The microcontroller (PIC16f877A) is connected to the GSM/GPS module (SIM900B GSM/SIRF3 GSP) through the serial communication (UART) using the following specification : 9600bps as baud rate ;NO parity and 1 stop bit.
When the circuit is powered ,the microcontroller initializes the GMS/GPS module using the GSM/GPS COMMAND SETS.
The microcontroller is programmed to RECEIVED some set of UNIQUE commands from the GSM/GPS module as text message to perform specific action however the system also gives a responds (feedback) to the message received in a specified format .
Below are commands which must includes password only known to the user
- Begin+password
- Admin+password
- Noadmin+password
- Resume+password
- Stop+password
- ACC+password
- noACC+password
- check+password
- Calling/dialing
- SOS button
If the GSM/GPS signal are available the user can proceed with the initialization process but making sure that the password is kept in mind because that is the key or pin that the system decodes
The password assign to it now is 123456.
Begin+password command
When this command is sent as text msg to the gsm/gps module. the responds to the user number is begin ok as reply, thereby noting the number for other command but not as an administrators number.Admin+password
When this command is sent as text msg to the module. in a manner of admin+password+space+phone number (i.e admin123456 080xxxxxxxxx) the module reply to the user is admin ok thereby saving the number as and admin number that have the access to give command to the device and also receives response in a full duplex mode.noAdmin+password
When this command is sent as text msg to the module. in a manner of noadmin+password+space+phone number (i.e noadmin123456 080xxxxxxxxx) the module respond through the GSM/GPS as noadmin ok thereby discarding the number as that which have no access to give command to the device and receives response.However if this is sent including a number that is not recognized by the system the module response “authorized phone number is not in setup”
Resume+password
When this command is sent as text in a format of resume+password (i.e resume123456) knowing well that the number sending this is an admin number the module will respond resume engine succeed as text to the sender know as the admin and the microcontroller activate the relay (fuel pump ON).stop+password
When this command is sent as text in a format of stop+password (i.e stop123456) knowing well that the number sending this is an admin number the microcontroller will respond stop engine succeed as text to the sender know as the admin. (hence the microcontroller will receive a stop command from the module to operate a relay that automatically stop the vehicle from moving ( ie fuel line cut off)ACC+password
The ACC here represent ignition status of the car (ACC means accessory i.e a short form) when this is sent a text message to the module it activate the code from the program to monitor the ignition status of the car either ON or OFF this is achieved by sending ACC123456 as text.The respond gotten include either ACC is off/on! The lat/long details, speed, time are sent from the module to the user (admin)
noACC+password
when this command is sent as text in a format of noACC+password (i.e noACC 123456) it deactivate the monitoring function of the ignition status thereby if there is change in ignition position the microcontroller/module will not respond to it.check+password
when this command check123456 is sent as text to the system via a network the microcontroller respond by sending the status of GPS, GSM, door status, power level, ignition status (ACC) to the admin as reply.Calling/dialing
When a registered admin number want to know the position of the car or device ,he /she can simply place call on the device and the responds of the module is to hang up the call and respond in real time the longitude and latitude including the speed ,time and status of the door.SOS button
SOS simply means ( save our soul) its an emergency code which simply signify a call of distress(a police station number can also be attached as admin in case of emergency)when this button is pressed it will sent help me! With lat/long To all admin number register on the module for every 3 min to stop this, the admin have to send help me! To the microcontroller/module to stop its sending .
The microcontroller is program to wait for this command so as to perform the specified action ,any command sent that’s not among the UNIQUE command is ignored by the system.
The microcontroller is configured with 8Mhz crystal biased with 15pf capacitor
In an advent of wrong password the system will respond pwdfail but if no password is typed the system will not respond .
Mode of operation from the block diagram
THE 12 volts battery provide the source of excitation to the entire circuit, a voltage regulator unit is connected to regulate the voltage to 5v for efficient operation of the entire component of the design work. the microcontroller unit contains programs that communicates with the GSM/GPS module. the microcontroller can not communicate with the module without the aid of the level converter, hence the use of max232 converter. whatever command the microcontroller receives it must pass through the level converter unit before it gets to the PIC. the switching unit is responsible for stopping the vehicle when the command is given. the GPS generates the location of the device/vehicle at any time the device/vehicle changes location(long and lat) while the gsm is for communication between the admin and the device.
THANK YOU,I WISH YOU THE BEST OF LUCK (FROM SL TECH)
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