Mobile The Future Home Maker

Posted by : Unknown Friday, July 26, 2013

I. EVOLUTION

Mobile, Mobile, Mobile. Its mobile everywhere! It’s hard to imagine life, which is as busy as a bee in this highly competitive world without a mobile. The history of wireless communications traces back to December 12, 1901, when renowned scientist and Nobel Prize winner Guglielmo Marconi could transmit across the Atlantic Ocean. A century later wireless communications were widespread and turned out to be the flourishing industry posing many challenges and providing many opportunities.

The advanced technology, improved wide-area cellular systems and wireless LANs promise to make mobile computing and communications field develop rapidly with full-blown services for mobile users and hence change the nature and scope of communication. Today, integrated services are provided with ease. Every field is a challenging field with lots of opportunities awaiting services from every talented person of the world. The mobile revolution has ruled almost every field making the future merely predictable and even possible. Now, everyone can pick a mobile and talk with a friend located in a different continent. Previously, voice calls were the only options. But the latest cell phones can send faxes, exchange text messages, e-mails, music and even connect to the Internet. Mobile computing is thus ubiquitous.

Mobile computing has benefited greatly from advances in many areas of technology. High-density VLSI fabrication techniques, heat dissipation and increased hard drive densities are some of the examples of progress seen on the desktop, which have also driven feasibility of mobile computing. Some of the important areas of future mobile device design are display devices, integrated circuits, hard drive and storage and input devices.

The applications of mobile computing are too many to mention and are even illustrious. A remote control is being used to operate our household appliances like television, microwave oven, etc. A single remote to handle all these appliances would be a convenient tool. To design such a “Multipurpose Mobile”, which controls the operation of television and other home appliances would be the future mobile. The design of such a home automation machine appears simple to operate but harder to design. In the present world, GSM phones have created a niche for themselves and are being used for various purposes that include serving a multipurpose mobile.

II. TINY - MOBILE AS A REMOTE CONTROL

The function of the circuit is to provide an input and output port capable of being remotely controlled using another mobile. Here, the control takes place in the form of SMS (Short Text Message Service). When the mobile receives a text message (example: “Activate Burglar Alarm”) the circuit recognizes it as a command and switches the output accordingly.

Apart from this, this device can also be used to notify the status of the input port. At any point if we wish to know the status of the input port, the device sends back a SMS describing the status of the input. SMSs are simple and convenient as they can be entered, stored and read directly on the cell phone itself. Incoming messages are completed with time of reception and stored automatically in the mobile’s memory. Also, SMS’s are fairly priced, as they don’t require precious real time bandwidth.

CIRCUIT CONFIGURATION

The only active parts are ATTINY12L and a transistor. Also, the capacitor C# is reversed to provide negative potentials required by the RS232 interface.

The TINY12L is an 8-pin microcontroller with 512 words of flash code memory, 32 registers, and a precious 64 bytes of EEPROM. Three AA cells, for a total of 4.5 volts, power the circuit.
As the TINY12L has an internal brownout, it can run safely without requiring a voltage regulator.
Apart from Vcc and GND, all of the eight pins are available - including RESET, and an internal oscillator running at a respectable speed of 1 MHz.
With 1 MIPS at our disposal, the serial communications can be handled entirely in software.
Precise timing is not sacrificed by means of an adaptive algorithm that adapts serial port speed to the internal clock variations as the battery discharges. The serial stream enters the chip through PB4.
Diode DZ4 and R4 cut the negative fraction and limit input swing. On the converse, the output stream from PB2 drives the transistor Q1.
On the collector, a negative voltage is derived from the input stream. In this way, the data output to the cell phone is a true bipolar signal. The output stream is used as well to drive a LED. It is connected straight to PB2, and flashes at every transmission.
The pin PB0 is connected to a jumper that tells the software to disable automatic notification of input changes. It is pulled up internally, the resistor R6 is used to resolve conflicts during in-system programming. It can be omitted if the ISP takes place with the jumper removed. All the pins are assigned to functions that don't impede ISP.
The input goes to pin PB3, which is pulled up internally; the output comes from pin PB1. Both have a small protection resistor connected in series.
The RESET pin is pulled up with an external resistor, because the internal pull up is a high value one.
By converse, lowering input impedance removes the risk of picking up noise emanating by the intense electromagnetic field of the mobile.

V. CODE ENCODING

The algorithm is very simple. During setup, the four messages used as commands and the two messages used as responses are stored in the phone memory, where they can be read back by the controller issuing the appropriate extended-AT command.
For every command message, the set-up routine extracts a unique 6-byte "signature" from the last message bytes, and stores it in EEPROM. The system expects that every message be stored in a fixed position, as shown in Fig. 4. To ensure this, delete all of the messages from the mobile prior to set up.

#7: FOR NEW INCOMING MESSAGES

#6: SET OUTPUT

#5: CLEAR OUTPUT

#4: PULSE OUTPUT

#3: REQUEST INPUT STATUS

#2: MESSAGE WHEN INPUT=1

#1: MESSAGE WHEN INPUT=0

Outgoing messages are in positions #1 and #2, for indicating a low input and a high input respectively.
Ingoing command messages are in position #3 (request to report the input status), #4 (command to pulse output), #5 (command to set output) and #6 (command to clear output). Position #7 is kept free for incoming command messages.
During operation, the device repeatedly checks the message memory #7 for the presence of a new SMS. When it finds a new message, it compares its signature against all the stored versions. If one of the signatures matches, the relevant command (pulse output, set output, clear output, or send-back input status) is executed.
Using signatures instead of the full text allows the system to save EEPROM, and makes arbitrary-length messages possible. The system is safe as well, requiring an exact match of the last 6 characters to accept a command.
The "send input status" command, as well as a level change of the input pin when the AUTOSEND jumper is open, causes a message to be sent out.
It is neither necessary to recreate the outgoing message by scratch, nor to store it in EEPROM, as it is sufficient to re-send the first or the second message from the mobile message storage, according to the status of the input pin.
At the end of the cycle, the message #7 is cleared from memory and the system is ready for a new command.
As an example, consider the control of AC in our homes. An SMS is sent by the master mobile which is interpreted by the circuit and passed on to the Slave mobile as a command which then controls the operation of AC. This message is first accepted as high input by RS232 interface connected to the mobile, which is then regulated by the Zener diode. This is passed through the transistor at the collector, which acts as a switch and sends it to the slave mobile.
The software implements low-power techniques, which extend battery life to more than a year of continued use using AA cells.
The TINY12 is perfectly suited to run on batteries. Most of the time the controller is in sleep mode, with only the watchdog on.
In this condition, power consumption is only 200 µA. Control is resumed when the watchdog expires (a couple of seconds), or when the input pin changes. When running the required current is about 1 mA, for a period as short as 20 msec.
Every 10 short breaks (about 20 sec) the micro controller starts a longer dialogue with the mobile, requiring an extra 840 mS at 1,2 mA.

VI. WORKING

The device is very simple to use. The text messages for both commands and readouts are fully customizable by the user. Plain text messages like “Active burglar alarm” or “Main engine is running” are OK. It has to ensure that at least one out of the last 6 characters is different for every command. To prepare the system for set up, first switch on the mobile and then connect it to the main system designed using a suitable data cable. This is the “slave phone”, to differentiate it from the “master” phone used to issue commands. To set up a new set of messages, just send them in the usual way; using the cell phones itself for editing, according to the sequence below.

First, begin from the slave mobile:

Delete all the messages currently in memory.
Send to master the message for the input low condition, e.g. "THE INPUT IS LOW"
Send to master the message for the input high condition, e.g. "THE INPUT IS HIGH".

The messages above must be sent anyway, even if the input port feature is not used.
Next, it is time to move to the master mobile that is the phone used to issue commands:

Send to slave the message for requesting the input status e.g. "WHAT IS THE INPUT STATUS?"
Send to slave the message for pulsing the output e.g. "PULSE OUTPUT".
Send to slave the message for clearing the output e.g. "SWITCH OUTPUT OFF".
Send to slave the message for setting the output e.g. "SWITCH OUTPUT ON".

Again, all of the messages must be sent even if a specified command is not used. When all the seven messages are received, press the CONFIGURATION button on the TINY. The LED flashes until setup is complete. When the system is running, the LED flashes once every 20-25 seconds.

VII. ADVANTAGES

TINY MOBILE is a simple, flexible and portable solution useful for a wide range of applications.
It is a very optimized design, that doesn't even use a voltage regulator, and makes profitable use of every feature of its components: EEPROM, brownout, internal oscillator, watchdog, wakeup on pin change, in-system programming, sleep modes.
The code is dense, including power management and adaptive baud generator in just 417 out of 512 words available. Still, there is enough space for adding new features or to modify the behaviour to suit your personal taste. For example, the same alarm can be used to notify three different phone numbers instead of one.
The user interface developed is remarkable. Most of the work is carried on the cell phone. In a way the user knows, that a pushbutton and a single-page user manual is all that it is needed.

5. Also, the range of communication can be limited by limiting the range of receiving of the mobile employed by simply modifying the circuit in it without any change in software.

VIII. APPLICATIONS

It can be used to make an extended range remote control operated from anywhere in the world.
It can monitor if a machine is running, or some threshold is surpassed in the industry. The technical staffs are alerted automatically and can remotely operate an immediate countermeasure.
Commercially, a home automation system can be conveniently controlled and monitored from the cell phone.
To enhance even further its wide applicability, the circuit is very small and battery operated.

FUTURE OF MOBILE COMPUTING

The Mobile computing is just as broad as traditional computing. Mobility opens up new venues for interesting and unique products and services are possible only in a mobile environment. As people tend to think and work in places other than at the desk in their office, mobile computing allows the use of the computer as a tool where it is needed, not where a wire does tie it. Examples include the familiar executive working on a laptop while in transit, the field engineer having remote electronic access to technical documentation and diagnostics as well as emerging applications such as automated inventory (or) baggage checking with RFID devices and location dependent services such as local maps (or) weather reports.

CONCLUSION

Mobile computing has a bright future ahead. After the evolution of JAVA, a platform independent language, mobile computing seems to have a wide range of applications. One need not be surprised when a day might come where the mobile phone will be the homemaker, controlling all the operations of a house right from switching off the light and fan, once we leave the room to locking our house. It will also find its applications in areas of defence and aerospace. In the next decade this area is going to be widened finding its application in a large number of fields thereby ushering into a new area of computing world. To design a DREAM MOBILE, a mobile that serves as an INTELLIGENT MULTI-PURPOSE MOBILE should be our aim, that though looks harder to design but not unattainable. The well-known GSM phones are employed for this purpose since they are compatible to work over long ranges around the globe.