Step 3: Circuit Design

The software I used is CadSoft EAGLE 5.11.0 which is a schematic and PCB editor, EAGLE provides a free version for download so anybody can use it. Right now they are actually distributing version 6 but my files are for 5.11, just so you are aware. A lot of custom components had to be created within EAGLE, and if you need them for other projects, EAGLE should have a script called "export library", so use that to extract my custom components if you ever need to. 

The quadcopter needs to be light so we can only use a small battery. The battery must be rechargable and can provide enough current for the four motors. So a Li-poly cell is selected. Knowing the rough size I'm aiming for already, I went to Hobby King and picked out a small cell that is rated 350mAH and 20C.

Now I know I'm working with 3.7 volts. The ATmega128RFA1 is designed to be battery powered directly, but my sensors are not. I need 3.3 volts, so I need a 3.3V voltage regulator. Since the input voltage will be 3.7 volts, this regulator needs to be a low-dropout regulator.

A really basic power supply circuit is designed, inspired by example schematics from various datasheets. Higher voltage goes in, regulated voltage comes out...

Lithium batteries should not be over-discharged so battery monitoring is required. The ATmega128RFA1 has a battery monitor feature so that's taken care of already, no extra components required for battery monitoring.

I keep a bunch of MCP73831T lithium battery charging ICs around for any quick designs that require a lithium battery. They are tiny and easy to use. The battery charging circuit is designed using the examples provided in the datasheet of the MCP73831T.

The motor control circuitry is simple. The N-channel MOSFET acts as a switch (low side, which is friendlier for microcontroller controls). There are pull down resistors on the gate to prevent accidental activation, and series resistors to prevent the gate capacitance to draw too much current from the microcontroller during switching. There is a "flywheel" diode for each motor since they are inductive loads, so the diode is a fast switching Schottky diode that dissipates any stored reverse voltage during switching. The MOSFET itself has to be able to handle the amount of current required but also needs to be small, I chose one that can handle 1.15A and in SOT23 packaging.

The brains of the circuit are the two ATmega128RFA1 microcontrollers. They need a 16 MHz clock source for two main reasons: the radio transceiver requires it, MultiWii and AeroQuad code are designed for it. So there's a 16 MHz crystal for each microcontroller, and load capacitors for the crystals. I also know I need at least MOSI, MISO, SCK, and RESET signals to be connected to an AVR programmer later so I can program the microcontroller. The serial port signals are also connected so I can debug and use the computer's graphical configuration and monitoring utilities. The power pins are properly decoupled with capacitors. The radio circuitry consists of a BALUN to match the 100 ohm balanced output of the microcontroller to a unbalanced 50 ohm impedance antenna. The circuit is mainly derived from the datasheet's example circuit, and Zigduino's schematic.

The PWM pins are connected to the motor control circuits so the microcontroller can control the speed of the motors. I added some LEDs. The sensors and Wii Classic Controller all connect to an I2C bus. (in "version 1", I omitted pull-up resistors on the I2C bus, apparently the ATmega128RFA1's internal pull-up resistors didn't work, so "version 2" has these resistors added).

The sensor circuitry is also derived from their perspective datasheets, and looking at SparkFun's breakout board designs (because AeroQuad uses those breakout boards).

In "version 2", I improved the transmitter design by adding a FT232R chip, this added a USB virtual serial port, which works with the MultiWii and AeroQuad graphical utilities.
Hi, great project! What kind of modificativos would I have to do on aeroquad motor library to Adjust PWM for brushed motors with MOSFET instead of ESC?
<p>I'm new to the site so I don't quite get it, only premium accounts have access to the pdf file? My cousin would love this, though</p>
<p>only if i had money and acsses to those parts... !</p><p>Awesome project :D</p>
<p>I don't understand how you made the circuit board and receiver.. You just took a PCB you had laying around, took all the componets off of it, and BOOM! quadcopter! Can you explain this to me?</p>
<p>They were custom designed and ordered from on online PCB manufacturer. BatchPCB is a popular one. He then soldered all the necessary components on.</p>
<p>I ordered the PCB's and built this. This is an advanced user project. The chip packages are QFN and a challenge to solder. Total cost was approx $200. I could not get parts of the TX code to compile, and had to modify. The author considers this a &quot;old&quot; project and does/will not support or help.</p>
<p>Hey there, your <strong>Picopter </strong>got me inspired and all and made we want to build a copter on my own for like $40. I will have some access to a <strong>3D printer</strong> so that will add another $5-10 to the cost. Here is the plan and I need suggestions and comments.</p><p>First of all, I'm not going to print a pcb but I will be using a 3D printed plastic frame and the same motors I think you did.</p><p>- <a href="http://www.ebay.com/itm/221541787818?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT" rel="nofollow">DC 3.7V 48000RPM Coreless Motor Propeller</a></p><p>That leaves me to a question if the copter will even lift itself if I use the following electronics which add on some more weight.</p><p>- <a href="http://www.ebay.com/itm/251383404458?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT" rel="nofollow">3.7V 200 mAh Li-polymer Rechargeable Battery Li-Po</a></p><p>- <a href="http://www.ebay.com/itm/321361180496?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT" rel="nofollow">NRF24L01+ 2.4GHz Antenna Wireless Transceiver</a></p><p>- <a href="http://www.ebay.com/itm/131231041891?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT" rel="nofollow">MPU-6050 3 Axis Gyroscope and Accelerometer Sensor Module for Arduino</a></p><p>- <a href="http://www.ebay.com/itm/400362466832?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT" rel="nofollow">HMC5883L Triple Axis Compass Magnetometer Sensor</a></p><p>- <a href="https://www.sparkfun.com/products/retired/11780" rel="nofollow">Tennsy 3.0 32 bit ARM Cortex-M4 48 MHz CPU, 128K Flash Memory, 16K RAM</a> (about the same weight as the Arduino Pro Mini)</p><p>You didn't specify the weight of your copter but I bet you give me a suggestion.</p><p>Thanks OP!</p>
<p>how to make pre account.... i want this download</p>
<p>Brilliant you made one! I bought one of the Hubsan branded ones which is fantastic, far easier but far smaller than the massive 5 foot bladed gas powered 60 size XCEL I had in my youth - that things was lethal!</p><p>Nifty way to charge it and avoiding RF interference. I am impressed, did you get three or one gyros in there?</p><p>Call it 'Quaddy' or 'Quadtastic!&quot; or &quot;4play&quot; </p>
<p>i wanna this pdf and iam not haver premium account</p><p>plz can any one send to me <br>on teet_totti@yahoo.com</p><p>pleas</p>
<p>Awesome!</p><p>Will you sell this project as a kit?</p><p>How much you will charge for one?</p><p>I want one for me.</p><p>Congratulations.</p>
<p>first time to know about ATMega128rfa1..<br>and i wanna get one.</p>
<p>Very nice man. Less of a project than I would have imagined it to be actually.</p>
<p>I dont have the wii remote controllers can I use any thing else? How to use it? </p>
want :0 how much? :3
<p>Hit us with that price :3</p>
i want one too :D
how much would it cost to buy one from you?
<p>does it fly???</p>
1) can you add a wireless camera on the picopter 2) can you add a gps module on the picopter 3) can you controll th picopter from anything other than the wii classic remote
Hi, <br>I have viewed this project you have built, and was quite interested in making one my self, would you be able to help me out with getting the PCB's and programing it?
you did a great job with this <a href="http://www.intorobotics.com/5-best-examples-of-how-to-build-a-diy-quadcopter/" rel="nofollow">powerful DIY quadcopter</a>
sir,i'm getting more confusion at the time of programming.can u show me how to install every code into picopter.from so many days,i'm working on it.i'm completed the hardware stuff fully,but totally failing in programming.please give me a installation video or step by step installation.kindly thanking you
can you give step by step instructions, its for my son's school project and i want to thelp him but unfortunately i only to operate a computer
sir , <br>from where to get those 2 green plates 1 for quadracopter and 1 for transmitter and what is there plate number .plz tell fast i wanted to make and sir as i wanted to order somethings at digikey.com there are comming 3 options all are same but there is comming tape and reel,cut tape and digi reel. which one i should select...... plz tell fast sir plzzzzzzzzzz
sir plz tell me name of all parts and their types used in making picopter.plz mail me the list at ckhurana79@yahoo.com . plz tell me fast. i love makin this type of things
How much did this project cost?? My friend got one of those really cool Parrot AR Drones and i want to build something similiar so we can do cool stuff with them. Maybe even launch this thing off of the botton of the big one. Where did you order the custom PCBs?? would love to build this!
Just fyi: <br>I ordered all parts at Digikey, Sparkfun &amp; ebay and ended up paying 190 euro incl. shipping to EU and printing 3 qc/tx pcbs. I was expecting something among 100 euro but I didn't want to go back after ordering the first parts :) <br>Batch ordered, a kit might cost something around 150 euros I'd guess. <br> <br>It's amazingly easy to find everything you've listed here; no exotic parts or anything, in fact, hardest part is finding a cheap li-po. <br> <br>Do you have any idea how much payload this thing can carry? Or what flight time you achieve with whatever battery you're using? <br> <br>Impatiently waiting for my orders... 8)
Any chance you have the parts list still? I seem to be overlooking it or just don't know where to look. Thanks.
would you consider makeing this as simple kit that can be bought. You would make some serious cash.Also is there a way that bluetooth can be implumented into the circuit somehow.
great little device, like to see it flying <br> <br>Maybe i got an idea for you to use different propellers. <br>The problem with these propellers is that people put their fingers to near to it, or they get damaged when you hit something during flight, Maybe you remember thse kid toys : <br>http://www.papstar-products.com/papstar_pe/prodpic/4-Toys-Flying-propeller-18909_b_0.JPG <br> <br>i think if you raise the outer circle a bit (strip of thin hard sheet) it would improve the blade too (better earodynamics for end of proppellor.)
Very neat. <br> <br>Instead of using jumper blocks, have you considered these plunger switches? <br> <br>http://www.goldmine-elec-products.com/prodinfo.asp?number=G15214 <br> <br>They're less of a hassle and they'll fit the same footprint assuming you're using 2 * thru hole .1 inch headers. If you're using SMT headers for the jumpers, still doable but will require bending the switch pins and perhaps a dab of hot glue.
hi,sir i need quadcopter's blank circut's print can iget it sir <br>
please sir please sir help me
sir can you write the list of parts used in the circut board <br>
if you can't find this stuff on here, what makes you think you can build this thing?
sir can you write the list of parts used in the circut board <br>
A complete product and a true feat of engineering. This is excellent!
hai frank you make all this by your self .... wow it's cool i want the make this where i can get the component???
You can get the components by searching DigiKey for the part numbers I provided, they have almost everything. Some of the stuff you can't find, you'll need to visit SeeedStudio, SparkFun, and Google.
For the mainboard ?? Were I get that?
You have to send the design to a PCB manufacture to have it made for you
you make this circuit board all By yourself?you are amazing,my dream is make a flying tiny robot but too bad i not pro in electrical : (
Are you planning on producing these boards to sell? If so, I will gladly buy one!
I would like to try, maybe attempt a &quot;Kickstarter project&quot; or something.
Kickstarter could be a great way to do this. You'll need a solid business plan and some flashy videos of your prototype flying well, but I think you'd get a lot of interest now that quadcopters are all the rage.
I agree, this could really take off on a service like kickstarter. it's small, open source, uses standard inputs from the wiimote, well designed, and developed privately to be a legitimate tool/aircraft. The geek media is clamoring for stuff like this, especially since the release of the <a href="http://youtu.be/_sUeGC-8dyk" rel="nofollow">quad copter videos at Upenn</a>.<br> <br> -yes there is a pun

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Bio: I am an electrical engineer. I graduated from U of Waterloo. I used to work for Adafruit Industries as an EE. Now I work for ... More »
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