Mobile Operated Robot

Hello, everyone in the cool DIY hacking tutorial i will be showing you how control your robot with your mobile phone in a simple way.

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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).

Watch the robot in action !!!

Working of the Robot

The robot is controlled by a cellphone that makes call to the cell 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

  • 1 × MT8870 / CM8870 DTMF decoder IC Both CM8870 or MT8870 IC will work
  • 2 × cellphone One will kept on the robot and other will be used as remote
  • 1 × L293D Motor driver IC
  • 1 × 3.5mm Jack
  • 1 × 3.57Mhz Crystal

View all 14 components

  • 1
    Step 1

    Make the receiver

    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 resistorvoltage-regulator-7805-5v

  • 2
    Step 2

    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 toGND
    7. Join Pin 10 and Pin 18 together and connect itOUTPUT 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
    Step 3

    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


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