Saturday 12 December 2015
Thursday 10 December 2015
Inside a Cell Phone
On a "complexity per cubic inch" scale, cell phones are some of the most intricate devices people use on a daily basis. Modern cell phones can process millions of calculations per second in order to compress and decompress the voice stream. If you have readHow Cell Phones Work, you know that they can transmit and receive on hundreds of FM channels, switching channels in sync with base stations as the phone moves between cells.
If you ever take a cell phone apart you will find that it contains just a few individual parts:
- A microscopic microphone
- A speaker
- An LCD or plasma display
- A keyboard not unlike the one we saw in a TV remote control
- An antenna
- A battery
- An amazing circuit board containing the guts of the phone
The circuit board is the heart of the system. Here is one from a typical Ericsson cell phone:
In this picture several of the components are identified. Starting from the left you the see the Analog-to-Digital and Digital-to-Analog conversion chips. You can learn more about A-to-D and D-to-A conversion and its importance to digital audio in How CDs Work. The DSP is a "Digital Signal Processor" -- a highly customized processor designed to perform signal manipulation calculations at high speed. This DSP is rated at about 40 MIPS (Millions of Instructions per Second) and handles all the signal compression and decompression. The microprocessor (Ericsson phones use an ASIC version of the Z-80) and memory handle all of the housekeeping chores for the keyboard and display, deal with command and control signaling with the base station and also coordinate the rest of the functions on the board. The RF and power section handles power management and recharging and also deals with the hundreds of FM channels. Finally the RF (Radio Frequency) amplifiers handle signals in and out of the antenna.
What is amazing is that all of that functionality -- which only 30 years ago would have filled the entire floor of an office building -- now fits into a package that sits comfortably in the palm of your hand.
Wednesday 9 December 2015
DC Motor Speed and direction control over GSM Mobile/Modem
This is a DC Motor Control Device which controls the stepper motor through messages received as SMS or GPRS Packets and also sends acknowledgment of task. These devices are designed to remotely control the DC Motor from anywhere and anytime. This remote control DC motor control device is possible through embedded systems. The toolkit receives the SMS, validates the sending Mobile Identification Number (MIN) and performs the desired operation after necessary code conversion. The system is made efficient by SIMs so that the SMS can be received by number of devices boards in a locality using techniques of time division multiple access. With this in mind, we have designed the project to work with sim300 technology.
The speed of the motor is measured using contact-less speed measurement technique. Speed control is done using PWM (Pulse Width Modulation) method. User can send SMS messages to control the motor speed and direction. A GSM modem attached to the control unit handles automatic SMS sending and receiving process. As this monitoring and controlling can be done by any mobile phone, we provided a security feature by implementing password-based protection. User has to send the password along with the commands to be controlled.
The purpose of this project is to control the speed and direction of DC Motor using Microcontroller and GSM Modem with password protection. This uses a PWM (Pulse Width Modulation) technique to control the speed of motor from 0% to 100%.
The SMS can be sent to any mobile user of any service provider with no or minimum charge. This system is designed using a GSM modem. The GSM modem is configured as a receiver. The SMS sent by the user is written in a particular format. The controller receives the message and decodes it and identifies the task to be done and the SMS received by the controller is decoded, and the proper message is displayed on the LCD by the microcontroller.
GSM Modem connected to microcontroller unit is used to control the motor and know the motor live speed. Microcontroller automatically reads the SMS messages stored in the SIM card and takes necessary action like speed control, direction control etc. There will be a particular code that needs to be sent through SMS to set the speed and get the speed from the DC motor.
Components
- GSM Module – SIM 300
This GSM Modem can accept any GSM network operator SIM card and act just like a mobile phone with its own unique phone number. Advantage of using this modem will be that you can use its RS232 port to communicate and develop embedded applications. Applications like SMS Control, data transfer, remote control and logging can be developed easily.The modem can either be connected to PC serial port directly or to any microcontroller. It can be used to send and receive SMS or make/receive voice calls. It can also be used in GPRS mode to connect to internet and do many applications for data logging and control. In GPRS mode you can also connect to any remote FTP server and upload files for data logging.
This GSM modem is a highly flexible plug and play quad band GSM modem for direct and easy integration to RS232 applications. Supports features like Voice, SMS, Data/Fax, GPRS and integrated TCP/IP stack.
- PIC 16F887
The PIC16F887 is one of the latest products from Microchip. It features all the components which modern microcontrollers normally have. For its low price, wide range of application, high quality and easy availability, it is an ideal solution in applications such as: the control of different processes in industry, machine control devices, measurement of different values etc. Some of the features are as follows:-
· RISC Architecture
· Oscillator Support 0-20 MHz
· In Circuit Serial Programming Option (ICSP)
· Watch-Dog Timer
· Brown-out Reset (BOR) with software control option
· Power saving sleep mode
· Enhanced UART Module
· 256 bytes EEPROM
· PWM output steering control
- Motor Driver IC – L293D
The L293 and L293D are quadruple high-current half-H drivers. The L293 is designed to provide bidirectional drive currents of up to 1 A at voltages from 4.5 V to 36 V. The L293D is designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V. Both devices are designed to drive inductive loads such as relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage loads in positive-supply applications. All inputs are TTL compatible. Each output is a complete totem-pole drive circuit, with a Darlington transistor sink and a pseudo-Darlington source. Drivers are enabled in pairs, with drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN.
When an enable input is high, the associated drivers are enabled and their outputs are active and in phase with their inputs. When the enable input is low, those drivers are disabled and their outputs are off and in the high-impedance state. With the proper data inputs, each pair of drivers forms a full-H (or bridge) reversible drive suitable for solenoid or motor applications.
Block Diagram
Circuit Diagram
GSM technology capable solution has proved to be controlled remotely, provide industrial security has achieved the target to control different industrial appliances remotely using the SMS-based system satisfying user needs and requirements GSM technology capable solution has proved to be controlled remotely, provide industrial security and is cost effective as compared to the previously existing systems.
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