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Cellphone Operated Land Rover (Robot)



Why do we need the diode in above circuit???



Mail me at

How to burn the given program in the ic atmega16? Please tell me all the steps... Please help me...

my dtmf part of this circuit is not performinng well.all leds connected to dtmf output are glowing.they do not changing their status .what may be the problems.Plz give some solutions.


hello sanjay....


this type of problem is occure when dtmf decoder not receive proper tone from handsfree set of mobile so first you have to check that your handsfree give proper output as it should give.......!!! check it on oscilloscope.


after checking give it to dtmf decoder i hope after that it will give output in proper manner....


if after that it not work than you will tell me about it.

actually am facing that problem too ... my decoder circuit could not be able to detect from a mobile phone (may be beacuse there was too much of noise ..) should i have to change the value of capacitor (0.47 uf??) i have tried using a dtmf encoding software and it works pretty fine with it... 


tell me how to rectify this problem ? do i need to change any electronic circuitory for that?? 

thanks in advance,,!

why NOT gate ic is used???

nice project

The output if 8870 dosent seem to be TTL compitable..

That is you cannot connect it directly to a device running with TTL Logic.

Thats the reason we will be using a Inverter.

The advantage of it is that it can ve used to convert Non TTL to Transistor Transistor logic.

Great project indeed.


i have uploaded the dtmf ckt image above.And i need to know that can i use yhis ckt and fed its output directly to the 8051 without inverting the inverter necessary


hi dipak


your question is that can you use dtmf interfacing with controller with out using invertor gate...???


answers is that when you operated dtmf for led blanking at that time it is not require invertor gate because we use invertor gate to make MT8870 logic match with microcontroller which is working on TTL logic so...


at a time led interface it is not require....


thank you.

without using not gate does any output shows on leds...?? or not..?

I find this cellphone operated land rover robot very useful.

My apologies.. I recently posted that the reason for the inverter is 8870 is not TL compatable.. I was wrong.. It will work just fine without an inverter.. If you observe the decoded output closely.. The LSB is at the bottom whre as the MSB os at the top but where as in a micro controller the LSB is at the top and the MSB at the bottom.. This will cause complicated connections.. For simplicity in the code and connections the inveter is used..

We can do this without the inverter by directly connecting the decoder to the controller but we should write the code properly..


like.. 1= 1000 not 0001 (Without the inverter)

My HT8870 get heated when i connect the power supply....


Why this happen can u please tell me Sir...


Thank you.00

you should have to check proper connection of IC as well as supply voltage is same as data sheet specified require to proper operation..


thank you.

can we do this project with ATMEGA-8....

if can do plz send me code and changes of schematics...

you can do it with any microcontroller. only changes you need to make in programming is change the port no. as you choose for ATMEGA8. also..instead of #include<mega16.h> you need to write #include<avr/io.h>. it will work with most avr series microcontroller.

where cell phone input is coming tip or ring   plz tell 

you can obtain it from handfree of cellphone. see fig on this page...                                                                                                                              

so should the sleeve be kept unconnected??

Hi I am a student and I am working with this project. But i can not decode DTMF signal. Because when i cut headphone wire I see that there are three colored wire GOLDEN, BLUE and RED.  can not identify the RING and TIP wire. Please Please Please  give me some advice or circuit diagram that I can connect RING and TIP to MT8870 DTMF decoder IC. And also actually where I cut the headphone wire after MIC or before the MIC. Please Please Please  give me some advice. I want to complete my project.

Please mail or contact me:


ring and tip signal you can obtain from probs of handsfree of mobile phone in which ring signal is ground and tip is apply to circuit as mention above..




1. Sleeve: usually ground
2. Ring: Right-hand channel for stereo signals, negative phase for balanced mono signals, power supply for power-requiring mono signal sources
3. Tip: Left-hand channel for stereo signals, positive phase for balanced mono signals, signal line for unbalanced mono signals
4. Insulating rings

1) Sir, in the above circuit diagram of the "cellphone operated land rover robot" project , you have given details of controlling 2 dc motors. 


2) In my project , i want to control 12 dc motors(6 at a time)  using the same circuit as you have given. so i want to know whether it is possible with same number of ports in microcontroller. if possible which ports can i use to connect to L293D and control the 12 dc motors(6 at a time).?


hello santhosh..


your question is that how you can control 12 motor (6 at a time).....


i think you are working on robot which has 6 motor one side and other 6 at another side. now if you want to control these motor you not need to change in port or other things. you just use RELAY interface with microcontroller instead of driver ic L293D and control relays using microcontroller so this relay provide power for all 6 motor by switching machanisum.


for how to interface RELAY you just refer my website link which give you total imformation for relay interfacing....


link is below


thank you.

can anyone give me the code for P89V51RD2....?


plz mail it to


 hi sir , santhosh here,


 1) i have doubt in your code for right and left turns


It is given as 

                   0x85= for left turn

                   0x8A=for right turn


But i think its the other way round i.e


                   0x85= for right turn

                   0x8A= for left turn


Please verify and reply me as early as possible.



thank you sir              

sir i need a code in c program

porated relay sms controll max232 , m89s51 and uln2803

+circuit daigram



If my robot has 4 motors of 12V , 200 rpm then what should be the battery specification???

Will it run if I use a12 V battery???

I mean other ICs like not gate IC and ATMEGA16 wont be affected???


Measuring energy for your battery can be done with an equation. The equation consists of dividing the capacity by your actual load current. This will give you the hours of life of the battery. A circuit that can draw 10 amps that is powered by a 9v rectangular battery can last for about fifty hours.

before connecting higher voltage than 6v you should connect regulated ics like 7805 , 7806 , 7812....ETC.



I want to do this project as my final project with some extension.what extention can i make to this circuit


It is already extended version of mobile phone technology.... !!!

it is a nice project.. i have doubt why u using 3.57 crystal oscillator  .. if we put any other oscillator wat change will hap pls rep as soon.........



A 3.579545 MHz crystal connected between pins OSC1 and OSC2
completes the internal oscillator circuit. any closer value is okay ..but errors will creep in as the value you put is the clock frequency to all the internal algorithms embedded for detection of frequencies, calculating the durations and giving outputs...hence changing the clock value can lead to lot of errors and eventually undesired outputs will come.. 

can we use pic16f877 instead of at mega 16 pls reply

you can use any microcontroller which has minimum two ports..


also i want to ask one question that you have any problem with ATMEGA16.....??



sir m workin on this project....can u tell me how to make it work on 4motors instead of two........nd one more thing....the same project was made by one of myfrnd in his college...his car dnt had much speed when it is in motion...i saw sum project on youtube which in which the car speed is quite good as compared to what i saw............
sooo what should we do to provide more speed for this car......thanku

To get more speed of robot you does not need to attach two more motor. it provide more torque or pressure to move but at same time it will consume more power from battery..nd there is no change in speed.


to increse speed use high RPM motor.


also remember one thing that as rpm increse in gear motor torque will reduce..!!




why are the resistors R4 to R8 are used??? i guess the circuit works fine without them??? reply please!!

I have d same doubt...... Did u check the output without using the resistors????? Is it working properly?


why don't we use 8051 series  instead of using avr controller


yes you can use 8051 for control robot but AVR microcontroller is ultra low power microcontroller and in portabel application it is most issue...



I m finding a lot of problem in operating the above circuit....... m working exactly on the same circuit as shown on this site....

m gettng the bit patterns from decoder on passing DTMF tones.... bt i m not gettng the output from ATMEGA 16

the voltage is not sufficient to drive the 4 motors.... i.e 2 on one side and 2 on other side together............ i have not connected relay yet.... should I connect??? if yes then how many relays would b needed to drive 4 motors(as specified above)????????


Is it necessary to connect the resistors R4,R5,R6,R7?? what is their function in this circuit???


I seriously need help as soon as possible..... This project is very important for me to be in running condition perfectly in a week...........



Please do help me Sir..............


Thank You

okay... first of all i will answer to your question why those resistors are connected : well i guess they are connected to make sure that the microcontroller pins won't get  any high currents from the battery source.. they are really not necessary though .. but not for the reset pin beacuse reset pin needs to be high  (or logic 1) to be in off condition for atmega 16 (and atmega 8 too i guess)..



you aren't getting the output ? how are you saying that? have u checked it by a multimeter?

make sure to know where is the problem arising from..


and 4 motors? there were only 2 motors specified above..and why do you want to use a relay? 



hi... i am working on this project. can anyone help me out with this problem of mine..?

my problem is that the output of the not gate i.c is not inverting...

but if i check the i.c seperatelly the output is inverting.

why the output must be not changing in the circuit can anyone tell me please..?

its urgent.


Hey santosh im from ssec bhavnagar,

plz give me your mobile no on my mail id 

mare programing mate thodu kam 6e...

sir,when i connect the power supply to the circuit the motor moves forward although the tip and ring is not connected to the mobile phone.can u suggest me where is the problem???????

sir.. i want the code for atmega16..pls mail me

sir pls.. rply

problem with the code in compiling to generate hex file

always getting error in header filess


pls. tell me the whole procedure for compiling and generating hex file


require to make project whole project is ready only need to burn the controller pls...

tell me the compiler needed...
pls.... sir need urgently pls...