Step 1: COMPONENTS REQUIRED
- Bluetooth module (HC-05)
- AT89S52/C51/S51/C52 microcontroller
- Relay Driver ULN2003A
- Resistances and capacitors as circuit diagram depicts(below)
- power module(if the input is more than 5V or else not necessary)
- IC 7805(5V voltage regulator)
- 1000uF capacitor
- 10uF capacitor
- led and resistance(as per convenience so that led doesn’t get damaged)
IMPORTANT NOTE: USE 11.0592MHz crystal oscillator as this only gives a baud rate of 9600 same as bluetooth module. So to establish communication between microcontroller and HC-05 we need to match their baud rate just like “WALKIE-TALKIE frequency”)
Step 2: CIRCUIT DESIGN
The circuit diagram is as given above. This circuit can be improvised like :-
- the reset circuitry can be omitted if want to do reset through code.
- The 5V power supply circuit can be omitted if you have a 5V standard source.
- Relay of 6V can be used but the +ve pin should be connected through 6V supply.
- Relay driver IC acts as a NOT gate i.e. when signal from microcontroller comes to it, the output of ULN2003 is 0V, initially it’s active high. More bits of microcontroller port i.e. P2 port’s bit(e.g. P2.0,P2.1,P2.2-P2.7) can be connected to remaining ULN2003 IC input pins thus respective output can be obtained.
- Include P3 port with another UNL2003 IC.
- After circuit design the main thing on which the circuit will operate is the CODE that says on which signal which port will be 1 or 0!!!
Step 3: CIRCUIT EXPLANATION
The basic is very simple…
- You need a bluetooth enable host device i.e. mobile,computer or anything!! For the sending of command to the circuit.
- We have used a bluetooth module(HC-05 “HANDS & LEGS OF THE CIRCUIT” ) for catching the signal from paired host device and relaying the same to the microcontroller through its Tx pin to TxD of the later. But you can also use HC-06/07, Sable-x-R2, TIWI-uB1 etc.
- Now comes the microcontroller…”HEART & BARIN OF THE CIRCUIT”… receives data from bluetooth module and does the work according to the code written in it and REPLIES to the bluetooth module.(TxD to Rx)
- Pins of microcontroller gives output and thus connected pins of ULN2003 receives it and gives 0V(initially 5V) making the relay trip(work).
- Relay’s one leg connected to 5V(OR 6V) and another leg get 5V or 0V depending on ULN2003 output. When potential difference(voltage) across relay is 6V it works for 0-3V it doesn’t work.
BE CALM & INNOVATE & MAKE CIRCUITS…
The next edition of this circuit is wifi enabled, IOTs working on it.
THANKS TO INSTRUCTABLES
Step 4: CODE
I have written the code in embedded C format in Keil uVision… for the code email me…(firstname.lastname@example.org) I HAVE GIVEN THE PROTOTYPE OF THE CODE IN THE ABOVE PICTURE YOU CAN INNOVATE AND MAKE IT EITHER… WRITE PROGRAM>>SAVE IT IN “*FILENAME*.C” FORMAT>>BUILD>>GET HEX FILE>> AND UPLOAD…
I uploaded the HEX file to the AT89S52 microcontroller referencing to https://www.instructables.com/id/ARDUINO-AS-A-8051…
AGAIN THANKS TO INSTRUCTABLES… If any problem regarding this project contact me!!
CODE: C code for this project
Step 5: ANDROID APP
Read more: DIY Cheapest Bluetooth Controlled Home Automation