1) The document describes a mobile controlled robot that can be operated via dual-tone multi-frequency (DTMF) tones sent from a mobile phone. 2) The robot uses a DTMF receiver and decoder chip to receive and interpret DTMF tones from a calling mobile phone into digital commands. These commands are sent to a motor driver chip to control two motors and move the robot forward, backward, or change direction. 3) Operation involves calling the mobile phone attached to the robot. Pressing numbers on the calling phone's keypad generates DTMF tones that are received and translated into motor control signals by the robot.

1. A R C H A N A S
S 6 E C E
V K C E T
P A R IP A L L Y
9 / 2 8 / 2 0 1 6
DTMF MOBILE
CONTROLLED
ROBOT

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CHAPTER 1
1.1 INTRODUCTION
Controlling a robot wirelessly is possible with several methods such as Remote,
Bluetooth, Wi-Fi etc. But, the controls of these communication methods are limited to certain
areas, and complicated to design as well. To overcome these difficulties, we have come up
with a Mobile Controlled Robot.
A Mobile Controlled Robot is a mobile device, which provides wide-range of wireless
control ability to your robot unless your cell phone gets out of signal.
A general concept of mobile controlled robot is that it can be controlled from any part
of the world with just an inclusion of a camera.
Now, we like to introduce the simplest technique of fabricating a Mobile Controlled
Robot via GSM. As we have eliminated the use of a microcontroller, it could certainly help the
beginners to feel better.

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1.2 INTRODUCTION TO EXPRESSPCB
1. Open Express SCH to create a fresh schematic. The first time you start Express SCH you
will get a dialog box with a link to a quick start guide for Express SCH. This can be useful if
you want to get a general overview for the tool. Once you are ready to start, close the dialog
box to view the empty schematic.
Figure 1.1 Express SCH Start-up Window
2. Click on Op-Amp-like symbol to place components. To place the resistors, select “Passive-
Resistor” in the text box in the upper right corner.
3. Then click on the schematic for the 3 resistors (not including the photo resistor or
potentiometer) in roughly the location you want them to display. Then zoom in using the
magnifying glass tool (or the wheel on the mouse) and pan the display (using the sliding bars)
to improve your view.
4. Now you need to give each of the resistors unique identifiers. Right click on a resistor and
choose “Set component properties.” In the Component Properties box, under “Component
ID,” select “Auto Assign Part ID.” The program should assign this resistor to be R1. Set its
value 100k in the “Part Name” field and hit OK. Repeat this process to identify and label R2
(100k), and R3 (330k).
5. Rotate R3 by right clicking on it, selecting “Rotate component” and then “Body left.

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6. Now add 3 capacitor,(C1-0.4MF ),(C2 and C3-22 pF) and(C4-0.1MF) to the circuit by
first clicking back on the component placement tool (the red op-amp symbol) and using the
component names “Passive-Capacitor polarized,” IC1 MT8870, IC2 L293D Use “set
component properties” to assign , label and position (using the arrow tool) in a logical
manner.
7. Now we need to add our connections to power and ground. Let’s start with ground. Go to
the “symbol or signal label” tool, which looks like a ground, and select “Power – ground” from
the text box in the upper right.
8. Place grounds into the circuit, near pins 6,5 and 9 of the IC1 MT8870,near pins 4,5,12 and
13 of the IC2 l293D and near the bottom of the capacitor C3.
9. Repeat this process, but using “Power – Voltage Supply +5V” near pins 18 and 10 of IC1
MT8870, near pins 16,1,9 and 8 of the IC2 L293D, and power connections in at the top of
capacitor C4.
10. Now add 2 motors, where output is taken from (3and6) and (11and14) is connected to the
motors.
11. Now let’s add in our battery connection. Place a battery into the circuit, using “Misc –
Battery.” Assign the battery the part ID “B1” and give it the label “9V.” Then, use the symbol
tool to add a ground connection and a +6V network connection (this will link the positive
terminal of the battery with every other point in the circuit that should go to 9V—if you wanted
to add a switch to the circuit, you would add it between the + terminal of the battery and the
‘+9V’ symbol.
12. Now select the wire tool, and wire your circuit together. The left-click starts the wire and
sets a bend, and the right click ends a wire. After wiring, the schematic should appear as
follows.
13. Save your work, using “Save As..” to create a unique filename. 20. Check your file for net
list errors using “File” -> “Check schematic for net list errors”.

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14. Once the net list error check runs clean, you will be asked to save your file, which you
should definitely do. The final schematic should look like this.
15. Print your schematic to reference as you work on your layout. At this point, you should
review your schematic carefully to check for errors. Once you are satisfied that the schematic
is correct, close Express SCH.

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Creating the Layout in Express PCB
When doing the layout, it is particularly useful to have the actual components and or in front of
you, along with a ruler or set of callipers (the ruler and callipers are unnecessary for this
tutorial).
1. Open Express PCB. When you first open the program, a dialog box appears with links to
the Quick Start Guide and a PCB Design Tips file. If you have time, both of these links can be
instructive. Once you’re ready to continue, hit OK to go to a new file.
2. Under “File” select “New file.” Choose the 2-layer board, with Default via ‘0.056” round
via with 0.029” hole’. Change both default clearances for the filled planes to 0.05 (the
maximum allowed). Hit OK and again OK on the warning that appears in the next window.
The yellow line on the screen shows the boundary for the PCB. The default boundary is 3.8 x
2.5 inches, which matches the express PCB mini board service. This demo will use the entire
board—however for our class project you should only use half the board (1.9” x 2.5”) so that
we can double up designs. Also, be aware that no copper (pads or traces) can be placed closer
than 0.025" to the perimeter of the board.
3. The first thing you need to do is to place all of your components onto the layout. Let’s start
with the resistors. Select the component placing tool, which looks like a little IC, and from the
pull-down menu on the upper right choose “Resistor-0.25 watt (lead spacing 0.4 inch).” (This
description matches the small resistors in Ri-024). Put 3 resistors on the schematic.
4. Now double click on each of the resistors to bring up the component properties box, and
assign the resistors with part IDs R1, R2, and R3.
5. The IC1 MT8870 in 16-pin DIP package, so you place this using the component “Dip 8-
pin.” Notice how the square pad denotes pin 1. Similarly IC2 L293D in 14-pin DIP package.
6. Double-click on the component and assign the part with the part ID “U1”.
7. Now add the following components (this assumes that each of these component descriptions
match the components in the circuit—it’s good to confirm this with a ruler when you go to

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build your own circuit—matching lead spacing are particularly important). A capacitor with
the description and give it part ID, (notice how the square pad denotes the positive lead).
8. Save your work.
9. Now we need to build the components that aren’t already in the library: the motor.
10. Now (Finally!) we have all the components on the board. You can now link in the
schematic file. To do this, select “File” -> “Link schematic to PCB…”
11. Select your schematic file. You should then get a message like this:
12. Now if you select the net tool, and click on a pin, Express PCB will highlight all of the pins
that should connect to that pin. For example, select the net tool and click on the + terminal of
the battery, you should see something like this:
Click on some of the other pins to check your work and to get a sense of how the parts will
connect.
13. Now, we want to arrange our components in a logical fashion. Your goal is to minimize
the length of connecting wires. You also would like (ideally) to have a single ground plane on
the back and all of other connections on the front surface, which means that you want to avoid
having to cross wires over one another (this can’t always be avoided). To rotate a component,
right click on it and select the desired rotation. For example, here it might be nice to rotate R3.
14. Rotate the ICs and arrange the other parts until your board looks like this.
15. Now it’s time to draw in connection lines. One thing that you must consider when drawing
connector lines is the current capacity of the lines on the board. Here are some general rules of
thumb on line widths from the Express PCB web site: 0.010" 0.3 Amps 0.015" 0.4 Amps
0.020" 0.7 Amps 0.025" 1.0 Amps 0.050" 2.0 Amps 0.100" 4.0 Amps 0.150" 6.0 Amps.
Most of our circuits will not draw more than 100 mA, so any line width should be acceptable.
However, if your circuit uses a component that draws a significant current, such as a motor,
than you should err towards larger line widths. Let’s begin with the +9V lines. Use the net tool
to highlight the +9V net on your board. Then click on the wire tool and select the upper metal

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(red) layer, and a 0.1” trace width (this is overkill, but it’s a good habit to make the power lines
fat). Connect the + terminal of the battery to the top of the buzzer.
16. Now connect to the other +9V points in the circuit.
17. Now create the signal connections.
18. Complete the connections and repeat this process for the other signal nodes in the circuit.
When you get to R3, you may notice that the component would be easier to wire if it were
flipped, you can right-click on the component to accomplish this.
19. After all the signal lines are completed, your circuit should look as follows (only the
grounds are unconnected).
20. Now for the ground plane. Select the “Place a filled plane” tool, which is the green tool
right above the circle tool. Say OK to the informational message on the tool that pops up, and
then create a box that encompasses the entire circuit on the bottom layer of the chip— but
leaving a boundary of at least 0.025” from the board edge. To do this, choose the green layer
from the top bar, then click near the upper left corner of the board (at least 0.025” from both
boundaries). Click again near the upper right corner…at this point your display looks
something like this.
21. Continue down to the bottom right corner and then to the bottom left corner. Then right-
click to end the box. Your display should now look like this. Notice how there is a space
around each pad in the layer. The width of that space is controlled by Board Properties, under
the “Layout” menu, and we set that at the largest possible size when we started this process (in
step 2).
22. Now we need to make our ground connections. Use the network tool to highlight the
ground connections. Right-click on the ground pad for the battery. Select “Bottom layer pad
shape” and then “Thermal pad to filled plane.” This will link that pad to the ground plane.
The thermal pad has some thermal isolation between it and the rest of the plane, which will
make it easier to solder later.

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23. Repeat this for all of the ground pads in your layout. Your layout should now look like
this.
24. For your own circuit, you should also add your initials in an unused corner of the chip. Do
these initials in the top metal (red) layer rather than in the silkscreen (yellow) layer, because if
we use mini-boards, the silkscreen layer is not included. To add text, select the text tool, select
the layer where you want the text to appear, and enter the text in the box on the upper right.
Then click on the layout to place the text.
25. Carefully inspect your circuit board. Use the layer visibility tools in the bottom left corner
to turn off and on layers. Zoom in to check for connections. Highlight all of the pads with the
network tool on to verify that they are correctly connected. Print out your circuit and confirm
that every connection specified in the schematic is present. With circuit boards, you definitely
want to measure twice and cut once.

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CHAPTER 2
CIRCUIT DIAGRAM & WORKING
2.1 BLOCK DIAGRAM
Figure 2.1 – Block Diagram

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BLOCKDIAGRAM DESCRIPTION
Block diagram consist of 2 sections
a) Transmitter section
b) Receiver section
Transmitter section contains only cell phone.
Receiver section contains 3 stages,
1. Cell phone
2. DTMF section
3. Motor driver
Cell phone is used to give instruction to the robot by pressing the keypad of the cell
phone. The output of this section is dual tone frequency which is received by the DTMF
receiver.
DTMF section is used to receive the dual tone coming from the cell phone and to
convert it into digital numbers by using decoder IC. Here MT8870 decoder IC is used. This IC
detects and decoder 16 DTMF tones into 4bit output.
Driver stage contains motor driver and 2 motors. The decoder output from the decoder
IC is applied to the driver IC. Here L293D driver IC is used. It is used for driving motors.
According to the incoming signal motor change its direction

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2.2 CIRCUIT DIAGRAM
2.3 CIRCUIT COMPONENTS
Components Quantity
Resistors
100k
330k
2
1
Capacitors
22pF
0.1uF
0.47uF
2
1
1
Crystal Oscillator
3.57MHz 1
ICs
MT8870
L293D
1
1
DC Geared motor 6v
SLA Battery 5v
2
2
Table 2.1 circuit component

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2.4 CIRCUIT OPERATION
In mobile controlled robot ,we use two mobile phones.This robot is controlled by a
moble phone that makes a call to another mobile phone attached to the robot.When the user
calls the mobile which is mounted on the robot the call is received by auto –answer mode. In
the course of a call, if any button is pressed, a tone corresponding to the button pressed is
heared at the other end of the call.
Figure 2.3 – DTMF keypad
This tone is called “ Dual Tone Multi Frequency ( DTMF)” tone.The robot receives this
DTMF tone with the help of headphone attached to the robot.The received tone is processed by
the DTMF Decoder IC ,and then transmits the signal to the motor driver IC to operate the
motors.
The motor driver L293D can control 2 motors bi-directionally and has 4 inputs.The 4
outputs from the decoder IC is fed into the 4 inputs of the motor driver directly .Now , call will
be in progress between first and second mobile phones.

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Take the keypad in the first mobile phone and press the numbers. If ‘1’ is pressed ,one
motor will rotate in a direction .If ‘2’ is pressed ,that motor will rotate in opposite direction.If
’3’ is pressed motor will stop rotation .Press ‘4’ and ‘8’ for rotating the other motor.Now press
‘5’ so that the robot starts moving forward.While pressing ‘0’ robot moves backward.
Table 2.2 DTMF Binary output
If the button pressed from mobile is ‘1’, it gives a decoded output of ‘0001’. Thus
motor connected to the first two pins will get 0 volts and second motor will have 5 volts to one
pin and 0 volts to the another pin. Thus second motor starts rotating and first motor is off. So,
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.

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CHAPTER 3
3.1 PCB DESIGN
Figure 3.1 – PCB Layout

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3.2COMPONENTS LAYER
Figure 3.2 – Components layer

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CHAPTER 4
RESULT
The mini project ‘DTMF mobile controlled robot’ is successfully completed. As the key
pressed on the mobile phone, the motor will turn clockwise or anticlockwise direction, left,
right, forward, backward.
Figure 4.1 - Prototype

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CHAAPTER 5
ADVANTAGESAND DISADVANTAGES
Advantages
 This robot can be virtually controlled anywhere from the world.
 Easy to set up.
 No microcontroller and no tough coding.
Disadvantages
 Requires a camera to manoeuvre your house or office when you are far away
from the robot.
 Call charges will be deducted according to the service provider plans when
you control the robot.

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CHAPTER 6
APPLICATIONS
 Can be use in military for disposing land mines.
 Best suit for search and rescue operations.
 Addition of wireless camera helps to acess this robot from any part of the world to
monitor your house or office.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.
 DTMF robot with slight modifications can be used in industrial applications.

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CHAPTER 7
CONCLUSIONS
Cell phone operated robot is a robot whose movement can be controlled by the
pressing the number of the cell phone. The property of robot to operate by the cell phone helps
you to operate the robot from some distance. The benefit is that we can operate this robot by
using any cell phone with the working range as large as the coverage area of the service
provider.

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REFERENCES
 www.wikipedia.com
 www.electronicshub.com
 www.google.com
 E Magazine

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APPENTIX

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DATA SHEETS

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