Think how cool it would be if you are able to control your AC appliances just with a touch of your Android smartphone. All you need to tap on your phone and you can easily switch ON/OFF your lights, fans and other home appliances. AVR micro-controllers provide a great platform to build such interesting projects and I have used ATMEGA8 micro-controller which is based on AVR.
Why prefer Bluetooth??
It is preferable to use bluetooth because nowadays people have their smartphones with them all the time, since the smartphones have bluetooth facility in them, thus it's better to use bluetooth rather than using RF remotes or IR remotes.Have you ever seen people carrying remotes???
Using bluetooth has many of its own advantages :
2.Easy to use.
3.It works in short distance range(i.e. upto 10mtrs.)
4.Anyone can find free bluetooth apps on android and many more.
If you ask me, why I made this project?? My answer would be simple because I am way too lazy and want to control things sitting at one place. Don't want always to get up to the switch boards just to switch things ON and OFF.
Step 1: Parts & Components Required
1. ATmega8 micro-controller 1nos.
2. ULN2803 1nos.
3. SPDT 5v Relay 3nos.
4. V-reg 7805 & LM317 1nos. each
5. Terminal blocks 6nos.
6. Breadboard 1nos.
7. 5v Regulated Power Supply 1nos.
8. HC-05 Bluetooth module 1nos.
9. Resistors, capacitors, diodes, etc.
10. 16MHz crystal oscillator 1nos.
11. Some wires and jumper wires
12. Most importantly an Android phone with BluControl v1.0 or above installed on it.
Step 2: Bluetooth Module
For setting up a bluetooth module, an i'ble can be found here. For creating 3.3v output for the bluetooth module, I have used LM317 IC v-reg with a 10k potentiometer.
Step 3: ULN2803A : What N Why???
Applications of ULN2803a include relay drivers, lamp drivers, etc. And that's what we need, relay driver. The ULN2803A has a 2.7-kΩ series base resistor for each Darlington pair which makes it operable directly with TTL or 5-V CMOS devices.
Step 4: Building the Circuit
Bluetooth module works on 3.3v only for which another power supply section has to be made. For this I have used LM317 voltage regulator which can provide output ranging from 1.2v to 36v. The potentiometer is used to vary the output voltage.
Remember to use a potential divider circuit which steps down the 5v serial output(Tx) from the micro-controller to 3.3v for the bluetooth module.
Always make sure to connect Rx of your bluetooth module to Tx of the micro-controller and vice-versa.
Step 5: ALGORITHM
What the system does is it simply receives the instructions in ASCII format from the bluetooth enabled Android smartphone using the bluetooth module and pass it on to the micro-controller. The micro-controller does the main processing part and for that purpose we need the code, please make your own.
What happens when the controller receives a particular ASCII value it switches ON or OFF a relay. And the relay acts as a switch for AC appliances. I have used some flag variables which check whether a particular relay is ON or OFF. A particular ASCII value is assigned for one and only one relay.
When an ASCII value is passed for the first time, it switches ON the relay and if the same value is passed again, the relay gets switched OFF.
Step 6: Android Cellphone
We are using an Android application named “Bluetooth Terminal” which can be easily found on Google Play Store and installed on the phone.
Bluetooth Terminal is an Android application that is a VT-100 terminal emulator for communicating with serial devices using a Bluetooth module.
One can download this application from here https://play.google.com/store/apps/details?id=es.pymasde.blueterm&hl=en
All you need to do is just open up the bluetooth manager in your Android smartphone and connect to the Linvor bluetooth module. You may require a password to connect to the module, the default password is 1234.
When the pairing is done and the module gets connected, press the any key that you have set for switching the relays.