Mobile Operated Robot

cover Hello World in this post I will be showing you how to make a cellphone controlled robot .Controlling a robot using cellphone is not that complicated as your thinking it is very simple The features of this robot are

  • It have overcome the drawback of limited range and limited control. of the bot (Controlling range as large as the coverage area of the service provider)
  • No interface with other controllersThis robot can be made in two methods

1. Without using Micro controllers hence no coding required
2. Using Micro controllers (Atmega/ Arduino) which requires coding In this post I will be making the bot using the 1st method( Without Micro controllers).If you want to make in other method please like our Facebook page for the updates

NOTE :  This was a trial video taken, after the completions of the robot I have changed the appearance of the robot I have arranged all the wire and parts properly .so don’t be confused by seeing the wire and extra things in the video  🙂

Working of the Robot

The robot is controlled by a cellphone  that makes call to the cellphone phone attached to the bot while making the call .When any key is pressed control corresponding to the key pressed is heard at the other end of the call. This tone is called dual tone multi frequency tome (DTMF) robot receives this DTMF tone through the phone placed in the robot The tone is received through DTMF decoder MT8870 IC ,This IC decodes the DTMF tone in to its equivalent binary digit and this binary number is send to the motor driver L293D. which take the decision for the movement of the robot. Use the table for understanding the controls of the robot dtmf tabled

Things you need

  1. MT8870 / CM8870 / DTMF decoder IC
  2. 2 cellphone
  3. L293D Motor driver IC
  4. 3.5mm Jack
  5. 3.57Mhz Crystal
  6. Perfboard
  7. 100k, 300k,1k Resistor
  8. 0.1uf Ceramic capacitor
  9. 10uf capacitor
  10. 7805 Voltage regulator IC
  11. 9v/12v Geared motor
  12. 9v/12v Battery
  13. Chassis and Wheel for Robot


Build the circuit
Mobile operated robot circuit

Make the circuit as per the given schematics,The circuit is divided into 4 parts

  • Power supply
  • CM8870 DTMF Decoder IC connection
  • L293D Motor Driver IC connection
  • 3.5mm Jack Connection

Power supply

I am using 12v geared motor for my robot so I need 12 power supply for it but the two IC in the circuit can have only 5v supply ,so to regulate the voltage I have used 7805  IC ,Which take Input current 12V and regulates it gives an output of 5V for the IC
1. Solder the 7805 (Voltage Regulator), to the perfboard and place one 10 µF capacitor in INPUT & GND connection of IC 7805 and one more 10µF capacitor in GND & OUTPUT of 7805.
2. Take the positive supply from the battery and connect it to INPUT of IC 7805, and also connect its negative supply to GND of 7805 and you will get 5V supply from the OUTPUT pin 3. To verifying  the power flow, connect an LED to output pin via a 1K resistor voltage-regulator-7805-5v

CM8870 DTMF Decoder IC circuit
1. Solder the DTMF decoder IC on the perfboard and connect two leg of 3.57Mhz crystal to Pin 7 and 8
2. Solder a 100K resistor from Pin 3 to Pin 2 ,Take another 100K resistor and connect one end of it to            Pin 3 and end to a 0.1uf Ceramic capacitor ,Leave the connection of other end of the ceramic                    capacitor. I will discuss it in later step (3.5mm Jack Connection)
3. Solder another 0.1uf Ceramic capacitor between the PIN 17 and 18
4. Solder a 330K resistor to PIN 17 from Pin 16
5. Join Pin 1 and Pin 4 together
6. Join Pin 5, Pin 6 and  together and connect it to GND
7. Join Pin 10 and Pin 18 together and connect it OUTPUT pin of  7805   (5v) 8. The Pins 11 ,12 , 13,           14 are the output pins of the DTMF decoder which are to be connected to the            Pins 15 , 10 , 7 , 2       of the Motor driver IC L293D respectively 

L293D Motor Driver IC connection


1. Provide 5v supply to Pins 1 , 9 and 16 of L293D
2. The Pin 8 provide the voltage for the Motors so connected it INPUT of 7805 or you can provide an             external power supply for the motors by providing external power supply to the Pin 8
3. The Pins 4 , 5 , 12 , 13 are to connected to GND
4. Connect terminals of one motors to Pin 3 (Output 1) and Pin 6  (Output 2) ,and terminals of other                motor to Pin 11 and 14

3.5mm Jack Connection

There are three different layers for the 3.5mm jack say Tip,Ring,Sleeve The tip and ring is to connected to the GND .In the dtmf IC connection circuit part I have left a connection of a 0.1uf ceramic capacitor which is to be connected to the sleeve check the below pictures for more clarifications tip OLYMPUS DIGITAL CAMERA

Working Of the Robot

After complete construction ,connect 3.5mm jack to a mobile phone and turn on the auto answer mode in the call settings and enable keypad tones in the cell phone that you use to make calls. and connect 12 power supply to the circuit.Now the robot is ready for controlling through the mobile After the jack be connected to the mobile make a call to the connected the mobile on the robot Use the above table for the controls of the robot

Please feel free to ask any doubt I will try my level best in helping  🙂

33 thoughts on “Mobile Operated Robot

  1. hey,it’s really impressive what you did here,and original. most of the projects on the internet are based only on bluetooth or wifi.

    can you post a tutorial where you actually mount all of this with your hands,step by step ? i would find it very usefull

  2. Hi i worked this project with no result, it does not work when i press the button of the caller phone. but it work when i press the connected phone button to the circuit. Please help me.

  3. 300K resistor is not available . Can i use 3 100k ke resistor by using serial connection in place of single 300k Resistor
    Plz reply urgent….
    Plz plz plz

      1. 330K is available but 300K is not… Shopkeeper told that 300K Resistor not exist… So plz tell me the right suggestion… What will i do… Because this project I’ll made to represent Tata Motors,
        So, I’m afraid slightly, it’s big organization and I’m not make any kind of mistake

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