PCB Quadrotor (Brushless)

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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.
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calmlunch2 days ago


clickyummy1 month ago

found this blogspot by shane: 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.

bearblue1 month ago


patriots213 months ago

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.

cgrrty4 months ago
mark !very cool
Combatraffi6 months ago
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?
scolton (author)  Combatraffi6 months ago
It is a little unclear in the datasheet. Right above the High Pass settings, starting on p.29 of, there is a setting for "DR and BW" (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.
bgumelar11 months ago
how long this quadrotor can fly??
scolton (author)  bgumelar6 months ago
Flight time is about 8 minutes, depending on the size of the battery.
susan1119 months ago
Hi, i think u did a great job. at least, i think it's a tall order for me. though i love href="">rc helicopters, i still knew
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!
susan1119 months ago
Hi, i think u did a great job. at least, i think it's a tall order for me. though i love href="">rc helicopters, i still knew
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!
patriots2110 months ago
found this blogspot by shane: 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.
patriots2111 months ago
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.
hdman12031 year ago
excellent project and videos. i saw a TED video of this a while back really wanted to do this.

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!!
scolton (author)  hdman12031 year ago
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 "return to horizontal" 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.
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?
scolton (author)  danblakemore1 year ago
The weighted IMU sat on top of the foam loop.

I also have a Talon'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.
zaphv1 year ago
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 ?
scolton (author)  zaphv1 year ago
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.
Alastor1361 year ago
I was about to ask if you were affiliated with MIT, then I noticed you were testing it in Building 7!
Bill WW1 year ago
Congrats on the win!
You provide excellent specs on components.

TechNotes1 year ago
How did you choose your motors?
scolton (author)  TechNotes1 year ago
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.

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?
scolton (author)  TechNotes1 year ago
Yes, that's the exact one I used.
TechNotes1 year ago
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?
scolton (author)  TechNotes1 year ago
I'm using the version 1, but I think the version 2 would also work fine.
WYE_Lance1 year ago
Allow me to be the first to congratulate you on the grand prize win! Well deserved!
scolton (author)  WYE_Lance1 year ago
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$? ya like ma parents are gonna give me that so i wanted to make the worlds most cheapest quadrocopter!!! and i really mean it this one he used an xbee which is really expensive plus he didnt add the cost to make the transmitter so add another 50 to 100 bucks so total about less than 500$?
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

most probably ill make this one and maybe make an instructable for u guys

by the way awesome instructable(this) well explained well done!!!
scolton (author)  francisroan1 year ago
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.

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.

You can try KiCad Open Source solution instead of Eagle.

Best regards from Uruguay!
blanchae1 year ago
When two worlds collide, I read your excellent instructable then came across this artist who turned his dead pet cat into a helicopter (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.
Extremely detailed Instructable +10
scolton (author)  udawatabhimanyu41 year ago
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. ;)

I'm not sure about putting the accelerometer and gyro on-board, though, because they wouldn't be isolated from mechanical vibrations.
Geraldes1 year ago
Awesome instructable.
Have you tried using any Kalman filtering?
scolton (author)  Geraldes1 year ago
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.

If I wanted to merge in more data, such as the magnetometer, or GPS, I might consider using a Kalman filter.
Trebawa1 year ago
Really cool! I was watching the first video and I went, "hey, that's Building 13!"
unbeleivable great work
dchall81 year ago
¡Aye dios mío!

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. 

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