DTMF Controlled Robot without Microcontroller

In this project, I will show you how to design a simple Robotic vehicle that can be controlled using a phone. The project is called DTMF Controlled Robot without Microcontroller.

Introduction

DTMF is an acronym for Dual Tone Modulation Frequency. Robotic vehicle based on DTMF technology is explained in this article. Here, is a circuit that operates the robot without using a microcontroller. This circuit consists of simple DTMF Tone decoder IC and a motor driver IC.

DTMF Controlled Robot without Microcontroller Image 2

When a key is pressed from our mobile, it generates a tone, which is a combination of two frequencies. Of the two frequencies, one is high frequency and another one is low frequency. This frequency can be decoded by the decoder IC into binary sequence. Using this binary sequence, the robot is controlled.

DTMF Based Robotic Vehicle Circuit Principle

DTMF based robotic vehicle circuit consists of DTMF Decoder IC, Motor Driver IC (L293D or L298N), motors and a simple robot chassis to hold all these components.

DTMF decoder IC used is HT9170B (actually a variant called CM8870 is used but the functionality is the same). It has 18 pins. Tone from DTMF encoder is given to the DTMF decoder IC. The decoder IC internally, consists of operational amplifier, whose output is given to pre filters to separate low and high frequencies. Then it is passed to code detector circuit and it decodes the incoming tone into 4bits of binary data. This data at the output is directly given to the driver IC to drive the two motors. These motors rotate according to the decoded output.

The following image shows the binary decoded output corresponding to the key pressed on the keypad.

DTMF Decoded Frequency Output Table

Also Read the Related Post: Simple Line Follower Robot using Microcontroller

If the button pressed from mobile is ‘8’, it gives a decoded output of ‘1000’ (in the order of Q1, Q2, Q3 and Q4). Thus motor connected to the first two pins (OUT1 and OUT2) will rotate and the second motor stays off. So, the robot moves in one direction either to left or right. If the robot is to rotate forward or backward then the binary value should be either ‘0101’ or ‘1010’. These values indicate that two motors rotates in the same direction i.e. either forward or backward. The above table gives the low frequency, high frequency and binary output value of each button pressed in the keypad.

Circuit Diagram of DTMF Controlled Robot without Microcontroller

DTMF Controlled Robot without Microcontroller Circuit Diagram

Circuit Components

  • DTMF Decoder IC (HT9170B or CM8870)
  • Motor Driver IC (L293D or L298N)
  • Motors
  • Resistors – 100KΩ x 2, 330KΩ
  • Capacitors – 100nF x 2, 22pF x 2 
  • Crystal – 3.58MHz
  • Robot Chassis
  • Batteries

NOTE

  • As mentioned earlier, the DTMF Decoder IC used here is CM8870. But the circuit diagram mentiones the DTMF Decoder IC as HT9170B. Since the pins are same, there won’t be any problem. But please refer to the datasheet.
  • Also, the circuit diagram mentions the Motor Driver as L293D but the motor driver used here is L298N. Please refer the datasheet for pin diagram.

DTMF Controlled Robot without Microcontroller Image 1

DTMF Controlled Robot Circuit Design

The main components of the circuit are DTMF decoder IC, motor driver IC and motors. The decoder IC used here is CM8870 IC. The second pin of decoder IC is an inverting pin of the operational amplifier.

Tone is applied to the IC through a series of capacitor and resistor. The output of the Op Amp is feed back through GS pin of the IC. An external crystal is connected to the 7th and 8th pins of the IC.

Motor driver IC used is L298N. It has 15 pins. If you are using a Module, then connect the Outputs from the decoder IC to IN1, IN2, IN3 and IN4. The motors are connected to OUT1, OUT2, and OUT3, OUT4.

Related Post: Remote Operated Spy Robot Circuit

How to operate DTMF based Robotic Vehicle?

  • Arrange the robot mechanically i.e. connect the wheels to the motors, place the circuit on the robot with a mobile fixed to it.
  • Now press ‘5’ from your mobile, robot starts moving forward.
  • Now press ‘0’ from your mobile, robot starts moving backward.
  • Now press ‘2’ to rotate the robot in left direction.
  • Now press ‘8’ to rotate the robot in right direction.

DTMF Controlled Robotic Vehicle Circuit Applications

  • DTMF robot with slight modifications can be used in industrial applications.
  • DTMF robot with human detector sensor can be used at the time of disasters like earth quake to detect the human under buildings.
  • DTMF robot with camera can be used in surveillance systems.

Limitations of DTMF Controlled Robotic Vehicle

  • DTMF robot may not work properly if it is operated with another mobile when there is no signal.
  • Mobiles with particular jacks are only used.

88 Responses

  1. Hello Sir,
    I am currently in third year of electronics and telecommunication. For my mini project, i want to make this. can you please provide me with the necessary details like coding etc. That will be of very much help. You can send me details on my email id gauravdhangar91@gmail.com. Thank you.

    1. here coding not required ,as it it is pre programmed, you need to give the connections according to the circuit diagram.

  2. Hello Sir,
    I am currently in third year of electronics and telecommunication. For my mini project, i want to make this. can you please provide me with the necessary details. That will be of very much help. You can send me details on my email id madhuri143bhosale@gmail.com. Thank you.

  3. Hey Admin,

    I really appreciate your project and thank you very for the detailed explanation. It helped me a lot. However, I am currently working on DTMF Controlled Robot ‘WITH’ Microcontroller. So, If you have a similar analysis, could you please share?

    Also, I am looking for applications of dtmf based moving robot for industrial monitoring (using microcontroller).

    Any info regarding the subject would be of great help.

    Even if anybody else has any info, please mail me. Thanks in advance!

    My email id: haritha.padala124@gmail.com

  4. Hello Sir,
    I am currently in third year of electronics and telecommunication. For my mini project, i want to make this. can you please provide me with the necessary schematic digram of dtmf decoder circuit,and i am also varying the speed of motor using pic4550 controller that is decoded output is given to the pic and then driver ic,so i want schematic diagram and some synopsis of the project,that will too much help me. That will be of very much help. You can send me details on my email id ajagtap8020@gmail.com. Thank you.

  5. Hello Sir,
    I am currently in third year of electronics and
    telecommunication. For my mini project, i want to make
    this. can you please provide me with the necessary details
    like coding etc. I also wants to know how it works and which components are used with their ratings and all the necessary details in brief description. That will be of very helpful for me.
    You can send this information to my email id
    mool.anjali5@gmail.com
    Thanking you in advance.

  6. Hello Sir,
    I am currently in third year of electronics and
    telecommunication. For my mini project, i want to make
    this. can you please provide me with the necessary details
    like coding etc. And I also wants to know how it works and which components are used with their ratings and all the necessary details of this project. That will be of very helpful for me. You can send this information to my email address
    mool.anjali5@gmail.com

      1. what happened if i dont use it . so that i will come to know the importance of it .. I dont know much about osc

  7. Hello, could you please help me out? Are those electrollitical o dielectrical capacitors!? What happens with the common wire of the tone!?

  8. to move this robot in a certain direction,do we have to keep pressing the certain button .plz plz reply me.thnx

    1. No…once the input is received from the phone…robot will be in that state until next input is received

  9. Hello i am 3rd year engineering students i will implement the DTMF based robotic control without using microcontroller project using the Ckt diagram which shown in electronics hub site but i will confused what i should give to input an antenna or mobile. The video given below whose Ckt is very different than Ckt diagram. Plz help me give me full details as soon as possible.

    1. Here audio jack is connected to the mobile…Please follow the circuit diagram for conenctions…In the video we have used PCB boards..But the circuit is same

  10. can we use 9V battery instead of 5V ?please reply me ii have to complete this project in very short time.
    thanks

  11. i am working on this project.i inserted leds on four inputs with resistances.but all leds are glowing even dtmf input isnt given to it.
    plz guide me i have to complete project.
    tthnx

    1. Mobile is connected using mobile jack…Two wires(ring , tip) of the jack are connected to DTMF IC

  12. Dear sir,
    Can we add infrared sensor nd proximity sensor in dtmf controlled robot. If yes, plz give a suggestion…
    Thank you

    1. In this project simply the direction of the robot are controlled using DTMF technology. Explain clearly about requirements of your project.So that we can help you..

      1. Hi, we are going to make this for our project. May i know the voltage value of the 100nf and 22pf capacitors? We can’t find those valtage value in the article, thank you in advance. ?

  13. Hi sir , how much is the cost of this circuit ? con you help me about the hardware and code of this circuit
    i well select it as a final project so i need to your help
    Thanks a lot

  14. hello
    i am impressed with ur project where i can fid further details of it and i nedd cost estimated for ics

  15. Hi I’m ece final year student, I’m thinking to do dtmf controlled robotic, send please details, cost ,

  16. hey,
    you have used BO motor or geared motor? Of how much rpm and operating voltage? And what is value of crystal?
    Please help.

    1. Hi, we have used a geared motor of 150RPM and an operating voltage of 5V. The crystal used for DTMF Decoder IC is 3.579545MHz.

  17. Sir,
    I have a problem in this project the robo is not moving straitly it moving in circular so i checked the motor inputs it is not giving equal voltages to the each motor what will we do pls tell us sir

  18. Great. Very effective and interesting project for electronics lover.
    This decoder ic can be used to operate other electrical appliance by DTMF if the connecting the relays.
    Thank u so much

  19. Hi,

    I’m trying to simulate this project on Proteus but can’t find the DTMF decoder HT9170B or anything similar. Could you please tell me how you did it?

    thanks in advance

  20. Hello Sir,
    I am currently in third year of electronics and telecommunication. For my mini project, i want to make this. can you please provide me with the necessary details. That will be of very much help. You can send me details on my email id

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