Home Automation with GSM

Embedded Systems: A Contemporary Design ToolEmbedded Systems: A Contemporary Design ToolEmbedded Systems: A Contemporary Design ToolDesigning Embedded HardwareEmbedded Systems: Architecture, Programming and Design, 2nd EditionEmbedded Systems: Architecture, Programming and Design, 2nd EditionEmbedded Systems: Architecture, Programming and Design, 2nd EditionEmbedded Systems: Architecture, Programming and Design, 2nd EditionEmbedded Systems: Architecture, Programming and Design, 2nd EditionEmbedded Systems Architecture: A Comprehensive Guide for Engineers and Programmers (Embedded Technology)

The system is implemented with ATMEL microcontroller based hardware unit. In current industry there exists lot of variants of 8 bit microcontrollers of MCS-51 family. We have chosen AT89S52microcontroller as the features include

-          8 Bit CPU for implementing the controller block

-          It has got 8 Kbytes of flash memory,  used  for storing the instructions 

-          It has got on chip UART module for communicating with GSM module using RS232 protocol.

-          It has got In system programming(ISP) feature

A 16X2 Liquid crystal character display(LCD) will be used for displaying the  data from the desired memory locations. The LCD is connected to PORT2 of the microcontroller.

A L293D voltage driver is interfaced to the microcontroller to drive the motor.

GSM is a digital mobile telephone system that is widely used because of its low power consumption and low cost feature. It is serially connected to the microcontroller via a line driver MAX232. GSM modem communicates using RS-232 protocol with the microcontroller. The RS-232 protocol is asynchronous serial communication protocol and works at the baud rate of 9600.

CODE

#include<reg51.h> #include "lcd.h" void transmit(unsigned char *); sbit light = P3^6; sbit fan = P2^6; unsigned char str[85]; unsigned char i,j,s; unsigned char c; void main(void) { TMOD = 0x20; SCON = 0x50; TH1 = 0xfd; TR1=1; light=0; fan=0; init_lcd(); delay_ms(1000); init_lcd(); display_lcd("UC BASED HOME"); cmd_lcd(0xc0); display_lcd("CONTROL (SMS)"); delay_ms(5000); init_lcd(); display_lcd("MODEM TEST? "); delay_ms(500); cmd_lcd(0xc0); delay_ms(1000); transmit("at"); SBUF=0x0d; while(!TI); TI=0; i=0; j=0; while(i<2) { while(!RI); RI=0; str[j]=SBUF; if(SBUF==0x0d) i++; j++; } str[j]='\0'; cmd_lcd(0xC0); display_lcd("MODEM OK"); delay_ms(2000); transmit("AT+CMGD=1,1"); SBUF=0x0d; while(!TI); TI=0; i=0; j=0; while(i<2) { while(!RI); RI=0; str[j]=SBUF; if(SBUF==0x0d) i++; j++; } str[j]='\0'; display_lcd("messgae deleted"); delay_ms(2000); /******** RECEIVING MESSAGES*********/ cmd_lcd(0x01); while(1) { transmit("AT+CMGL="); SBUF='"'; while(!TI); TI=0; transmit("REC UNREAD"); SBUF='"'; while(!TI); TI=0; SBUF=0x0d; while(!TI); TI=0; i=0; /* Gives the total characters received */ j=0; /* Gives total characters displayed on LCD */ s=0; /* Tells the START and END of decryption */ while(i<4) { while(!RI); RI=0; str[j]=SBUF; if(SBUF==0x0d) i++; j++; } cmd_lcd(0x01); str[j]='\0'; /*write_lcd(str[71]); write_lcd(str[72]); write_lcd(str[73]); write_lcd(str[73]); write_lcd(str[74]); write_lcd(str[75]); write_lcd(str[76]); write_lcd(str[77]);*/ write_lcd(str[78]); write_lcd(str[79]); write_lcd(str[80]); write_lcd(str[81]); write_lcd(str[82]); write_lcd(str[83]); delay_ms(2000); /*c=str[83]; cmd_lcd(0xc0); switch(c) { case '2': display_lcd("LIGHT ON"); light=1; delay_ms(1000); break; case '1': display_lcd("LIGHT OFF"); light=0; delay_ms(1000); break; case '4': display_lcd("FAN ON"); fan=1; delay_ms(1000); break; case '3': display_lcd("FAN OFF"); fan=0; delay_ms(1000); break; case 'A': display_lcd("LIGHT&FAN ON"); light=1; fan=1; delay_ms(1000); break; case '0': display_lcd("LIGHT&FAN OFF"); light=0; fan=0; delay_ms(1000); break; }*/ //str[83]=0; } } /********** TRANSMIT COMMAND TO MODEM **********/ void transmit(unsigned char *t_data) { while(*t_data!='\0') { SBUF = *t_data; while(!TI); TI=0; t_data++; } }

color sensor

Color sensor is an interesting project for hobbyists. The circuit can sense eight colors, i.e. blue, green and red (primary colours); magenta, yellow and cyan (secondary colors); and black and white. The circuit is based on the fundamentals of optics and digital electronics. The object whose color is required to be detected should be placed in front of the system. The light rays reflected from the object will fall on the three convex lenses which are fixed in front of the three LDRs. The convex lenses are used to converge light rays. This helps to increase the sensitivity of LDRs. Blue, green and red glass plates (filters) are fixed in front of LDR1, LDR2 and LDR3 respectively. When reflected light rays from the object fall on the gadget, the colored filter glass plates determine which of the LDRs would get triggered. The circuit makes use of only ‘AND’ gates and ‘NOT’ gates.
When a primary coloured light ray falls on the system, the glass plate corresponding to that primary colour will allow that specific light to pass through. But the other two glass plates will not allow any light to pass through. Thus only one LDR will get triggered and the gate output corresponding to that LDR will become logic 1 to indicate which color it is. Similarly, when a secondary colored light ray falls on the system, the two primary glass plates corres- ponding to the mixed color will allow that light to pass through while the remaining one will not allow any light ray to pass through it. As a result two of the LDRs get triggered and the gate output corresponding to these will become logic 1 and indicate which colour it is.
When all the LDRs get triggered or remain untriggered, you will observe white and black light indications respectively. Following points may be carefully noted :
1. Potmeters VR1, VR2 and VR3 may be used to adjust the sensitivity of the LDRs.
2. Common ends of the LDRs should be connected to positive supply.
3. Use good quality light filters.
The LDR is mounded in a tube, behind a lens, and aimed at the object. The coloured glass filter should be fixed in front of the LDR as shown in the figure. Make three of that kind and fix them in a suitable case. Adjustments are critical and the gadget performance would depend upon its proper fabrication and use of correct filters as well as light conditions

12V 30Amp Power supply

Using a single 7812 IC voltage regulator and multiple outboard pass transistors, this power supply can deliver output load currents of up to 30 amps.

Here the transformer is likely to be the most expensive part of the entire project. As an alternative, a couple of 12 Volt car batteries could be used.It is necessary that  the input voltage to the regulator must be at least several volts higher than the output voltage (12V) so that the regulator can maintain its output. If a transformer is used, then the rectifier diodes must be capable of passing a very high peak forward current, typically 100amps or more. The 7812 IC will only pass 1 amp or less of the output current, the remainder being supplied by the outboard pass transistors. As the circuit is designed to handle loads of up to 30 amps, then six TIP2955 are wired in parallel to meet this demand. The dissipation in each power transistor is one sixth of the total load, but adequate heat sinking is still required. Maximum load current will generate maximum dissipation, so a very large heat sink is required. In considering a heat sink, it may be a good idea to look for either a fan or water cooled heat sink. In the event that the power transistors should fail, then the regulator would have to supply full load current and would fail with catastrophic results. A 1 amp fuse in the regulators output prevents a safeguard. The 400mohm load is for test purposes only and should not be included in the final circuit