Quadrotors are the new Segways: a mesmerizing, somewhat magical, self-stabilizing platform that every tech person wants to have. You can't ride a quadrotor (well, maybe you can), but they do fly, and you can build one yourself from scratch!

I helped with a previous quadrotor build (Instructable here), and after flying it I decided I wanted to make my own. I had an idea to make a miniature one comprising a single printed circuit board that is both its structural frame and its electronics motherboard. The end result was "4pcb", a 138-gram micro quadrotor. I designed it in EAGLE, soldered it, and tested it over the course of a few months. Here's some video of it flying, after a lot of control tuning (see Step 13) and practice:

More flight video in the final Step!

The idea of making a PCB-based quadrotor isn't unique (see links below for other examples), and 4pcb definitely isn't the smallest (see the Picopter Instructable for a really tiny one). But I think it strikes a good balance between size, cost, buildability, and flyability. It's also one of the only PCB quadrotors with integrated brushless motor drivers, so there's no need to wire up external ESCs. And it runs on XBee digital radios, so there's no RC receiver or servo-style wiring.

4pcb Specifications:
Size: 6.50" (165mm) motor center-to-center distance, diagonally
Battery: 3S (11.1V), 370mAh, 20-40C Lithium Polymer
Motors: HXM1400-2000 "hexTronik 5gram Brushless Outrunner 2000kv"
ESCs: Toshiba TB6588FG "3-Phase Full-Wave PWM Driver for Sensorless DC Motors"
Props: 4x2.5 (2), 4x2.5R (2)
Controller: Arduino Pro Mini 328 - 5V/16MHz
IMU: Pololu MinIMU-9
Radio: XBee Series 1
Total Weight: 138g
Additional Payload: <30g
Flight Time @138g: 8min

4pcb is a "low level" quadrotor build, by which I mean that there are very few black box components. The frame, motor control, flight control, radio interface, and ground station UI are all developed from component or sub-module level. Depending on your level of experience and interest, you may want to take a different approach where you buy commercial modules for some parts and DIY others. (I included links to some kits and modules below.) This Instructable includes all the files and information you would need to build one completely from scratch.

There are a few small changes I would make if I did a second version of the board, but overall, I think it could make a good standalone project or, even better, a great starting point for your own modifications! (6pcb hexrotor, anyone?) Here are some resources that you might find useful, whether you are building this particular quadrotor or a different multirotor:

Other Quadrotor Instructables:
quadrotor - Custom frame with Arduino-based controller.
RC Quadrotor Helicopter - Off-the-shelf frame with custom controller.
Picopter - A very tiny custom PCB quadrotor.

Multirotor Frame Kits:

Multirotor Controller Kits:
HobbyKing (based on KK Multicontroller)
OpenPilot CopterControl

Complete Solutions:
Parrot AR.Drone - Very stable iPhone-controlled quad.

General Multirotor Resources:
RCGroups Miniature Quadrotor Thread
DIY Drones Quadcopter Forum
OpenPilot Multirotor Forum
PID Tuning for Multirotor (OpenPilot TV)

Mini Quads (5" props)
TinyCopter (custom build)
BabyCopter (custom build)
Turnigy Integrated PCB Micro-Quad (KIT) (commercial)
Blade mQX (commercial)

Micro Quads (4" props):
4pcb (custom build)
Kawaiicopter (custom build)

Nano Quads (3" props):
Nanocopter (custom build)
Nano quadcopter wii (custom build)

Pico Quads (2" props):
Walkera QR Ladybird (commercial)
CrazyCopter (custom build)
Picopter (custom build)
Chibicopter (custom build)
NC-ONE (custom build)

My Pages:
4pcb and other Flying Things
The Balance Filter - Merging accelerometer and gyro signals.

Step 1: The Setup: Parts, Tools, Software, and Files

The attached file (4pcb_DOC.zip) contains all of the support files for making and flying 4pcb. Included in the zip file are:

4pcb_ARD (folder) - Arduino project (Arduino 0022, .pde).
4pcb_EAG (folder) - EAGLE board files and libraries (EAGLE 6.0.0 Light Edition).
4pcb_EXE (folder) - Ground station executable (requires .NET Framework 2.0 or later).
4pcb_GRB (folder) - Gerber files for PCB printing.
4pcb_VB (folder) - Ground station source (Visual Basic Express 2008 or later).
4pcb_BOM.xlsx - Bill of material in Excel format.
4pcb_DIR.jpg - Coordinate system of quadrotor and IMU.
4pcb_EXT.pdf - Details of external connections.
4pcb_IMU.jpg - Image showing vibration mounting and wiring of Pololu minIMU-9.
4pcb_SCH.pdf - PDF schematic of the board.

Bill of Materials / Cost:

The Bill of Materials (4pcb_BOM.xlsx) lists all the components required to put together one PCB quadrotor and ground station. The total cost to build the quadrotor is about $240. The ground station consists of a USB game controller, an XBee radio, and and XBee-to-USB adapter. If you don't already have these, they add an aditional $80 or so.


This board requires a good amount of surface-mount soldering, including passives as small as 0603 and four TSOP36 ICs. They can all be hand-soldered (no BGA or leadless).

Additional Tools and Hardware:

- Wire (22AWG and 28AWG stranded would work) and wire cutters/strippers.
- Solder braid for cleaning up bridges.
- FTDI cable for programming the Arduino Pro Mini.
- Hex key set.
- Double-sided foam mounting tape.


If you want to modify the printed circuit board, you'll need EAGLE v6.0.0 or later. You can download it here. The free "Light Edition" is sufficient, even though the outline of the board is larger than 100x80mm limit (see Step 2). You will also need EAGLE to reference the board layout when placing components. (e.g. Type "show R32" in the board window command line to figure out where to put resistor R32.) There are no designators on the board itself.

The flight controller is written in the Arduino IDE. You can download the latest version from here. Make sure you set the board type to "Arudino Pro Mini (5V/16MHz) w/ ATmega328".

-Visual Basic Express (Optional)
The ground station is programmed in Visual Basic Express. If you want to modify the ground station software, you can download the free edition, Visual Basic Express 2010 from here.

-.NET Framework
The ground station requires the .NET Framework runtime files. (Unfortunately, this makes it Windows-only.) These files come with Visual Basic 2010, so if you plan on modifying the ground station software, there's no need to download them separately. If you just want to run the ground station executable, you can download the .NET Framework runtime files from here.

-Processing? (Optional)
Although I haven't done so myself, it is possible to port the ground station software over to Processing, which would make it compatible with other operating systems. To read from the USB game controller, there is a third-party library called ProCONTROLL. I did some work with this for a XBee-based robot controller, the details of which are here. This could be a good starting point for making a non-Windows ground station.
<p>thank you .it was exellent</p>
<p>fantastic &lt;3 ^_^</p>
<p>It's a nice instructables!<br>I also want to build my own arduino-based quadcopter, but I have problems in controlling the motors.<br>Do you have your program saved somewhere, for example github or anything else? I really want to take a look at it for my reference, especially for implementing the PID Control<br>Thanks before!</p>
<p>Hi, your whitepaper link does not work. Do you have it saved elsewhere online? Would love to read it. Thanks!</p>
<p>I really enjoyed ;)</p>
<p>I really enjoyed. thankssssssss ;)</p>
<p>Great instructable. I have a quick question; in the schematic why did you use 0 ohm resistors and why are some components not meant to be placed( the parts you said DNP)? You could have excluded the parts you do not need.</p>
<p>Only Wow, this project is amazing! <br>(Frist sorry for my bad English) <br>I tried to adapt the code in my own quad to do it fly in x mode, but without success. The difference is that my IMU is turned 45 degrees compared to the project that there is here, the pitch of the IMU is at the center between the motors. This orientation of the IMU creates problems?<br>Thanks to the help and the patience. </p>
<p>found this blogspot by shane: http://scolton.blogspot.com/2011/08/something-like-flight.html. this particular blog about the control structure really helped me. the entire blog site, matter fact, is a gold mine of information. go check it out if you're also having trouble or would just like to see how amazing shane really is.</p>
<p>Would like to thank you man. Your balance filter theory helped us a lot get through our final undergraduate research last year. Worked better than any DCM or kalman filter code we ever wrote, probably because we understood your filter the most. I just got back to the hobby after a half-year lay-off, and just now remembered I should thank you for posting all these wonderful control information, without which I'm sure we would have all stayed grounded.</p>
mark !very cool
Great Instructable. I just have one question... In a video that was added its mentioned that activating the 12.5HZ low pass filter on the gyro really helped stability. After reading the datasheet on the gyro it says that there is a low pass filter but the sheet only gives instructions for controlling the High-Pass. Did you add a software filter or am I missing something on the datasheet?
It is a little unclear in the datasheet. Right above the High Pass settings, starting on p.29 of http://www.pololu.com/file/download/L3G4200D.pdf?file_id=0J491, there is a setting for &quot;DR and BW&quot; (data rate and bandwidth) which are the low-pass filter and output data rate settings. The lowest setting is 12.5Hz cut-off for the LPF. It's rather harsh, but it seemed to work better than 25Hz. If you could cut the vibration down a lot (by careful balancing of propellers and such), a higher frequency cutoff would be better.
how long this quadrotor can fly??
Flight time is about 8 minutes, depending on the size of the battery.
Hi, i think u did a great job. at least, i think it's a tall order for me. though i love href=&quot;http://www.rctophobby.com/rc-helicopters.html&quot;&gt;rc helicopters, i still knew <br>nothing about the details of the machine. however, after your presentation, i think i have a notice note about it. thanks for share it, good job!
Hi, i think u did a great job. at least, i think it's a tall order for me. though i love href=&quot;http://www.rctophobby.com/rc-helicopters.html&quot;&gt;rc helicopters, i still knew <br>nothing about the details of the machine. however, after your presentation, i think i have a notice note about it. thanks for share it, good job!
found this blogspot by shane: http://scolton.blogspot.com/2011/08/something-like-flight.html. this particular blog about the control structure really helped me. the entire blog site, matter fact, is a gold mine of information. go check it out if you're also having trouble or would just like to see how amazing shane really is. <br>
Hi shane. great work by the way. I've been trying to implement the same control structure in my own quad. My quad is way bigger than yours but I'm using the same IMU. My propellers are 10x4.5. I also use smaller ones which are 8x4.5 for testing. As such, I'm having a hard time determining what value to start my kp and kd constants at. I've been trying to tune for a month now and I haven't had a successful flight yet.
excellent project and videos. i saw a TED video of this a while back really wanted to do this. <br> <br>i am new to this so was wondering if there are any books/literature you would suggest to better how this particular system works as a whole and how each of its parts interact with each other? also, if one wanted the altitude feedback and return to horizontal position, would it be just as easy as rewriting some of the code for the Arduino board or would some extra hardware/electronics such as the gyros be required as well? Thanks!!
I don't know of any books in particular, but many of the links at the bottom of Step 1 have great information on the different components involved in multirotor systems. As written, the code already has &quot;return to horizontal&quot; capability (see Step 13), but if you wanted to add altitude hold, you would need some way of measuring absolute height, such as a barometer or ultrasonic distance sensor.
I'm surprised you got it so small and it could still carry its own battery. Nice work. <br>I'm working on a similar project with a much larger form factor (Turnigy Talon v1) and we're having massive trouble with vibration on our gyro. I have the picture of your foam mounting but I can't really tell how it's set up. Is the sensor board weighted and set on top of a foam loop, or is the gray foam wrapped around something? <br>Thanks.
The weighted IMU sat on top of the foam loop. <br> <br>I also have a Talon v1...it's a great frame. But yeah I haven't had much luck with mounting the controller or IMU directly to it. Some kind of isolation is needed.
In the schematic , Obviously where it says DNP is open circuit however where it lists the resistors as 0 is that meant to be a closed circuit. For example R18 is a direct connection from pin 15 to the 3 resistors but there is no cap to ground ?
Yes, all DNP and zero-ohm resistors are for configuring the various settings on the TB6588FG. They're either shorts or open-circuits. So you could use a solder bridge instead of an actual zero-ohm resistor.
I was about to ask if you were affiliated with MIT, then I noticed you were testing it in Building 7!
Congrats on the win! <br>You provide excellent specs on components. <br> <br>Bill
How did you choose your motors?
For this size quadrotor, there weren't many options. But in general, you would choose the motor and propeller at the same time. There are suggested propellers listed for most motors. Sometimes you can also find data on thrust/RPM/current values with different propellers. <br> <br>The total maximum thrust should be 2-3x greater than total weight, so that you have plenty of extra thrust available for maneuvering and stability. I think on this quad it was much closer to 1x when I was using the 7.4V battery. Switching to 11.1V made it closer to 2x, which improved the stability a lot.
Would this battery be a good choice for this quadrotor? <br> <br>http://www.hobbyking.com/hobbyking/store/__11895__Turnigy_nano_tech_370mah_3S_25_40C_Lipo_Pack.html
Yes, that's the exact one I used.
As of August, 2012, there is MinIMU-9 version 2. Did you use the version 1 or 2, and would the other one work with the quad just as well?
I'm using the version 1, but I think the version 2 would also work fine.
Allow me to be the first to congratulate you on the grand prize win! Well deserved!
Thank you! I'm glad people like it and I hope there will be swarms of PCB quadrotors in the near future.
guys i have an idea...see i wanted to build this but it is too expensive i mean like 300$? ya like ma parents are gonna give me that so i wanted to make the worlds most cheapest quadrocopter!!! and i really mean it ..in this one he used an xbee which is really expensive plus he didnt add the cost to make the transmitter so add another 50 to 100 bucks so total about less than 500$? <br />so i had abt module laying around so i thought hey why cant we make a bt quadrocopter instead of an r/c?(cheaper u can get two modules for like 15 $ at ebay one for transmitter and another for reciever <br /> <br />most probably ill make this one and maybe make an instructable for u guys <br /> <br />by the way awesome instructable(this) well explained well done!!!
The total cost for everything including the ground station transmitter hardware (XBee, XBee Explorer, Game Controller) is about $320. Without the transmitter hardware it's $240. It's definitely not the cheapest project, mostly because I built everything from scratch. <br /> <br />Bluetooth would be cool, but the range isn't as good as the XBee Pro. It would be perfect for indoor use though, and then you don't need an adapter for your computer if it already supports Bluetooth. Or maybe a smartphone-based controller. That would certainly bring the cost down.
VERY NICE INSTRUCTABLE!! <br> <br>You can try KiCad Open Source solution instead of Eagle. <br> <br>Best regards from Uruguay! <br>Tabar&Atilde;&copy;
When two worlds collide, I read your excellent instructable then came across this <a href="http://www.dailymail.co.uk/news/article-2154283/Cats-away-Artist-turns-dead-pet-flying-helicopter-killed-car.html?ITO=1490" rel="nofollow">artist who turned his dead pet cat into a helicopter</a> (yes, you read right!). Probably the funniest and most morbid thing I read in a while. So if you want to expand your quadrotor in a new direction.....
Really, there should be a category for Super-Awesome-Advanced-Level-Instructables. Also, you could have taken it to an even higher level by including the ATmega328 from the pro mini on the PCB itself and maybe the inertial measurement unit too. <br>Extremely detailed Instructable +10
Thanks! Putting the ATmega328 on-board is definitely something I want to do in a future revision. Or maybe somebody here will do it first. ;) <br> <br>I'm not sure about putting the accelerometer and gyro on-board, though, because they wouldn't be isolated from mechanical vibrations.
Awesome instructable. <br>Have you tried using any Kalman filtering?
Thanks! No, I haven't tried any Kalman filtering. The complementary filter handles gyro/accelerometer merging very nicely in this application, and with very few lines of code. <br> <br>If I wanted to merge in more data, such as the magnetometer, or GPS, I might consider using a Kalman filter.
Really cool! I was watching the first video and I went, &quot;hey, that's Building 13!&quot;
unbeleivable great work <br>
&iexcl;Aye dios m&iacute;o!<br> <br> This is more like a Masters Thesis than an Instructable. Need a new website for Incredible Instructibles. I don't think I've ever given 5 stars before.&nbsp;
Hi <br>This is awesome work, well done! <br>But when u say it doesn't fly itself, what do you mean? It cant be as bad as trying to fly a traditional helicopter can it? Does it at least self stabilise? Keeping itself in the air, but just wander in all directions? <br>Im also curious about control differences between the early days and now after refinement? When you started off, could it be held in the air by someone with great flying experience, or was it simply uncontrollable by anyone? I would suspect it was unflyable, so how long was it before it was flyable by anyone? <br>I think these factors are important for anybody making these, like me at some point, to know what piloting skills and technical tweaking, trimming was required, etc. as I am no engineer like you clearly are. <br>thanks!

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