ARDUINO-BASED BLUETOOTH DOORBELL

ARDUINO-BASED BLUETOOTH DOORBELL

Bluetooth doorbell is an advanced doorbell that shows your image to the person standing on another side of the bell. This doorbell is made already! You can buy a wireless doorbell in any hardware store. However, this one you make yourself! Even better, as you get more confident with Arduino, you can modify it to make it uniquely yours. For instance, what if your Arduino triggers a music player instead of a buzzer to let you know that someone has pressed the button? There are very useful devices for home use. The left side of figure 1 shows the doorbell button, and the right side of figure 1 shows the buzzer unit that is tucked away on a shelf inside.

Figure 1(a) The doorbell awaits visitors! (b) The buzzer unit sits discreetly on a shelf.

Parts Required:

In this project, one Arduino waits for a button press, while the other one sets off a buzzer when it detects that the button has been pressed. 

• 2 Arduino Unos
• 2 XBee wireless modules (Adafruit P/N 128)
• 2 Adafruit XBee breakout boards (Adafruit P/N 126)
• 2 mini breadboards (these are really small breadboards the sign of a postage stamp, Adafruit P/N 65)
• Button (SparkFun P/N COM-10443)
• A 330-ohm resistor
• Buzzer (Jameco P/N 1956776)
• Jumpers
• 9v battery clip (Jameco P/N 105794)
• 9v connector with barrel plug (Adafruit P/N 80)
• 1/4-inch MDF for enclosure backing and sides
• 5mm acrylic for enclosure front
• 1-inch #4-40 bolts
• Hot glue gunThe

1)   The Button 

The first part of this project is button. The button you use in the button unit, shown in Figure 2, is kind of intriguing because it has six connectors: two sets of positive and negative terminals that close when the button is pressed so you could have two circuits, both of which trip when the button is activated. The last two leads the white lugs in the photo are for powering the LED. Be sure to attach a resistor on the power lead so you don’t fry your LED inadvertently. I use a 330-ohm resistor in this project.

Figure 2: The button you use in the project has six connectors.

Instructions for Wiring up the Doorbell

The project consists of two Arduinos equipped with XBee modules and breakout boards. One Arduino has a button, and the other has a buzzer to sound out to let you know someone is at your door.

Button Unit

Let’s begin with the button unit (Figure 3), which consists of the following components:

A. 9V battery
B. XBee module
C. Mini breadboard
D. Arduino Uno
E. Button
F. Perfboard

Figure 3: The button unit before the acrylic is added.

Now, assemble these parts together as shown in Figure 4, and you can follow along with these steps:

Figure 4: The button unit consists primarily of a button, an Arduino, and the wireless module.

1. Plug in the XBee and its breakout board to a mini breadboard. 

2. Plug the XBee’s 5V to the 5V on the Arduino, its TX into RX, its RX into TX, and its GND pin to any free GND on the Arduino. 

3. Connect one of the button’s leads to pin 8 and the other to GND. (I use the breadboard to accommodate the GND leads coming from the button.) 

4. Solder a 330-ohm resistor and a jumper to the button’s LED’s power terminal, and connect the other end to the 3V3 port of the Arduino. The other terminal of the LED goes to GND. 

1) Buzzer Unit 

Next, connect the components that make up the buzzer unit, seen in Figure 5. These consist of the following: 
A. Arduino Uno
B. Mini breadboard
C. XBee wireless module
D. Buzzer

Figure 5: The buzzer unit waiting to be closed up. The outer holes are for wall mounting.

Next, use Figure 6 as a guide for connecting the various parts:

1. Plug in the XBee and its breakout board into a mini breadboard.

Figure 6: The buzzer unit consists of an Arduino, XBee, and buzzer.

2. Plug in the XBee’s 5V to the 5V on the Arduino, its TX into RX, its RX into TX, and its GND pin to any free GND on the Arduino. 

3. Connect the buzzer’s leads to the breadboard as well, as shown in Figure 6. You can connect them directly to the Arduino if you want, if you go this route, connect the red wire to pin 8 and the black wire to any free GND. 

4. To power the buzzer unit, use an Arduino-compatible wall wart or a 9V battery pack. 

Building the Doorbell Enclosures:

You next need to build the two enclosures for this project. The outside enclosure (see Figure 7) is designed to resist the elements.

Figure 7: The outside enclosure is made out of bent acrylic on a wooden back.

Button Unit Enclosure 

The button unit is the module that is on the outside of the door press the button to make the buzzer buzz! To make an enclosure, all you need is a box with a hole for the button, but I’ll show you how you can make one of your own. The one I made consists of a sheet of acrylic that I bent by heating it up, and then laying the flexible acrylic over a metal pipe to form a half-circle. I added the acrylic to a wooden back refer to Figure 4) to finish the enclosure. Here are the steps: 

1. Laser-cut the top, bottom, and back out of quarter-inch medium-density fiberboard  (MDF). If you don’t have access to a laser cutter, you can create a box out of pieces of wood, repurpose another container as an enclosure, or buy a commercial project enclosure. 

2. Laser-cut the front from 5mm acrylic. 

3. Glue the top and bottom wood pieces to the back wood piece. You might want to paint the wood! 

4. Attach the completed electronics. Use the #4-40 bolts for the Arduinos and hot glue for the buzzer, battery pack, and mini breadboards. 

If you aren’t using a laser cutter, you’ll need to drill mounting holes in the acrylic. You might want to mock it up using a sheet of paper first. 

5. Bend the acrylic front plate as described in the next section, “Bending Acrylic.” 

6. Attach the acrylic plate to the front so that the button can be pressed through the hole in the plastic. 

7. Install the unit outside your door of choice, and eagerly await your first visitor! 

Bending Acrylic 

For the outside button unit enclosure, you heat-bend acrylic (see Figure 8) to form a casing. This task is easy to learn because you don’t really need anything unusual or uncommon.

Figure 8: Bending acrylic is easy and gives a nice effect!

Acrylic (also known as Plexiglas) is also easy to heat and re-form. After it gets to the right temperature—not too hot or cool—the acrylic starts to bow and flex. When it gets a little hotter, it softens. That’s when you bend it how you want it, and let it cool into an awesome new shape! 

You need three things to get started: 

The acrylic to be bent 

I suggest 1/8 inch, though you might have luck with the thicker stuff. 

A form 

This is the surface over which the hot acrylic will cool and harden. You want this close to the actual curve you want the plastic to hold. The easiest form of all is the edge of a table. I used a rounded form a pipe to form the acrylic face. If you go this route, you’ll need to find a form that matches the curve of the shape you’re looking for. 

A source of heat

Heat guns (see Figure 9) and propane torches are common tools, though you can purchase commercial acrylic-heating strips (TAP Plastics has one for $80, P/N 169). Finally, you could heat up the plastic in an oven. This last technique is not for the faint of heart and you should definitely monitor the plastic closely so it doesn’t bubble or scorch.

Figure 9: Using a heat gun to soften acrylic.

Although you could conceivably use any heat-resistant surface to form your acrylic or even build your own out of pieces of wood in some respects, using the edge of the table is an easy choice because it bends the plastic perfectly, using gravity and the table’s surface to make a fairly perfect 90-degree bend. To bend plastic using the “edge of the table” technique, follow these steps: 

1. As shown in Figure 10, position the acrylic so the edge of the table is right where you want the plastic to bend. You’ll definitely want to weigh it down so it doesn’t move.

Figure 10: As the acrylic heats up, it starts to bend.

When it gets hot enough, gravity starts pulling the soft acrylic down, as shown in Figure 10. 

2. Position the acrylic how you want it to look and work quickly because after it cools, it becomes just as brittle as it was before. Don’t try to re-bend it without applying more heat!

Buzzer Unit Enclosure 

The buzzer unit doesn’t use plastic, because who wants plastic in their home? Instead, you can use a simple arrangement of wooden panels separated by bolts. I laser-cut two pieces of wood, one bigger than the other. (I ended up hand-drilling four additional holes, as shown in Figure 11, after changing my mind on how to proceed.)

PIN IT

Figure 11: I used laser-cut wood for the buzzer unit’s enclosure.

To connect the two pieces I used brass bolts, #10-24 and 2.5″ long, with brass washers and nuts. This enclosure is considerably easier to do than the other enclosure and it looks great!Wireless Doorbell Code

Upload the following code to your Arduino.

Button Unit Code

The Button Unit sketch consists of a loop that waits for the button to be pressed, then transmits a wireless alert.

#include <Wire.h>
const int buttonPin = 8;
int buttonState = 0;
void setup()
{
Serial.begin(9600);
pinMode(buttonPin, INPUT_PULLUP);
}
void loop() {
if (Serial.available() >= 2)
{
char start = Serial.read();
if (start != ‘*’)
{
return;
}
char cmd = Serial.read();
}
buttonState = digitalRead(buttonPin);
if (buttonState == HIGH) {
Serial.write(‘*’);
Serial.write(1);
}
else {
Serial.write(‘*’);
Serial.write(0);
}
delay(50); //limit how fast we update
}

Buzzer Unit Code

The Buzzer Unit code is similarly plain. The loop monitors serial traffic, then sounds the buzzer when it detects the command from the Button Unit.

#include <Wire.h>
const int buzzerPin = 13;
void setup()
{
Serial.begin(9600);
pinMode(buzzerPin, OUTPUT);
}
void process_incoming_command(char cmd)
{
int speed = 0;
switch (cmd)
{
case 1:
digitalWrite(buzzerPin, LOW);
break;
case 0:
digitalWrite(buzzerPin, HIGH);
break;
}
}
void loop() {
if (Serial.available() >= 2)
{
char start = Serial.read();
if (start != ‘*’)
{
return;
}
char cmd = Serial.read();
process_incoming_command(cmd);
}
delay(50); //limit how fast we update
}

Download Project Code Click Here

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