Password Protected Relay based PC Controlled Wireless Home Automation System with ATmega32 using 433MHz RF-I

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In this project, we will learn How to design a Password Protected Relay based PC Controlled Wireless Home Automation System with AVR ATmega32 microcontroller using 433MHz RF Part-I. Here, we use the PC keyboard as the input device to enter the password to control the appliances i.e 2 bulbs and 2 fans. Also, we will display the status of each appliance in the PC. The password is a 4 digit number. In our case the password is “1234” which can be changed in the program. To gain access of the system, the user has to enter the correct password.

PC will send the control signal(ASCII value of pressed key value) to the ATmega32 microcontroller through its serial port. But current generation PCs and Laptops do not have serial port in them, so we will use a USB to Serial converter cable which will create a virtual serial port in the PC /Laptop. Again, the output of USB to Serial cable can not be connected to microcontroller directly as the output voltage of USB to Serial Cable corresponds to RS-232 level. And the ATmega32 microcontroller needs TTL/CMOS voltage levels. For this, we will use MAX-232 voltage converter which will convert RS-232 voltage level to TTL one and vice-versa.

The ATmega32 microcontroller will read the serial output of MAX-232 through its USART. First the user will enter the 4 digit password, each digit of which will be displayed in PC as star(*) and microcontroller will compare the entered password with the set password. The system will ask to enter password till the correct password is entered by the user. After the correct password is entered, the microcontroller will receive the appliance control signal from PC and it will process the control signal to know which key of the PC keyboard is pressed. After knowing which key of the PC keyboard is pressed, the ATmega32 microcontroller will send the required 4 bit signal to the HT12E encoder of RF transmitter circuit. The HT12E will encode the 8 bit address and 4 bit data given to it and then it will transmit the encoded signal serially to the RF module. The RF module will transmit the encoded data and address wirelessly.

At the receiver end, the RF receiver module will receive the encoded 4 bit data and 8 bit address. Then, it will transmit the encoded signal serially to the HT12D decoder which will decode the received signal to 8 bit address and 4 bit data. After decoding, the HT12D will compare the received 8 bit address with its local 8 bit address. If the received address and the local address are same, then the received 4
bit data is sent to its output pins else the received data is discarded. The 4 bit output of HT12D is sent to the Quad Relay Driver to turn on and off appliances.

Here, we will use 2 keys of the Keyboard to control one appliance. One key will be used to turn on and the other key will be used to turn off the appliance. So, for four appliances, we will use 8 keys of the keyboard. Apart from these 8 keys, we will use 2 more keys to turn on and off all appliances at a time. Now, press different keys from the PC and control the appliances as you want.

Control Keys	Appliance Status Change
1	Appliance 1 On
2	Appliance 1 Off
3	Appliance 2 On
4	Appliance 2 Off
5	Appliance 3 On
6	Appliance 3 Off
7	Appliance 4 On
8	Appliance 4 Off
9	All Appliances On
0	All Appliances Off

Softwares Required

Hardwares Required

Name	Quantity
AVR Trainer Board-100 with ATmega32	1pc
AVR USB Programmer	1pc
12V, 1A DC SMPS Adaptor	2pc
Quad Relay Driver	1pc
RS-232 Driver Board	1pc
433MHz RF Transmitter & Receiver Board	1pc
Power Supply Board	1pc
Home Appliance Board	1pc
1 to 1 Connector-Female to Female	6pc
10 to 10 FRC Female to Female Connector	2pc
USB to Serial Cable-Y-105	1pc