Bluetooth Air Horn

As a long time lurker I finally decided this project was worthy of a write up (also I’m killing for an instructables tshirt). I love this site and hope you enjoy this project.

IMPORTANT!
Just a quick heads up, there are optional steps in this build. Your horn will be fully functional by step6 however I have included further options to monitor battery levels, change your Bluetooth device name and more!

https://youtu.be/F7qr1qPBbVQ

Also if anything isnt clear please let me know! I’ll amend this write up with anything I may have missed.

Step 1: Tools & Materials

Will keep the links updated if any go offline.

Components Required:

• Arduino Pro Mini 3.3v 8mhz or 5v 16mhz (link)
• UART TTL Programmer (link)
• HC-05 Bluetooth Module (link)
• Header Pins [about ~25 should do] (link)
• Hookup Wire (enough to connect the pins on the breadboard)
• Air Horn 134A (link)
• 180 Degree Servo Motor (link)
• Solder-able breadboard [cut to size] (link)
• 4 x AA Battery Clip [Not Pictured] (link)
• 4 x AA Batteries (Not Pictured)

Optional Extras:

• 2 Wire Voltmeter (link)
• Momentary Switch (link)
• Super Capacitor (Not Pictured) (link)

Tools Required:

• Soldering Iron + Solder
• Hot Glue Gun
• Flush Cutters
• 3D printer (or 3d printing service online)

Step 2: Flashing the Arduino

First of all you’ll want to flash your Arduino. If it didn’t come with the header pins soldered you’ll need to solder the 6 pins labeled:

GND, GND, VCC, RXI, TXO, DTR (these will all be in a row on the bottom of your dev board)

Once you have soldered the pins you’ll need to connect them to your FTDI Programmer as follows:

FTDI —-> Arduino

DTR —-> DTR

RXD —-> TXO

TXD —-> RXI

+5v —-> VCC

GND —-> GND

Now upload our test code (you can find the code here also):

#include <Servo.h><br>#include <SoftwareSerial.h><br><br><p>Servo hornServo;  // create servo object to control a servo<br>SoftwareSerial BT(10, 11); 
char a; // stores incoming character from other device
int pos = 0;    // variable to store the servo position</p><p>void setup() {<br>  
  BT.begin(9600);
  BT.println("Air Horn Active");
  hornServo.attach(9);  // attaches the servo on pin 9 to the servo object
  hornServo.write(10);  // sets the servo position</p><p>}</p><p>void loop() {<br>
if (BT.available())
  {
    a=(BT.read());</p><p>    if (a=='1')
    {
    hornServo.write(90);              // tell servo to go to position in variable 'pos'
    delay(15);
    BT.println("");
    delay(350);
    hornServo.write(10);              // tell servo to go to position in variable 'pos'
    delay(15);
    }
    
    if (a=='2')
    {
    hornServo.write(90);              // tell servo to go to position in variable 'pos'
    delay(15);
    BT.println("");
    delay(400);
    hornServo.write(10);              // tell servo to go to position in variable 'pos'
    delay(15);
    }
    
    if (a=='3')
    {
    hornServo.write(90);              // tell servo to go to position in variable 'pos'
    delay(15);
    BT.println("");
    delay(500);
    hornServo.write(10);              // tell servo to go to position in variable 'pos'
    delay(15);
    }</p><p>    if (a=='4')
    {
    hornServo.write(90);              // tell servo to go to position in variable 'pos'
    delay(15);
    BT.println("");
    delay(600);
    hornServo.write(10);              // tell servo to go to position in variable 'pos'
    delay(15);
    }
    
    if (a=='?')
    {
      BT.println("Send '1' for a sharp blast");
      BT.println("Send '2' for a longer blast");
      BT.println("Send '3' for a decent blast");
      BT.println("Send '4' for a deafening blast");
    }   
  }
}</p>

Step 3: Assembling the Board (Placement and Power Soldering)

This step will require a few connections and some patience however it is quite straight forward.

NOTE: you can also perform this step on a regular breadboard without soldering however it will render your final product a little less portable.

Placement:

Components for this step:

• Arduino
• BT Module
• 3 Male Header Pins
• Wire

We must place the flashed Arduino and the Bluetooth module (HC-05) on the breadboard in any orientation we see fit. Ensure that the breadboard you are using does not group and bridge rows of pins. On the PCB-Way breadboard I used, each pin was independent.

Solder the following pins together:

Wire Out –> Arduino –> BT Module –> Header Pin

Red Wire –> VCC –> VCC –> Middle Pin

Black Wire –> GND –> GND –> Bottom Pin

Note: there are 2 GND pins on the Arduino, you can use either.

The final image depicts where I have soldered a single black and red wire to the right of the Arduino for the power connection.

Source: Bluetooth Air Horn