Introduction: Bluetooth SmartRoom

About: Electronics Hobbyist

This project will guide to have 4 Channel Relays for 4 different AC loads which can be controlled via Smartphone using Bluetooth.

This has the added features of:

1. Saving power state when electricity interrupts.

2. Can be controlled both from phone and local switches

3. Fully software controlled (Unlike two-wiring between relays and power switches).

Step 1: Required Components

1. HC-05 Bluetooth serial module

2. 4 Channel 5V 10A Relay Board

3. Microcontroller Type Dot Board

4. 28pin IC Base

5. 10K 2W Resistor 5pcs

6. Berg strip

7. 16Mhz Crystal

8. DC Barrel Jack

9. Led and holder

10. 5V Phone charger

11. Enclosure Plastic or Wooden

12. Securing screws (as required)

13. Miniature switches 4 pcs

14. 2Pin AC Socket

15. Arduino with DIP IC or USB UART Adapter (For porgramming the chip)

16. ATMEGA 8 with Arduino Bootloader

17. 22pf 2pcs

18. LM7805 and Heatsink with 0.1uF and 10uF Caps

19. Female to Female Dupont wires


Check out the images for the above mentioned components.

Total project components sourcing for me it took Rs.750 (Approx. 11$)

Google it with names to find availability with your local seller.

Step 2: Schematic, Testing and Uploading Microcontroller

Initially prepare the board for programming as per the following link

Once prepared use USB UART converter to upload the below sketch following steps from above link

MODIBT.ino =

Use Bergstrips for connection as shown in images.

Step 3: Soldering and Prototyping

Here I used a Dot Board compatible with Microcontrollers which was easier to solder.

Again its all own way of building a circuit in an stripboard.

Place 2W 10K resistors to pins12, 13, 14, 15.

1/4W is enough for pin 1.

Use Berg strip pins and Dupont wires whenever and wherever necessary.

Here I have attached my samples.

If you don't like this step you can spare an arduino instead.

Step 4: Enclosure Preparation

Place the components randomly and mark its location on board.

Visible components are Led, HC-05, 4 x miniature switches, 2Pin socket with 5V adapter.

Use Drill machine, Hand Files, etc to suit the components

Attached images for reference

Step 5: Adding Miniature Switches for Manual Switching

Here as shown have small switches, as mentioned before these are software controlled which keeps micro-controller pulled high and low to toggle the load status.

Here in Arduino coding I have used EEPROM to save the power status., so avoid unnecessary power cycles.

One terminal of all miniature switches are series connected to 5V directly as shown.

Step 6: Adding Relay Board to 230VAC

Here I have attached the schematic.

Analyse the default circuit.

Remove the old switches

Connect the disconnected wires to the Relay as shown in schematic

Place the assembled board, hang it safely


Step 7: Android App

I have used Bluetooth Serial Controller app to configure Bluetooth.

Here characters from A to H is used in serial communication between ATMEGA8 and HC-05.

Just open the app and set for any 8 buttons the characters A to H as shown in images.

The app has the option in hide unused buttons, and do it so.

Any queries,


Automation Contest 2016

Participated in the
Automation Contest 2016