Arduino Bluetooth Relay Switch

Rajkumar Sharma
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SKU: EL153725
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This Bluetooth Relay Switch enables users to control lights, fans, or other devices using a Bluetooth app on an Android device. The device can be controlled using a simple app. The project consists of an Arduino-compatible microcontroller (ATMEGA328), a 5V relay, a relay driver BJT, and an optocoupler, which provides isolation between the relay and microcontroller, ensuring noise immunity and preventing high voltage entering the DC circuit. The HC-05 Bluetooth module provides wireless connectivity between the Android app and the Bluetooth board. Screw terminals are provided to connect the load to the relay contacts, and a header connector is available to power the board with 5V. A power LED indicates the presence of power, and a relay LED indicates relay operations. The relay contacts can handle loads up to 7A/250V AC and 10A/24V DC. An 8-pin header connector is provided for Arduino programming and Bootloader load.

Bootloader and Arduino Programming

To test the board, download the Arduino code and upload it to the ATMEGA328 microcontroller. Before uploading the code, ensure that the Bootloader is loaded on the new ATMEGA328.

Refer to the connections diagram for Arduino programming and bootloader instructions.

https://docs.arduino.cc/built-in-examples/arduino-isp/ArduinoToBreadboard/

Bluetooth Android App Download

https://play.google.com/store/apps/details?id=com.giristudio.hc05.bluetooth.arduino.control&hl=en

Features

Power Supply 5V DC @ 100mA
Wireless Bluetooth Connectivity
On Board Power LED
On Board Relay LED
4 x 4 mm Mounting Holes
PCB Dimensions 74.61 x 28.89 mm

Connections

CN1: Pin 1 VCC 5V DC, Pin 2 = GND
CN2: Relay Contacts, Pin 1 = Relay Normally Closed (NC) , Pin 2 = GND, Pin 3 = Normally Open (NO)
D1: Relay LED
D3: Power LED
CN5: Bluetooth HC-05 Module

Schematic

Parts List

NO	QNTY.	REF	DESC.	MANUFACTURER	SUPPLIER	SUPPLIER PART NO
1	1	CN1	2 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5315-ND
2	1	CN2	3 PIN SCREW TERMINAL PITCH 5.08MM	PHOENIX	DIGIKEY	277-1248-ND
3	1	CN3	8 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5321-ND
4	1	CN4	DO NOT INSTALL
5	1	CN5	BLUETOOTH MODULE HC-05		ALIEXPRESS/AMAZON
6	2	C1,C3	10uF/16V CERAMIC SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
7	2	C2,C4	0.1uF/25V CERAMIC SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
8	2	C5,R8	DNP
9	2	C6,C7	22PF/50V CERAMIC SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
10	2	D1,D3	LED RED/GREEN SMD SIZE 0805	OSRAM	DIGIKEY	475-1278-1-ND
11	1	D2	1N4007 SMD	DIODE INC	DIGIKEY	S1MBDITR-ND
12	1	Q1	BC847AL SOT23-3	NEXPERIA	DIGIKEY	1727-2921-1-ND
13	1	RL1	5V RELAY	TE CONNECTIVITY	DIGIKEY	PB2032-ND
14	2	R1,R6	1K 5% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
15	1	R2	10K 5% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
16	2	R3,R5	4.7K 5% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
17	1	R4	470E 5% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
18	1	R7	1M 5% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
19	1	U1	ATMEGA328TQPF-32	MICROCHIP	DIGIKEY	ATMEGA328P-AU-ND
20	1	U2	PC817	SHARP	DIGIKEY	PC817X2NSZ9F-ND
21	1	X1	16Mhz	ECS IONC	DIGIKEY	X1103-ND