24-08-2012, 02:32 PM
RC Car Controlled by WiFi with an Android
carcontroller.pdf (Size: 782.46 KB / Downloads: 353)
Objective
The goal of the project is to pilot a RC model via an Android smartphone.
This document is an abstract of the one I wrote for a project for my last
year at the Polytech'Tours engineering school in France.
Presentation of the car
The car is a NE14 by NIKKO. The battery is 9,6V. With the original elec-
tronic board, it lasts 15 min. The board will be replaced by a prototype
board with the Flyport. To controll the car, you have 2 motors to deal with:
The rst motor is used to change the direction of the car. The servo-
motor I used is a HITEC HS-322HD which is a lot more easy to use
than the servo in the car (6 wires).
The second motor is used to change the speed of the car. It has to be
driven by a Hbridge to enable the car to move forward and backward.
This motor is powered directly by the car's battery.
Electronic
With the Flyport you will have to use 2 PWM, 2 digital output and the
WiFi communication (UDP connection).
To controll the car with the Flyport I had to develop the following parts:
voltage adaptation 9,6V to 5V
Hbridge circuit
The voltage adaptation is done with a LM7805 by Fairchild. The com-
mand of the propulsion motor is done with a SN754410NE by Texas Instru-
ment. You need 1 PWM and 2 digitals ouputs (out1 & out2) to controll the
motor. To determined the duty cycle of the PWM I used an Arduino board.
if out1=1 and out2=0, the motor goes clockwise at the speed set by
the PWM
if out1=0 and out2=1, the motor goes anti-clockwise at the speed set
by the PWM
The servo for the direction is controlled by a PWM. The duty cycle of the
PWM in function of the angle of the servo (0-180) has been determined with
an Arduino board.
The gure 3 represents the electronic schematic. The gure 4 repre-
sents the electronic test board which is embedded in the car. The gure 2
represents the duty cycle of the PWM in function of the angle of rotation.
Test
The Hbridge used is limited to 1A and the propulsion motor requires lot of
power to run at full speed. There is no problem when the tyres are in the air
but when the car is put on the
oor, the motor will drawn to much power
and will not move as fast as it should. A friend of mine advised me to use
a LMD18200T (Hbridge) but I didn't try it yet. With the original battery,
the car works for about 10min. It exists battery of the same size which can
last 40min.
Integration
The servo I choose perfectly ts in the frame of the car. I had to cut the
plastic to allow it to turn. The upper part of the frame has been removed
because it was dicult to receive the wi from the car. The gures 7 and 8
represent the integration of the board in the car.