Introduction: All About Radio Control Aviation Hobby and a DiY Radio Transmitter for Electric Airplanes
Wikipedia defines RC-vehicle as
A remote control vehicle is any vehicle that is remotely controlled by a means that does not restrict its motion with an origin external to the device. This is often a radio control device, cable between control and vehicle, or an infrared controller. A remote control vehicle or RCV differs from a robot in that the RCV is always controlled by a human and takes no positive action autonomously.
This definition is partially correct thanks to controller boards with gps like APM 2.5 you can make your vehicle autonomous giving it gps missions or let it follow wherever you go.
AIRPLANES:
Wright brothers do invented airplanes as a means of transportation but you can definitely have fun out of it by doing aerobatics and for aerial videgraphy. I personally like rc airplanes the most as they are fun to fly and you can do tons of things with them like aerial videography, sporty aerobatics, throwing bombs or paraschutes , FPV(discuss later) etc.
There are variety of different airplanes classified under rc hobby. You may wish to skip this but I have added a link below if you wish to know more about them.
http://www.rc-airplane-world.com/rc-aircraft-types.html
Step 1:
Step 2: Understanding Terms Used in Rc Airplanes
By now you must be eager to make your very own airplane so lets
get familiar with some terms which you should know well before any scratchbuild
1 POWER SYSTEM:
In rc hobby you can power you planes either on gas(NITRO) or electric. This tutorial will be focused on electric power plane as gas engines are difficult to handle and aren't cheaply available.
BATTERY:
In rc hobby we generally use Lithium Polymer (Li-Po) batteries as they are small, cheap and have high discharge rates. These batteries are available in different capacities.
While choosing a LiPo battery you must consider the following aspects
1) The S-rating
1s,2s,3s or 4s are just the cells your battery contains. So 1s means one cell and 3s means 3 cell and so on. 3s is most common for begineers. Each cell in lipo can supply 4.2 volts at full charge so a 3s battery can supply 12.5(approx.) voltage. So for now consider a 3s battery as ideal for your use.
2) Battery capacity:
Commonly known as mAh rating tells how much is your battery capacity.
For eg a 2200mah battery has more capacity than 500mah battery hence it will last longer and gives more flight time. It is to be noted that a more capacity battery do gives you more flying time but it also adds up weight to your plane. So its not always true that more mAh means better battery. :p
3) The c-rating: The c-rating tells about maximum current discharge capacity that your battery can supply. Consider following formula:
Ah X ‘C’ rating=max amps draw
For eg a 1000mAh 20c battery can supply
1AhX20C=20 amps continuously.
So when buying a battery it is supposed to be as follows:
2200mAh 3s, 20C LiPo.
1300mAh 2s, 30C LiPo. Etc
Battery Charger:
So definitely you are going to need battery charger to put back the capacity you drqained out of it. A battery charger needs to be good enough which can supply continuously current to all the cells simultaneously. There are tons of different battery charger available in the market.
NOTE: when dealing with LiPo it is to be consider that draining the battery and exploiting it can cause permanent damage to battery and it may not charge later. Also these batteries can catch fire easily if more amps are drawn out of them than C rating or it is overcharged so always use a fire safe bag while charging them. Also never drain them beyond certain limit for eg a Lipo 3s should never be drained below 9.2volts and so. To check use battery monitor or battery low Indicator. Also use balance plug while charging, this ensures that all the cells are charging at same rate simultaneously,
· The motor:
As I have already told you that we’ll be using electric powered planes we will use motor that runs on battery power. A motor that is powerful enough to lift your plane model up in the air. Hence we will be using brushless motor for airplanes.
Unlike brushed motor they don’t have any contact brushes which reduces overall friction and increase its efficiency.
While buying brushless motor consider following things:
x-y A where
x: diameter of the motor in inches
y: Length of motor in inches
A: KV rating of motor.
KV explained: kv means RPM/volt (not kiloVolts) it shows how many revolutions your motor will spin in a minute at one volt.
For eg 22-08 1000kv motor says its diameter is 22 inches, length of 8 inches and spins 1000rpm at one volt.
Say u are using a 12 volt battery than it will spin 1000X12= 12000 rpm ideally.
Great to lift your plane hah? Some motor also has a power rating and a propeller chrt(discussed later).
Also there are two types of BLDC( short for brushless motor):
1) Inrunner
2) Outrunner
Generally outrunners are used.
· ELECTRONIC SPEED CONTROLLER:
As I have told you BLDC have no brushes it rely on rotating magnetic field to spin, which comes from 3 phase Alternating current (AC). So to convert battery dc power to 3 phase AC an ESC is used.
ESC has following arrangement:
3 wires at one side, two wires on one side and a servo 3-wire connector.
3 wires goes with 3 wires of motor.
2 power wires are connected to Li-Po battery
Servo connector does two things
1) It supplies 5v to receiver to power it, this is generally called battery eliminator circuit or BEC. Generally all the ESCs today comes with BEC.
2) It takes PWM input from the transmitter and rotates motor with desired user speed.
· The propeller:
Propeller is the most important and most cheap part of your power system. It goes with the motor to give appropriate lift to your plane.
While buying a propeller consider following details:
· ‘A’x’B’ where:
o A is the diameter of the prop in inches
o B is the pitch of the prop in inches.
Diameter is nothing but the length of the propeller say 4 inches.
Pitch tells how much your plane will move forward when your prop completes one full revolution say 2 inches. So it makes a 4X2 propeller.
· Propeller Material: Props are generally made of wood, carbon fiber and plastics. Wood used for gas powered planes and we generally use plastic for our bldc planes.
It is to be noted that generally a small diameter and large pitch prop goes with larger kv motor and a large diameter shallow pitch prop goes with less kv motor.
For eg my 2200kv motor uses 6X4’’ prop and my 1000kv motor uses 10x6’’ prop.
Thrust: Motor with propeller gives thrust to lift the plane. The latter arrangement gave me thrust of 1100 grams.
PUSHER VS PULLER PROPs:
When you research more in this hobby you will find that there are two types of planes categorized as pusher or puller. As the name suggests puller has motor and prop at the front and it pulls the plane forward while in pusher this arrangement is at the back and it pushes the plane forward. So the prop cutting are different for different applications but it is easy to use one prop for both. It is as easy to reverse prop direction by just interchanging any two wire between esc and motor which will make motor spins opposite direction and behave as pusher.
Step 3: Lets Build an Airplane
So by now you know enough of the power system so lets get
started with our scratch build:
For your first build I would suggest you to go with the design already build and tested by thousands of people. I’ll not cover how to make plane here but I’ll suggest you tutorials which will help you build you plane in just matter of a day.
Material used for building planes:
· Depron: most common material for building planes. Falls in category of foam which is Very light, comes with paper lamination on both or either side. In USA adam reddy’s board are used for making planes.
· Corrogated EPP foam: similar to depron in lightness but has slightly different properties.
I would suggest to use 6mm depron for your first build. Links to which are attached below
Step 4: Steps in Building Your First Plane
I suggest you to build
a plane called FT-Bloody Wonder by FliteTest as your first plane as it is great for beginners and can take vertical takeoff from ground. So order following parts :
Foam Board [http://www.goadams.com/]
Motor[http://www.hobbyking.com/hobbyking/store/uh_viewit...]
ESC[http://www.hobbyking.com/hobbyking/store/uh_viewit...]
Batteryhttp://www.hobbyking.com/hobbyking/store/uh_viewit...[]
Servos[http://www.hobbyking.com/hobbyking/store/uh_viewit...
You can cut plans from their website
[http://assets.flitetest.com/article_files/FT-Blood...]
[http://assets.flitetest.com/article_files/FT-Blood...
To make any plane in general all you need to do is :
· Print out plans which some good people and communities have posted free online like flitetest.com. These plans are in A4 sizes.
· Align the plans correctly number wise to make a large full plan.
· Tape this plan on you foam board.
· Cut out the outlines, score or crease the areas as suggested by the plan designer. Have a look on the following scratch build video.
· After you cut out plane parts you will have following:
o Fuselage or main body part where your battery will reside.
o Wings(With Ailerons)
o Horizontal stabilizer with Elevator(used to lift plane up n down).
o Vertical stabilizer with rudder(used to align plane left and right in air or grownd)
The Elevator, Rudder and Ailerons makes up the control surfaces of your planes.
Elevator is used to lift plane up and down in air.
Ailerons are used to align plane left and right in air.
Rudder gives extra level of control and similar to ailerons but gives better control on ground if you plane has landing gears and you want to launch it from ground rather than hand launch.
These control surfaces are controlled using servo motors, generally 9g analog servos which are cheaply available.
Control Surfaces with Throttle(BLDC) makes channels of your plane.
So a 3 channel plane generally have Elevator, Rudder and Throttle.
4 channel plane have Throttle, elevator, rudder and ailerons.
5 channel may have additional bomb dropper.
· So you cut out plane out of your foam board, next is to glue all the parts together to give it a shape. Use a high power flue gun and glue sticks. The complete scratch build video for bloody wonder by FliteTest is at :
[
. I've posted few pics of my latest build.
Step 5: THE TRANSMITTER
You build you plane successfully now what? Yeah i know you want to fly it but wait you don't have a remote. If you have budget definitely go and buy one for you it will give you lot of utilities. Transmitter in rc are generally works on 2.4Ghz frequency. Consider Flysky FS-T6 which is best budget transmitter for begginers. You can buy it from
http://www.amazon.com/Digital-Proportional-Channel...
it is a 6-channel transmitter which means you can use 6 different control surfaces and it comes with a reciever which you can hook to your plane. It gives you around 600 metres of range.
It has an LCD which will help you program it for your plane: it will give you features like:
Channel reversing
DualRates and Expos
V-tail mixing
Channel mixing
Auxillary channel configuration
etc
. The transmitter comes with reciever, check for how much channel reciever supports. You can also buy seperate recievers compatible with your radio system.
Step 6: DIY Transmitter
Buying a transmitter gives you variety of features and flexibility but I know its expensive. Don't worry you can make your own , very own transmitter with Arduinos lying in your cupboard /m\.
When I build my first plane i ran out of budget and have no money left for transmitter so I decided to build onw with arduinos lying around. So if you too wants to build one go and order following:
I ordered my NRFs and joystick from China which took 20 days to deliver and they are cheap enough and works great.
2-Arduino UNO or clone from local Radioshack
2-NRF24L01 PA+LNA
[http://www.aliexpress.com/item/2pcs-lot-Special-promotions-1100-meter-long-distance-NRF24L01-PA-LNA-wireless-modules-with-antenna/969949629.html]
2 Joystick modules
[http://www.aliexpress.com/item/Free-Shipping-New-f...]
Male to Female wires, from ebay
Lets get Started.
The transmitter or remote is made up of arduino uno, one nrf24l01pa+lna, 2 joystick modules and a battery source.
The joysticks are nothing but two axis potentiometer with dommon ground and a switch which activates low when joystick is pressed. So joystick modules have 5 pins in total
Vcc---> 5v on arduino
Gnd---> gnd of arduino
X-------> A0 of arduino
Y--------> A1 of arduino
Sw------->D of arduino (D= Any free digital pin of Arduino Board, change the pin number in sketch accordingly).
Similarly second joystick pins goes to
A2,A3 amd switch pin to D respectively
Nrf module on transmitter side goes to SPI bus of arduino with pins described as follows:
CE--> D9 of arduino
CSN--> D10
MOSI-->D11
MISO-->D12
SCK--> D13
VCC---> 3.3v, donot supply 5v else you will fry it.
GND---> gnd pin of arduino
IRQ--> Not connected
To interface NRFs with arduino you will need NRF24 library of arduino by Maniacbug:
Download it from the link below:
https://github.com/maniacbug/RF24
Also dont forget to import SPI.h library
The transmitter generally have a free joystick springless which donot returns back to centre when you leave it , but unfortunately the joysticks which we're using returns back to centre when you leave it leaving you to half throttle. I removed the spring by desoldering it to pcb and than resoldering, Tinker your joystick modules and lets see if you can.
Also the tx is in beta am working further to add a graphical LCD with Atmega2560 but for now no LCD.
Since I dont have a 3D printer or laser cutter I house the whole transmitter circuit inside an old mobile phone box and painted it. I've attached pics for you. If you have a 3D printer definately use it for casing.
Step 7: Receiver Circuit
So now its time to build reciever circuit, which is excately same as transmitter with a difference that in place of your jousticks you are going to put your bldc and servos on rx side.
NRF TO ARDUINO
Same pins as that of tx
MOTORS:
BLDC:
Red/Orange---> vin pin of arduino
Black/Brown---> gnd pin of arduino
Yeah you can power your arduino with esc servo connector so no need of extra battery on rx side ;)
White/signal wire to D pin of arduino.
Reciever in full arduino uno form adds weight when put inside the plane fuselage so you can make a custom pcb and mount only atmega chip and nrf to plane without full uno. Check arduino on breadboard on arduino.cc for more detials. PCB designing is out of the scope for this tutorial so DIY,
So you are ready with rx and tx circuit now lets flash the code.
Download the code from my github repo. The code is well commented and self explainatory however I've tried to explain what is happening at arduino side in later steps.
https://github.com/iayanpahwa/DIY_RC_TRACNSMIITER_2.4GHz
Step 8: Code Transmitter Side
The transmitter code is very simple
Firstly it initializes the spi bus, makes a radio for connection
Secondly it takes input from the joysticks and maps it to the value suitbale for your motors.
Finally it sends the values to receiver.
Step 9: Code Receiver Side
Receiver saves the code in array and passes it to motor.
We have used servo.writeMicsoseconds for BLDC and simply servo.write for servos.
You can trim your control or reverse servos in the code by changing suitable values.
It is to be noted that since we dont have extra channel for ailerons we will control ailerons using buttons which activates low when joystick is pressed on receiver side.
So when you press left joystick left ailerons are activated and similarly for right aileron.
The best way to tinker it is to use an accelerometer for controlling plane with gesture ;)
Step 10: Good Habits in Rc
The designer have marked CG points on plane. Put your fingers at that point and check for proper balance and adjust battery forward and backward to get proper CG.
NEVER FLY LET YOUR FLIGHT DEGRADES YOUR BATTER BEYOND A CERTAIN LIMIT. FOR A 3S battery never let it drops below 9.4volts.
Keep text of your propeller face outwards.
To reverse direction of BLDC JUST SWAP ANY TWO WIRES FROM ESC TO BLDC.
Always try to launch plane in the direction of wind.
Fly in big open grounds, avoid obstacles.
Step 11: Where to Go From Here?
Whats next:
I have linked up few sites and tutorials to help you know better and better of rc hobby. Also if you wish to make more such planes you can download free plans from sites below.
FPV: stands for first person view is technology where you can view exact scene which your plane is seeing from air in real time using ground telemetry technologies. More on FPV? Check link below
Multicopters: multicopters are next step to rc before making a multicopter just have a look on few tutorials as these are different from planes in a way that they need extra control and requires sensors to stabilize in air with complex logics like PID. Hence we use controller boards for multicopters.
Good luck, and welcome to rc world.
If you like my tutorial please do give me a thumbs up and vote so that I could win the competion.
Thank you
More to come in near future.
Comments are welcomed,
www.flitetest.com
Maker Hangar 1 and Maker hangar 2 on youtube
Free plans:
http://www.parkjets.com/free-plans
Introduction photo courtsey. (FliteTest fb page).
We love FliteTest.com :)