Introduction: Stalker Guard

About: I love all things related to electronics . Follow me for awesome instructables. Arduino ,linkit one, pro mini etc. familiar with these microcontrollers .

Thanks for reading mine Instructable. My name is Aditya and I live in U.P, India. Everyday we get to hear some theft

or crime in our neighbourhood. So I decided to make a device to overcome some problems . Like chain snatching , mischief with girls etc. Now without making a jalebi out of it directly coming to the point.

Stalker Guard is a device that uses an Ultrasonic sensor which detects that someone is following you or not. So now if someone tries to snatch your chain or purse so before he does u will knock him down. Their is one more feature if u are stuck in a critical situation and u want to inform someone , u can press the tactile switches on the Stalker Guard . One of them sends an emergency code to the mobile No. entered in the code and the other switch will send ur GPS Location to the same No. copy that numeric location to google maps and u get the location . Attach the Stalker Guard on the belt of the jeans or pants and its ready to go. When someone comes under ur specified distance (specified in the code) a vibration motor vibrates for 2.5 seconds and when the message (GPS location or Emergency code) is sent the motor vibrates for 0.5 seconds For better results their is an on/off button attached so if u are in a crowded area or u don't want it on , Just switch it off.

For this project I used Linkit One microcontroller as it has inbuilt GSM,GPS & Bluetooth feature (no extra shield required). You can also make it with ur Arduino.

Please forgive me for my poor English and PLEASE PLEASE PLEASE vote for me .

Here's the video ..

Step 1: Parts and Tools


  1. Linkit One(with its accessories)
  2. USB cable
  3. HC-SR04 (Ultrasonic Sensor)
  4. HC-05( bluetooth module)
  5. Sim card
  6. Vibratory motor
  7. PCB
  8. Hardboard
  9. Camera cover (or any belt pouch)
  10. SPST switch
  11. 2 Tactile switch
  12. Female pins
  13. Male pins
  14. Double sided tape


  • Soldering Iron
  • Solder Wire
  • Hot glue gun
  • Plexiglass cutter
  • Wires
  • Stapler
  • Duct tape
  • Friends Mobile

Step 2: Making the Cover

For making the cover u first need to make its skeleton because after that only u will

be able to press any switch and the skeleton will also protect any type of short circuit. I recommend you to take a cover that's bigger than the skeleton and I also recommend that u make skeleton 4 cm bigger in width than linkit one so that it and other parts slide in easily. Because I was facing difficulty in adjusting the parts of linkit One (GPS and GSM antenna and battery). Finally I ended up in removing one side of linkit one for the adjustment of parts.

Cut the hardboard with help of a the plexiglass cutter. If u don't dont have one see to any

alternative and if possible please buy it . It'll help u in future.

Step 3: Gluing the Hardboard

After cutting peices of hardboard glue them together to form a cuboid and this is our skeleton.

On completing the electronic parts . We will drill holes in the hardboard for wires. On gluing ur hardboard the glue will also take some space therefore in step 2 I suggested u to take a cover bigger than this skeleton.

Safety Measures: Before drilling wear eye protection and gloves. Make sure that u are cutting the hardboard in a well ventilated space because its small peices can cause trouble in ur respiratory system.

Step 4: Soldering the Tactile Switches and HC-SR04 Connectors

Now its show time I mean soldering time.

Take a rectangular PCB , place in the 2 tactile switches. Join two terminals with each other with a wire and solder them . This is the common +5 terminal now solder one more wire to the same terminal. Solder 2 more wires to the left over termianls which will go to AnalogRead pins of linkit one. When any tactile switch is pressed the +5 terminal will be connected to A0 &A1 pins linkit will read it with "analogRead()" function and perform further executions

As HC-SR04 can not be directly connected to linkit so we need to make connecters for it . Take 4 female pins and solder them with four outcoming wires on a small PCB.

Now at the end of every wire solder Male or female pins. lets move to the next step....

Step 5: Soldering L293D and Motor Wires

Cut 2 wires strip them from corners and solder 'em to the motor

We will use L293D to drive are motor because linkit one's signal output of digital pins is too low to drive any motor but then from where will we get that amount of voltage . Its simple we will get it from linkit one itself . Confused? linkit one's signal output is only low but it has a 5v pin on it that supplies enough voltage for motor Cut a rectangular shaped PCB and solder the L293D on it . Thereafter connect everything as follows:

1. connect and solder 1, 8, 9& 16 pins of L293D to each other they are enabler and Vcc for 2 motors

2. connect and solder 4, 5, 12& 13 pins of L293D to each other they are - or GND pins for 2 motors

3. solder 2 wires on pins 2 & 8 respectively of L293D.(these are the signal pins ).

4. solder the motor wires to pin 3 and 6 of L293D.

5. Solder 4 stripped(corner) wires to pin 16, 13, 2 and 8 of L293D.

6. Solder male or female pins on wires of pin 16, 13, 2 and 8 of L293D

Step 6: Making Common Connectors for + 5 and GND

Have a look on ur linkit one .How many +5V sockets u see ? There is only one and we need to connect 3 so how to do it.

Simple make many terminals for their connection either solder 4 female pins together or solder 4 male pins together .Now connect Tactile's, HC-SR04 and L293D's positive to linkit one. After that 1 terminal or socket will be left connect it with the +5v and every part will receive its power source Similarly do it for the gnd. Alternative: Solder all the + and - wires and connect to linkit one with their sockets respectively.

Step 7: Connections

Here are the full connections so if u missed them somewhere find them here. These connections are with respect to my code u can change them in the code

HC-SR04 :

Trig - I/O pin 8

Echo - I/O pin 10

L293D :

L293D's 2nd pin - I/O pin 7

L293D's 8th pin - I/O pin 12

Tactile Switches :



Positive terminal to +5v and Negative to GND GPS and GSM antenna's fitted in their respective sockets.

Step 8: Coding

I have made comments in the code that I think are self explanatory . But than also if u ain't getting anything please ask from me. And HC-05 was required to check the code because Linkit one doesn't prints on normal serial monitor therefore connect it with bluetooth and instead of Serial.print use Serial1.print

Some of the connections may vary that are written in the code there please refer step 7

Step 9: Adding the Power Switch

Add a SPST switch to the Li-ion battery pack. Cut one terminal of battery and connect it with SPST switch than from outside

u can on/off ur linkit one from outside.

Step 10: Drilling the Holes

Take the Skeleton and drill holes for wire, tactile switches and HC-SR04. Thereafter cut holes on the cover for HC-SR04

,Tactile switches and SPST switch wires will remain inside the cover . Make sure that u are safe while doing these task wear proper eye aid and Hancl gloves. Never keep anything bellow the drilling part (I placed all my parts and than started drilling , the drill was heavy and it banged on my linkit but by gods grace nothing happened to it) .

Step 11: Fitting Everything

Place the HC-SR04 in the wooden base and stick it with a double sided tape or(hot glue). Do the same with tactile switches. Try to fit

the motor inside the base and glue it because in mine stalker gaurd I'd forgotten to place it earlier now it looks a little ugly. Slide in the Linkit one with its GSM, GPS antenna and battery. Tape the power switch outside. Don't forget to insert ur sim. Now slide the hardboard base inside the cover. I have removed one side of my hardboard base as it was not fitting in.

Step 12: Stalker Gaurd in Use

Now its ready lets test it. Switch it on it'll take some time to set up the sim and will vibrate at starting and ready to go.

Press the tactile switch and after sending the message the motor will vibrate for 1/2 seconds. And if someone comes near to u it'll vibrate for 2.5 seconds. Its real time use video will be posted soon.

A humble request, Please vote for me and follow me for more awesome instructables.

Comment any Problem. Thank You so much !!

Sensors Contest 2016

Runner Up in the
Sensors Contest 2016