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MOBILE CONTROL SMALL CAR

In this project we show that how we control the movement of any small robot with the help of mobile phone. By using this logic we not only control the movement of  vehicle but also switch on/off other accessories on robot.

 

          Our project is to be divided into few parts.

 

Vehicle control.

Supply circuit

GSM control.

 

 

CONCEPT:

In this project we use smart logic and control system of embedded system by using microcontroller. In this project we use ic 89c51 as a main processor.. microcontroller sense the signal and drive the motor of the robotic vehicle. .

 

Ist circuit is ic 8870.  IC   8870  is a bcd to dtmf decoder. So our first part of the circuit is our dtmf decoder. This part is very much necessary, without using this part is not possible to  interact with the  mobile phone or dtmf based any phone. Whenever we press any switch from the transmitter phone then transmitter transmit some signal as per the switch press. So on every press switch there is a different signal

 

Frequency

1209

1336

1477

1633

697

1

2

3

A

770

4

5

6

B

852

7

8

9

C

941

*

0

#

D

 

Output of the dtmf decoder is bcd.ur next circuit is how to convert bcd signal into decimal signal. In this project we use ic 74154 as a bcd to decimal decoder circuit. IC 74154 converts the bcd signal into decimal signal . Output of the 74154 is  active low.

Output of the  74154 is connected to the 89c2051 microcontroller. Ic 89c2051 microcontroller basically drive the motor for forward and reverse movement.

Output of the microcontroller is connected to the optocoupler circuit. Here in this project we use ic pc 817 as a  optocoupler to interface the  microcontroller to small slow speed dc gear motor. One gear motor drive the  vehicle and second gear motor change the front wheel of vehicle..

 

Power supply circuit.

In this project we use 9 volt battery to drive the vehicle. One 9 volt battery for the microcontroller circuit. Second 9 volt battery  drive  the motor driver circuit . Here in the project we one 5 volt regulator circuit. Output of the 9 volt dc is converted into 5 volt dc by using  7805 regulator circuit. Ic 7805 regulator converts the  9 volt dc into 5 volt dc with the help of the 5 volt regulator 7805.

 

 

 

 

 

 

VEHICLE CONTROL.

In this project we use two small gear dc motor for drive the  small robot. One motor for the back wheel and one motor for the front wheel. Back motor drive the both tyre at a time and front motor control the direction of the vehicle . Here we use powerful gear dc motor instead of stepper motor. Stepper is not suitable for the drive the vehicle. Stepper motor is suitable for  positioning sensor but gear motor is suitable for the  vehicle drive.

 

Motors

 

To make the robots mobile we need to have motors and the control circuitry that could control the motors. There are different kinds of motors available for different application.

 

1.     DC motor

2.     Stepper motor

3.     Servo motor

COMPOENTS USED IN THIS PROJECT:

IC 8870 . DTMF DECODER.  We use this ic in our project for mobile interface. By using this ic we decode the dtmf pulses from the mobile phone through hands free and  by using this ic we convert this pulses in to bcd signal.

 

IC 74154.  ic 74154 ic basically convert the bcd signal in decimal signal  for further use with the microcontroller. IC 74154 convert the 4 bit data in to 16 bit output. Here in this project there is no use of  16 output, so we use only 4 output.

89C2051 MICRCONTROLLER.

89C2051 MICROCONTROLLER. Is a 20 pin version of 51 family,. Program written for this controller is same for the 8051 controller. In this controller there is total 15 input and output pins. For controlling the process control.

 

OPTOCOUPLER ( PC 817) In this project we use optocoupler  to provide a electrical isolation between process control circuit and motor drive circuit. In this project we use separate supply for processor and control circuit. Pc 817 is 4 pin ic. In this coupler two pin is input and two pin is  output.

 

CRYSTAL.  In this project we use two crystal. One for the dtmf decoder and second with the microcontroller Main use of the crystal is to  provide a external frequency for the internal oscillator. With the  dtmf decoder we use crystal 3.58 Mhz and with the microcontroller we use 12 Mhz crystal.

 

DC MOTOR.  We use slow speed dc motor to drive the movement of vehicle. In this project we use two dc motor. One for the drive the vehicle and second motor to change the direction of the vehicle.

 

 

H BRIDGE LOGIC: H bridge logic is basically provide a  forward and reverse logic to the motor.

 

 

COMPONENTS USED:

IC 8870(1)

 

IC 74154 (1)

 

89C2051(1)

 

PC 817(4)

 

CRYSTAL ( 3.58 Mhz), (12 MhZ)

 

7805 REGULATOR.

 

NPN TRANSISTOR BC 548 (4)

 

PNP TRANSISTOR BC 558(4)

 

RESISTOR:

 

470 OHM(4)

 

4.7 K OHM (4)

 

1 K OHM (4)

 

22K OHM (2)

100 K (1)

10 K(4)

L.E.D(2)

CAPACITOR

1000mfd(1),

10 mfd(1), .

1mfd(104) (2),

22pf(2)

DC MOTOR ( GEAR MOTOR) 2 MOTORíS

 

DC motors

          These are the motors that are commonly found in the toys and the tape recorders. These motors change the direction of rotation by changing the polarity. Most chips can't pass enough current or voltage to spin a motor. Also, motors tend to be electrically noisy (spikes) and can slam power back into the control lines when the motor direction or speed is changed.

Specialized circuits (motor drivers) have been developed to supply motors with power and to isolate the other ICs from electrical problems. These circuits can be designed such that they can be completely separate boards, reusable from project to project.

A very popular circuit for driving DC motors (ordinary or gearhead) is called an H-bridge. It's called that because it looks like the capital letter 'H' on classic schematics. The great ability of an H-bridge circuit is that the motor can be driven forward or backward at any speed, optionally using a completely independent power source.

 

 

This circuit known as the H-bridge (named for its topological similarity to the letter "H") is commonly used to drive motors. In this circuit two of four transistors are selectively enabled to control current flow through a motor.

opposite pair of transistors (Transistor One and Transistor Three) is enabled, allowing current to flow through the motor. The other pair is disabled, and can be thought of as out of the circuit.

By determining which pair of transistors is enabled, current can be made to flow in either of the two directions through the motor. Because permanent-magnet motors reverse their direction of turn when the current flow is reversed, this circuit allows bidirectional control of the motor.

 

It should be clear that one would never want to enable Transistors One and Two or Transistors Three and Four simultaneously. This would cause current to flow from Power + to Power - through the transistors, and not the motors, at the maximum current-handling capacity of either the power supply or the transistors. This usually results in failure of the H-Bridge. To prevent the possibility of this failure, enable circuitry as depicted in Figure is typically used.

In this circuit, the internal inverters ensure that the vertical pairs of transistors are never enabled simultaneously. The Enable  input determines whether or not the whole circuit is operational. If this input is false, then none of the transistors are enabled, and the motor is free to coast to a stop.

By turning on the Enable input and controlling the two Direction inputs, the motor can be made to turn in either direction.

Note that if both direction inputs are the same state (either true or false) and the circuit is enabled, both terminals will be brought to the same voltage (Power + or Power - , respectively). This operation will actively brake the motor, due to a property of motors known as back emf, in which a motor that is turning generates a voltage counter to its rotation. When both terminals of the motor are brought to the same electrical potential, the back emf causes resistance to the motor's rotation.

Stepper motors

          Stepper motors are special kind of heavy duty motors having 2 or 4 coils. The motors will be stepping each time when it get the pulse.  As there are many coils in the motors we need to energize the coils in a specific sequence for the rotation of the motor. These motors are mostly used in heavy machines. The figure shown below consists of a 4 coil stepper motor and the arrow mark will rotate when the coils are energized in the sequence.

 

 

          Unlike DC motors stepper motors can be turned accurately for the given degrees.

 

Servo motors

          Servo motors unlike the stepper motor it has to be controlled by the timing signal. This motor has only one coil. It is mostly used in robots for its lightweight and low power consumption. The servo motors can also be accurately rotated by the making the control signal of the servo motor high for a specific time period. Actually the servo motor will be having 3 wires where 2 are for power supply and another one is for the control signal. Driving the servomotors is so simple that you need to make the control signal high for the specific amount of time. The width of the pulse determines the output position of the shaft

 

 

Object Detection

 

Detecting objects without whiskers doesnít require anything as sophisticated as machine vision. Some robots use RADAR or SONAR (sometimes called SODAR when used in air instead of water). An even simpler system is to use infrared light to illuminate the robotís path and determine when the light reflects off an object.The IR illuminators and detectors are readily available and inexpensive.

 

Infrared As Headlights

The infrared object detection system weíll build on the Bot is like a carís headlights in several respects. When the light from a carís headlights reflects off obstacles, your eyes detect the obstacles and your brain processes them and makes your body guide the car accordingly. We will be using infrared LEDs for headlights. They emit infrared, and in some cases, the infrared reflects off objects and bounces back in the direction of the detecter. The eyes of the Bot( mobile) are the infrared detectors. The infrared detectors send signals to the Microcontroller indicating whether or not they detect infrared reflected off an object. The brain of the Bot, the microcontroller makes decisions and operates the motors based on this sensor input.

 

 

More about IR - Detector

 

The IR detectors have built-in optical filters that allow very little light except the 980 nm infrared that we want to detect onto its internal photodiode sensor. The infrared detector also has an electronic filter that only allows signals around 38.5 kHz to pass through. In other words, the detector is only looking for infrared thatís flashing on and off 38,500 times per second.

 

This prevents common IR interference sources such as sunlight and indoor lighting. Sunlight is DC interference (0 Hz), and indoor lighting tends to flash on and off at either 100 or 120 Hz, depending on the main power source in the region where you reside. Since 120 Hz is way outside the electronic filterís 38.5 kHz band pass frequency, it is, for all practical purposes, completely ignored by the IR detectors.

 

As the receivers detects only modulated signals we need to have our IR LEDs modulated in 36 KHz to 40 KHz. We can use 555 timer to make this 40 KHz pulse. The simple circuit is given below.

IN this project  we use total tow motor so to control both the motor we require two H bridge circuit.  One for the one motor.  Microcontroller sense the signal from the decimal decoder and same output is connected to microcontroller and so on dc motor drive circuit.

 

 

Components used:

 

Item

Qty.

 ID

OPTOCOUPLER

2

IC 817

mcU

1

IC 89C2051

CRYSTAL

1

12 MHZ

CERAMIC

2

27 PF

CONNECTING WIRES

 

 

IC BASE

1

20 PIN

 

1

16 PIN

LEDS

5

RED 15 MM

REGULATOR

1

7805

CAP

1

1000 MICROFARAD

TR

2

TR548

 

2

TR 558

MICRO SWITCHES

2

PUSH TO ON

REED SENSOR

6

MAGNETIC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Planning

 

STEPS

TIME

RESPONSIBILTY

PROJECTS SELECTION

 

 

CIRCUIT AND THEORY ARRANGEMENT

 

 

CHECKING AVAILABILITY OF COMPONENTS

 

 

TESTING CIRCUIT

 

 

PCB DESIGN

 

 

COMPONENT INSERTION AND SOLDERING

 

 

TESTING

 

 

REWORK  OR TROOUBLE SHOOTING

 

 

 

Bibliography:

 

www.ludhianaprojects.com

 

www.8051projects.net

 

www.rickysworld.com

 

www.8051.com

 

 

 

 

Applications:

 

  1. used for automatic carparking in advance system
  2.  for automation in industry caryong raw material like machines, machines parts
  3. in building materil industry for carrying cement etc.