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Multitasking Robot



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.

Autopath Robot


We control the robot using GSM.

In this project we use 89c2051 microcontroller as a main processor. We use this processor to run the vehicle. This controller is basically a  20 pin ic. In this project we use two sensor also. These sensor are connected to the port p3.4 and port p3.5





Pin no 20 is connected to the positive supply. In this project we provide a 5 volt dc power supply. This power supply is truly regulated power supply. Pin no 10 is connected to the negative supply. Here we supply a negative voltage on this pin. Crystal is connected to the pin no 4 and 5 of the microcontroller. Crystal provide a clock signal to run the vehicle and process all the internal requirement of the circuit. We use two sensor and these two sensor are connected to the p3.4 and p3.5 of the microcontroller.  Infra red led is directly connected to the power supply. For the regulated power supply we use ic 7805 as a regulator to provide a fix 5 volt power supply. IR sensor play major role for antifalling and autopath. In antifalling we will use one IR sensor which will sense surface if found, continue to move. If surface not found then move back.

IR sensor for autpath- we used Two sets of IR sensors-one for left direction and one for right direction. In IR set one is Transmitter and another is receiver. Transmitter transmit ir frequencies, when IR receiver  receives IR frequency then it give low signal to Microntroller. When IR sensor give signal to microntroller then it take action according to input sensor.

Motor drive circuit-For the safety of the main processor we interface the motor with optocoupler circuit. Here we use pc 817 ( 4 pin opto coupler) to interface the micro controller with  the motor circuit. We use H bridge circuit with the motor. H bridge basically control the movement of the motor. With the help of this H bridge we change the direction of the motor. We use four transistor circuit with each motor. We are using four transistor circuit. Out of these four transistor  two transistor is NPN and two transistor and PNP transistor.  One NPN and One PNP provide a one direction voltage and motor moves on one direction. Second NPN and second PNP transistor again change the direction of the motor automatically. If right side sensor detect the signal that there is wall in front of sensors then it turns the sensor left and similarly if left sensor find the wall then it turns the robot towards right. We will use two motors in this project. Two motors help us to move motors right and left. one motor work at a time to move robot right and left.


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




























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.




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.




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



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 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.




IC 8870(1)


IC 74154 (1)




PC 817(4)


CRYSTAL ( 3.58 Mhz), (12 MhZ)










470 OHM(4)


4.7 K OHM (4)


1 K OHM (4)


22K OHM (2)

100 K (1)

10 K(4)




10 mfd(1), .

1mfd(104) (2),




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.



1.to control antennas.

2. to control machines where manpower cant be used

3. for machines automation


Cant work at large temperature area.

Have no feedback for any action


Low cost

Large range

Easy to implement