This is a remote-controlled aircraft project based on Arduino and XBee modules. The aircraft’s movement is controlled through a brushless DC motor and three servo motors. It has an XBee-based remote control at the transmitter end and an Arduino-based aircraft at the receiver end. The aim of this project is to develop a 4-channel wireless remote control (RC) system with one XBee each in transmitter and receiver.
Circuit and working
Fig. 1 shows the circuit of XBee-controlled aircraft transmitter section and Fig. 2 shows its receiver section. The circuits are built around Arduino UNO (board1), a pair of XBee module (XB1 and XB2), electronic speed controller (ESC) module, three servo motors (M1-M3) and a BLDC motor (M4).
Transmitter section is driven by a 3.7V battery and receiver section by an 11.1V LiPo battery. 11.1V is used to power the brushless DC motor (or BLDC motor) through ESC module. The Arduino board1 receives power supply from 11.1V battery at its Vin input pin.
The four potentiometers in transmitter section are used for sending different control signals to the receiver section through RF modules. Control signals received in the receiver are processed by microcontroller in the Arduino, which in turn controls a BLDC motor and the servo motors for rudder, aileron and elevator of the aircraft.
Arduino Uno board. Arduino is an open source electronics prototyping platform based on flexible, easy-to-use hardware and software. It is intended for artists, designers, hobbyists and anyone interested in creating interactive objects or environments.
Arduino Uno is a board based on ATmega328 microcontroller. It consists of 14 digital input/output pins, six analogue inputs, a USB connection for programming the on-board microcontroller, power jack, an ICSP header and a reset button. It is operated with a 16MHz crystal oscillator and contains everything needed to support the microcontroller. It is very easy to use as the user simply needs to connect it to a computer with a USB cable or power it with an AC-to-DC adaptor or battery to get started. The microcontroller on the board is programmed using Arduino programming language and Arduino development environment.
XBee module. XBee is a small 2.4GHz transceiver with a small microcontroller on board. It is a communication protocol which is used in many other instruments too.
There are two types of XBee radio transceivers: series 1 and series 2. Each series has two varieties: normal and pro. While the normal has a range of 30 to 40 metres in indoor or urban situations, along the line of sight it works up to 100 or even 125 metres. The pro is effective up to 1.6km on line of sight. However, with a Yagi directional antenna, XBee pro can reach as long as 20km on line of sight.
While series 1 has eight digital I/O pins, series 2 has 11 pins. Series 2 is more advanced and can be made into mesh networks whose range can be extended to any length by putting router XBees in between.
Analogue input and XBee
XBee analogue input pins read 0V to 1.2V maximum. Any voltage above 1.2V is treated as maximum or 1. Since most XBees operate at 3.3V, we reduce this voltage to 1.2V by adding a suitable resistor along the input device.
Suppose the analogue sensor is an LDR whose impedance varies from 0 to 10k, to drop 3.3V to 1.2V across the LDR we put a 20k resistor in series with the LDR, so that two-third voltage (of 3.3V) is dropped before reaching the LDR.
Transmitter side. Pins 20 through 17 of XB1 are connected to four 10k presets (VR1 through VR4), which are used to control BLDC motor (refer Fig. 4), rudder, aileron and elevator, respectively.
Receiver side. Pins 0 and 1 of board1 are connected to pin 2 and 3 of XB2. Pins 9, 11, 10 and 12 of the board are connected to signal pins of M1 (elevator), M2 (rudder), M3 (aileron) servo motors and ESC module (refer Fig. 5), respectively. Main body parts of a typical RC aircraft are shown in Fig. 6.
BLDC motor is used for propeller of the aircraft. The propeller, or airscrew, converts rotary motion from motor to provide propulsive force. It is the most important part of the aircraft. The propeller is mounted on the front side of the aircraft and is generally made of two or more blades.