Introduction: How to Make Mobile Controlled Car

Picture of How to Make Mobile Controlled Car

Designed a Toy car that is controlled by a Mobile phone.

This Project implements the functionality of IVRS (Interactive Voice Response System) technology.

The car is controlled by a Mobile phone that makes a call to the phone attached to the Car. During the call, if any key is pressed, a DTMF (Dual Tone Multi Frequency) tone corresponding to the key is sent at the other end.

The received tone is processed by the Atmega16 microcontroller with the help of MT8870 DTMF decoder.

The decoder converts the tone into an equivalent binary code before sending it to the controller. The controller is pre-programmed to take a decision for any input and, outputs its decision to the motor driver that drives the car in various directions.

Using mobile phone to control the car helps overcoming the limitations of Range (a problem faced with RF systems).

Note: Interactive voice response (IVR) is a technology that allows a computer to interact with humans through the use of voice and DTMF tones input via keypad.
This project is an inspiration from the July 2008 issue of Electronics For You Magazine...!

Step 1: Tools Required

Picture of Tools Required

1. Soldering Iron

2. Solder wire and Flux

3. Power / Hand Drill machine

4. Multimeter

5. Screw Driver

6. Cutter Knife

Step 2: Components Needed

Picture of Components Needed

General Purpose PCB

7805v Regulator

MT8870 DTMF Decoder

ATmega16 AVR Microcontroller

L293D Motor Driver

74LS04 NOT gate

1N4007 Rectifier diode

Resistors (¼-watt):

100-k.ohm --------------------------------------------------------x 2

330-k.ohm --------------------------------------------------------x 1

10-K.ohm ---------------------------------------------------------x 5

100-ohm ----------------------------------------------------------x 4


0.1μF ceramic disk ---------------------------------------------x 2

22pF ceramic disk ----------------------------------------------x 4

10uf, 100uf Electrolytic Cap ---------------------------------x 2


Old Earphones

Male and Female Header Pins

XTAL1 - 3.57MHz crystal

XTAL2 - 12MHz crystal

S1 - Push-to-on switch

6V, 50 RPM geared DC motor with mount ---------------x 2

Toy Car wheels -------------------------------------------------x 4

Battery - 6v, 4.5Ah

LED - 3mm (Any colour) --------------------------------------x 5

Old Plastic Pen or Straw

2" Nut and bolt --------------------------------------------------x 4

Step 3: Soldering Components

Picture of Soldering Components

1. Start By soldering the ATmega16 Microcontroller and carefully place other components on the General Purpose PCB according to the schematics.

2. Solder them carefully according to the schematics.

In addition to the schematics, i designed 5v regulated power supply for the controller using 7805 voltage regulator IC. As long as Battery voltage is in range of microcontroller, there is no need for voltage control. In case of using batteries above 6v, use 7805 voltage regulator.

3. You will need to do track soldering in order to adjust the Circuit on a small PCB.

4. You can also make a PCB layout and develop a professional PCB.

Step 4: Preparing Phone Connection Cable

Picture of Preparing Phone Connection Cable

1. Cut an old Earphone at a distance of about 12" from the 3.5mm Audio connector.

2. Carefully Strip the insulated wire.

3. There will be two pairs of wires inside:

(i) Red - Gold

(ii) Blue - Gold

Note: These colour combinations vary with various Brands and Region.

4. Join the same coloured wires with each other or eliminate them (We don't require those). We only need two different coloured wires, one is Ring and other is Tip.

5. Remove the Red and Blue insulated coating from both the wires and solder them on a 2-Pin male Header.

6. You can also use Heat shrink tube to secure the connection of wires.

7. Check the connections using a multimeter and identify the Ring and Tip of the connector.

8. The two pin header will be connected on Circuit Board and 3.5 mm Audio pin on other side will be used to connect a Mobile Phone.

Step 5: Software for Atmega16

1. The software is written in C language.

2. I used AVR studio to write and compile the code. The code is very simple to understand and uses only basic functionality of the controller.

3. The Code text file and Hex are provided for reference.

4. Use any AVR burner to burn the provided Hex file into the controller.

Step 6: Connect the Peripherals

Picture of Connect the Peripherals

  1. Drill holes for the Motor mounts on the edge of the circuit Board.
  2. Mount the two DC motors and the Wheels.
  3. On the front side, use any iron rode or a thin pencil as Axle to attach Wheels.
  4. Connect the mobile phone using the prepared earphone cable in step 4
  5. Set Mobile in Auto-answer mode while connected with earphone cable.
  6. Connect the battery, switch ON and verify the circuit. If everything went well, the front four LEDs should light up.

Step 7: Operating Car

1. Make a call from a Mobile phone to the phone connected to the Car.

2. As said earlier, this project uses the IVRS technology for controlling the car. A corresponding DTMF tone is sent for each key Press.

Press Key 2 - Move Forward

Press Key 8 - Move Backward

Press Key 5 - Stop

Press Key 4 - Turn Left

Press Key 6 - Turn Right

Note: Disconnect the call and remove the battery when not using the Toy car.

Step 8: Making Car Roof and Finalising the Design

Picture of Making Car Roof and Finalising the Design

We will now give our car an attractive look and design its roof, that will also act as platform for placing the Mobile Phone.

  1. Cut a PCB upto the required size of Roof.
  2. Drill Holes along the corners and corresponding holes on the circuit board.
  3. Cut an old pen or a straw in four equal pieces and using 2" nut - bolts attach the roof above the circuit board to give the car an attractive look.

All The Best...Have Fun..!!


nihal18coc (author)2017-11-17

how to burn file in ic if i will not burn file what will happen no file is burn in it

Techgenie (author)nihal18coc2017-11-19

To upload the program to the microcontroller, you need a programmer device.

That device will be used to connect to the microcontroller IC and then the code will be burnt to it.

If no code is uploaded to the IC, the project will not work.

SourabhB11 (author)2017-07-22

can you please tell me how to burn our program
how to connect usbasp
i am new pls

MohammedS197 (author)2017-03-20

what are the applications?

DrewS59 (author)2017-03-06

is there any alternative for ATmega16? ATmega8-16PU is the available here in our country .
and can we use Ultrasonic Sensor as an alternative to MT8870 DTMF Decoder? newbie here . Thanks

Techgenie (author)DrewS592017-03-06

You can use ATmega 32 as an alternative. Also, you can use ATmega 8 with this car but you will have to re- write the code for the microcontroller. However, with ultrasonic sensors & suitable code, this car can only avoid obstacles and it will lose the functionality of being controlled by a mobile phone.

DrewS59 (author)Techgenie2017-03-08

Thanks for the help sir :)
We have the decoder and we used PIC16 instead of ATmega16 . Our prof said that the PIC and ATmega are both same

Revathy_T (author)2016-07-11

What is the size of the general purpose pcb board

AnshP1 (author)2016-07-07

can i use electrolytic cap 0.1 uf capacitor rather than ceramic disk

Techgenie (author)AnshP12016-07-07

No, an electrolytic cap is always used between the Vcc and Gnd, but it is not the case here. So, only a ceramic cap will work.

AnshP1 (author)2016-07-06

i did not understand what is 0.47 uf capacitor because it is not listed in the parts needed

Techgenie (author)AnshP12016-07-06

Actually i could not get a 0.47 uf ceramic capacitor, so instead of that used a 0.1 uf ceramic capacitor and it worked well.

AnshP1 (author)Techgenie2016-07-07

Thanks a lot

sam David (author)2015-09-28

prathi5 (author)2015-08-23

well i m trying it now. i bought all the components required. hope it works :)

Techgenie (author)prathi52015-08-23

Great..! It will definitely work very well, just ensure proper connection between the components.

All The Best..!

vijjusri14 (author)2015-08-19

I made this 4 years ago Inspired from EFY

Techgenie (author)vijjusri142015-08-19

It would have been real fun..:)

vijjusri14 (author)Techgenie2015-08-19

Yes it is! that was my first project with my own PCB, before that I used to make my projects on pref boards which ate too messy!!

Techgenie (author)vijjusri142015-08-23

Nice..! Did You make an instructable as well ?

sezgingul (author)2015-08-17

really successful!

Techgenie (author)sezgingul2015-08-17


Saiyam (author)2015-08-17

Very well made!

Techgenie (author)Saiyam2015-08-17


About This Instructable




Bio: Hello Guys, I am techgenie, an Electronics hobbyists, tech tinker and developer. I dedicate my free time in designing and making various creative and innovative ... More »
More by Techgenie:How to Make a Mobile PowerBankHow to Make 18650 Battery Holder at HomeLED Night Light
Add instructable to: