4-II receiver (for use with my Taranis)
1 x HQ 6″ props
1 x Scorpion battery strap
1 x GPS


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Finally, after my first two 250mm builds turning out pretty badly, I switched the a ZMR250 frame with a separate, power distribution board, which managed most of the power and signal connections for the quad. I also switched from 12A ESCs to my trusty old 20A ESCs, as I had had a lot of problems with the 12A afros burning out. Besides these two modifications, the rest of the parts were again recycled from the previous build (however, I started using different props and experimented with various cameras).

Nucleus PDB frame parts list:

4 x SunnySky 2300KV motors
4 x Afro 12A ESCs
1 x ImmersionRC Video Transmitter
1 x SpiroNET antenna
1 x 600tvl sony camera
1 x D4R-II receiver
1 x MinimOSD
1 x Naze32 (original board)
1 x 1800mAh 3S Lipo
1 x FrSky DR4-II receiver (for use with my Taranis)
1 x HQ 6″ props
1 x Scorpion battery strap
1 x GPS

This build turned out to be excellent. The ZMR250 frame was simple, and extremely durable. I had several crashes where I thought that the entire quad would be totaled, only to find that it was completely unharmed (I just flipped it over and took off). The only thing I had to replace frequently were the props. The power distribution board (PDB) was excellent, and made the build super clean. No wires hanging around to get caught in propellors, and an integrated power supply and beeper, which were great. The PDB also had white LEDs in the front and red LEDs in the back, which were very bright, and really nice at night. The only negative thing I will say about the frame is that the vibration-isolated camera mount is useless. Not only does it pop off (with your camera) in even the most minor crashes, but it introduces horrible wobble to the upper plate/camera. However, I found that strapping the camera (Mobius) directly to the top of the quad worked pretty well, with only minor jello from motor vibrations at certain throttle levels. I flew this quad for quite some time before selling all of my equipment.

IMG_0524 IMG_0525 IMG_0532

Almost no wires!IMG_0535 IMG_0536 IMG_0537 IMG_0539

Routing the antenna using zip-ties and shrink-wrap.IMG_0556 I took the DR4-II receiver and removed the cardboard package. Then I coated the board in liquid electrical tape. Then, just to be extra safe, I put shrink wrap around the board (mostly to make sure the antenna didn’t disconnect from the board. IMG_0557



Tricopter build (based on David Windestål’s design)

Having had my fill of quadcopters after my last crash, I decided to build a tricopter using my three remaining motors (one was damaged in the crash). David Windestål of FliteTest has a simple and sturdy design (see his build video) that I followed to build mine. As such, I will only be posting information that is unique to my build.

The tricopter has been by far the most exciting multirotor I’ve built. Because of its ability to use thrust vectoring in the yaw axis (unlike other multirotors which rely on torque vectoring) the yaw authority is extremely high, allowing for quick and precise rotation. Also, following David Windestål’s method of using zip-ties to attach everything has saved me multiple times in crashes, allowing the components to break off without being seriously damaged. Once you go tri, you never go back!

The unique aspect of my tricopter is the light and siren system. I wanted something that I could fly at night and looked like a police vehicle. So I added red, white and blue LED strips, as well as a 102dB siren, and built a custom, Arduino controlled, driver circuit to power everything.

Parts for the tricopter (that differ from David Windestål’s design):

1 x OpenPilot CC3D (Flight Controller)

3 x Tiger Motor MT-2216-11 900kv

1 x Turnigy 380MAX Micro Servo (Metal Gear) (This servo has given me some trouble, but is acceptable given its low price. Make sure you buy extras)

4 x Graupner E-Props 9×5 (R and L) (These props have proven themselves on previous builds and are fantastic on the tricopter. No other props I’ve tried have been close to as good as Graupners)

Besides the above parts, all other components are either the same as used by David Windestål, or were recycled from my last quadcopter build (i.e. ESCs, receiver, etc.)

Parts for light and siren system:

1 x ProtoBoard (these are common and can be found at your local electronics store (RadioShack, ect.).

1 x Red LED strip (1 meter) (12v)

1 x White LED strip (1 meter) (12v)

1 x Blue LED strip (1 meter) (12v)

1 x 102dB Siren

1 x 12v linear regulator (again, these are common and can be found at any electronics store). Because I’m running a 4S battery (16.8v) I have to step the voltage down to 12v for the lights. This is unnecessary if you’re running a 3S battery (12.6v)

4 x MOSETs (can be found at most electronics stores). MOSFETs are solid state switches (like relays, but much smaller and lighter)

1 x Arduino Nano (The Nano is connect to spare channels on the receiver and controls the lights and siren via the MOSFETs)

1 x Various other hardware (male and female headers, wires, etc.)


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DJI F450 Quadcopter Build

Bill of materials:

1 x DJI Flamewheel F450 Frame

4 x Tiger Motor MT-2216-11 900kv

4 x Hobby King 20A ESC 3A UBEC

4 x Graupner E-Props 9×5 (R and L)

2 x PolyMax 3.5mm Gold Connectors 10 PAIRS (20PC)

1 x Nylon XT60 Connectors Male/Female (5 pairs)

3 x Turnigy nano-tech 2200mah 4S 45~90C Lipo

1  x MultiWii CRIUS SE flight controller (not recommended)


Frame parts.2013-02-22 09.53.33

First solder the XT60 to the built-in power distribution board.
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Prepare the ESCs by soldering the gold bullet connectors to the motor leads and installing heat shrink around the ends of the leads. Next I cut the protective heat shrink off the the ESCs and flashed them with SimonK’s custom firmware (see the RCGroups thread for more info) via an AVR programmer and a custom made adaptor. I then put the ESCs back in transparent heat shrink.

Before modification.
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With the heat shrink removed, looking at the underside. Notice the six pads on the bottom right of the circuit board. These are the ISP pads.
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Next I made a custom adaptor that would align with the ISP pads on the ESC. The black socket is a 10P ISP header socket into which the AVR programmer is plugged.
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With the hardware prepared, I proceeded to flash the ESC via the command line method outlined here. Power the ESCs from a 9V battery (not a lipo) so that if there is a problem, you won’t do as much damage. I chose to have a motor attached so that I could hear the programming, calibration, and ready tones (not required). You will want to have a receiver plugged in (and your radio turned on with the throttle down) so that after flashing is complete you can calibrate your throttle range. Once all of this was set up I plugged my custom adaptor into the AVR programmer (which is plugged into the computer) and flashed SimonK’s firmware. AVR programmer and adaptor not shown.
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All four finished with transparent heat shrink.
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Next attach motors to arms, and attach the arms to the frame. Then trim the ESC’s input wires to the correct length and solder them to the power distribution board.2013-02-22 10.50.13 2013-02-22 11.23.12

With all the arms and ESCs attached
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Install flight controller, receiver, bluetooth telemetry module, foam battery rests, battery strap and the top plate of the frame.
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Complete with camera skids installed.
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Unfortunately, the MultiWii flight controller malfunctioned (for an unknown reason) on my first flight and the quadcopter ran into a wall at high speed, with the following result.
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Update to MultiWii 2.1

I recently updated the MultiWii code running on my quadrotor and computer to MultiWii version 2.1. It bosts several new features such as more GPS support. Unfortunately I am unable to take advantage of this because my GPS uses serial to communicate with the controller. This causes a problem because my CRIUS SE board only has one serial port meaning that I can run the GPS or Bluetooth module but not both at the same time. Although I am relatively confident in the MultiWii GPS code, I’m not comfortable running any autonomous routines without being able to test it first. Testing would require watching the configuration GUI to observe the motor outputs while moving the quad around by hand (with the props off for safety reasons), but while the GPS is attached I will not be able to use the Bluetooth module, thus cutting off my telemetry data.

As for flight performance I didn’t notice much difference. The quadrotor appears to be slightly more stable, although this could just be my imagination. The main improvement is in the configuration GUI. Here a screenshot:

Also, I discovered that there is an Android application that allows for tuning via Bluetooth. Here are some screenshots:

Conversion to quad (build)

I am currently in Denver, Colorado visiting my grandparents. Before I left Phoenix I received my cnchelicopter shipment, but did not receive my hobbyking shipment. This means that I will have all the parts for the conversion, except the USBasp AVR Programmer, meaning that I will not be able to set the board configuration to quad. However, I wanted to build the quad frame and make sure everything fit, and then convert it back to hex so that I could fly while in Denver.

The quad build:


Frame complete except for lower plate:

Speed controllers on:

Power distribution bundle installed and attached to speed controllers:

Motors installed:

Motor close up:

CRIUS SE, receiver and Bluetooth module installed:

Finished with feet:

The hex build (electronics installation same as quad and therefore not shown) :

Upper plate and arms:

Speed controllers installed:

Power distribution bundle installed and attached to speed controllers:

Bottom plate installed:

As mentioned above, the rest of the build is the same as the quad (motors, electronics, etc.)

Conversion to quadrotor (parts)

After having struggled to keep the vibration caused by two of the motors on the hexrotor down I decided to convert it to a quad, thus eliminating the two bad motors. Luckily the website that sells my hexrotor frame (www.cnchelicopter.com) also sells other frame configurations that use the same arms. This means that I am able to convert my hexrotor frame to a quadrotor frame simply by changing the center plates.
Because I was already paying for shipping I decided to pick up several other spare parts along with the body plates.
To complete the conversion I needed to reprogram my CRIUS SE. This was a problem as although I had an FTDI programmer, the FTDI power supply was shorted with the main rail (see First flight). This meant that I would have to reprogram the board via the ISP (in system programming) port. I found a USBasp AVR programmer for sale at www.hobbyking.com and, as with my other purchase, decided to order some additional parts along with it as the shipping was fixed.


My purchases from cnchelicopter:

XAircraft X450P Upper Plate

XAircraft X450P Lower Plate

XAircraft X450P Arms (one damaged a crash)

XAircraft X450P Feet

Xaircraft Hexa Upper Plate (cracked in a crash)

XAircraft X450P Motor Mounting Plate (one damaged in a crash)

XAircraft X450P Guide Ball Mounting Rod (current rod is not long enough to span the wider 90 degree angle of the quad arms)

Xaircraft Hexa Frame Electronics Mounting Plate (my current one has a GoPro mount attached to it that I can’t remove. Although designed for the hex frame, it fits on the quad and is larger than the quad version)


My purchases from hobbyking:

USBasp AVR Programmer

5 XT60 Female Connectors

4mm Banana plug to 6 x Male XT60 in parallel (because hobbyking was currently out of stock of their 5-piece bags of male XT60 connectors I decided to buy this adapter and cut the XT60s off)

Twin pack charge lead (2 x 3S)6S w/ XT60

Flat 26AWG servo wire 1mtr (R/B/W)

Turnigy Pure-Silicone Wire 14AWG (1mtr) RED

Turnigy Pure-Silicone Wire 14AWG (1mtr) BLACK

Turnigy 5mm Heat Shrink Tube – RED (1mtr)

Turnigy 5mm Heat Shrink Tube – BLACK (1mtr)