Car Alarm With Bluetooth and RF Remote




This project is about the construction of a car alarm with remote control and Bluetooth that serves to arm and disarm the alarm with the control as well with the Android system phone through an application created with App Inventor and Arduino.

To do this project you only need a basic knowledge of App Invento and Arduino, as well as another little bit of car electronic.

I made this project as simple as possible so everyone can understand it, but if someone is interested, I also have a more complete version, with outputs for the horn and lights, as well as vibration sensor and open door detector and relay for cut the motor current, and also extra buttons in the application, to open the trunk and raise and lower the windows

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Step 1: Step 1: Parts

I bought all the parts on ebay at a good price from China, but if you do not want to wait 3 weeks for them, you can buy them from sellers in your own country, or locally

Bluetooth Module

There are modules of this type that are fed with 3.3v, but the one that we need must be from 3.3 to 6v

Remote Control 315MHz/433MHz

We can use any model of remote that we want and in any frequency, either 315Mhz or 433Mhz, but the remote must match the frequency of the receiver

315/433 Mhz RF
Transmitter And Receiver Modules

This, regularly sold in pairs, with transmitter and receiver, but we only need the receiver, the only condition is that it works at the same frequency of the remote control that we choose

Arduino Nano

This Arduino was chosen for being the molest with a good number of pins

4 Channel Relay Board

This is responsible for converting the 5v signals of the Arduino into 12v outputs to control the car directly

Buck Converter
Step-Down Adjustable Converter Power Module Regulator LM2596

This small will serve to convert the 12v power from the car to 5v to power the Arduino Nano and the Bluetooth module

Easy Install 10x 6
Pin HID Wire Connector Plug Male Female Harness Clips

It is not necessary to use this connector, but I liked it because in this way I can easily connect and disconnect the entire system

Plastic Project Enclosure Case

You can use the box that most convinces you, I prefer these to be able to hold them somewhere

Jumper Cable Kits

Indispensable to make connections easily

Step 2: Step 2: App Inventor

The required App Inventor knowledge is basic, only some buttons are occupied, the BluetoothClient and a few blocks


Download app:

Step 3: Step 3: Arduino

I have simplified this project to the maximum so that it is easy to understand and only basic knowledge of Arduino is needed.

Library: : “RCSwitch.h”, I downloaded this library from the internet, and it is in charge of RF remote controls

You need to download this library, unzip it and copy it into the Arduino library folder that is usually inside the "my documents" folder

Download Library:






int Arm=13;

int Desarm=12;

int Ignition=11;

int Star=10;

RCSwitch mySwitch = RCSwitch();

void setup()









void loop()


if (mySwitch.available())


long int value = mySwitch.getReceivedValue();

if (value == 0)


Serial.println("code error");




Serial.print("Received code");


////////////////FIRST CONTROL////////////


if(value == 8481906)//BUTON TO DESARM



Serial.println("led ON");



Serial.println("led OFF");




if(value == 8481905)//BUTON TO ARM



Serial.println("led ON");



Serial.println("led OFF");


/////////////SECOND CONTROL////////////


if(value == 9150562)//BUTON TO DESARM



Serial.println("led ON");



Serial.println("led OFF");




if(value == 9150561)//BUTON TO ARM



Serial.println("led ON");



Serial.println("led OFF");






char dato =;

if(dato == 'A')//BUTON TO DESARM



delay (100);



if(dato == 'B')//BUTON TO ARM






if(dato == 'I')digitalWrite(Ignition,HIGH);//IGNITION

if(dato == 'S')digitalWrite(Star,HIGH);//STAR

delay (2000);


if(dato == 'E')digitalWrite(Ignition,LOW);//CUT IGNICION


Download Code:

Step 4: Step 4: Diagram

The way to connect the device is a bit complicated, but not so much, you just need a car current tester, wire strippers and insulating tape.

Red Wire (Positive)

The supply current can be taken directly from the battery or any cable under the steering wheel with constant current, this is the current that is always there, even with the key in the OFF potition

Black Wire (Ground)

You can also take this from the negative of the battery or any wire or part of fixed iron under the steering wheel

Yellow Wire

In your car you need to remove the lid under the steering wheel and look for the wires coming out of the key switch, look for the ignition current, this is the current that comes out when you turn ON the key Switch

Blue Wire

This is the starting current, it is a short pulse that comes out from the key switch when we turn and hold the key all the way

Green Wire

This wire is the one that sends the signal to unlock the car, you will find it on the left side or in the center of the car, right where the unlock button is

White Wire

This wire is the one that sends the signal to lock the car and is also right where the lock button is

Once you found the wires just connect them all, it is only peel and splice

Step 5: Step 5: How Does It Work

Remote control RF 315Mhz or 433Mhz

The remote control has two buttons, one to arm and another to disarm the alarm
When the alarm is armed with the remote control, this one locks the car

When the alarm is disarmed with the control, this one unlocks the car

Android phone with App

The Android App has more features than the controls and it can be installed on all the phones you want

The first time you use this application you have to pair your cell phone with the Bluetooth receiver.

To do this you have to open your cell phone with Android system and open the phone settings, have the Bluetooth turned on and connect to your Bluetooth receiver, in case of asking for a password try with 1234 or 0000

Once you pair the receiver with your cell phone you can continue with the following

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    3 Discussions


    10 months ago

    Thanks a lot man. You ddescribed things so simpl. But I think that this Security system can be operated by any other rf remote having same frequency as the reciver. Correct me if I'm wrong ..

    1 reply

    Reply 11 days ago

    I stumbled upon this as a friend asked me if it's possible to add a comfort function for closing the windows to his remote. so I had a few talks with fellow students and and some thoughts how to realize it. so that system would be similar to this.

    actually it's not that simple and this guide missing a few things:

    * the signal the remote is sending is directly written into the code, as every remote is sending different signals, this need to be changed - maybe set as a variable
    * if you buy a remote you probably won't get the "code" too (the numbers in the program above "if(value == 9150561)" to recognize when which button is pressed), so you would have to find that first
    * some remotes can send encrypted signals, a set of different signals, need to be sent through some kind of hashing, 2-way communication, and so on. so not every remote would work out of the box without additional work not explained here
    * there is no security built in, so it could be quite easy to break that system

    but this instructables shows roughly how it works and it would be good to at least mention the above things so people know about them.