Bluetooth SmartRoom




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,


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    6 years ago

    Very interesting project, I only have one issue with it, I am by trade a master carpenter also a computer tech, but my problem is not with function it is with how it is placed and appearance, would it not be better to have gotten a electrical inbox of some type to build it in and keeping it in the wall, it would be flush to it and it would have a clean appearance..
    I am sorry to say but not look like a box hanging on the wall (I don't mean this as disrespectful, but descriptive) ... I do not mean to sound rude, it is a great idea and thought, it just should have went more through the planning phase it seems to be very rushed and unrefined and/or finished...


    Reply 6 years ago

    In regard to the appearance, If I wanted to have it accommodated inside a metal enclosure and flush it with the wall which can also be done as on this instructable

    But due to the finished pre-made wiring in the house, this instructable is an attachment to the default available control to a Bluetooth control. If anyone by chance want to have a appearance as you have stated can follow the above link and have it. Cheers


    6 years ago

    kumaran who you know the connection for this part


    Reply 6 years ago

    Check out the updated schematic above.


    6 years ago

    Hey, I like your idea of using a standalone board instead of an arduino!!!


    6 years ago

    Nice project! A couple of comments. First, I think there might be a mistake in Step 6's schematic, the connection from the Load should go to the N.O. (normally open) side of each relay contact instead of the N.C. (normally closed) side. Otherwise the micro will need to keep the relay energized all the time to allow the existing wall switch to control the light. You could do it the way the schematic shows, but it seems counter-intuitive; normally you'd want the relay energized to turn on power to the load.

    Second, you shouldn't need 2W resistors for the 10K resistors connected on pins 12-15. At most there'd be 2.5 mW across them, so an 1/8W resistor is more than enough. You can use a 2W resistor, but they are more expensive than smaller ones (e.g. 1/4W or 1/8W).


    Reply 6 years ago

    Will edit the schematic as suggested. Actually I connected to NO. Minor diagramatic mistake above. Cool thing about 2W resistors, of course Atmega when idle loads 2.5mW 1/4W resistors will suffice. Thanks


    6 years ago

    Bluetooth is fun when no internet !


    6 years ago

    Nice !

    Bro how long does it works ! 1month ?1year??
    can we make a product ?