FRIENDLY CHARGER FOR MOBILE PHONES

Most mobile chargers do not have current/voltage regulation or short-circuit protection. These chargers provide raw 6-12V DC for charging the battery pack. Most of the mobile phone battery packs have a rating of 3.6V, 650 mAh. For increasing the life of the battery, slow charging at low current is advisable. Six to ten hours of charging at 150-200mA current is a suitable option. This will prevent heating up of the battery and extend its life. The circuit described here provides around 180mA current at 5.6V and protects the mobile phone from unexpected voltage fluctuations that develop on the mains line. So the charger can be left ‘on’ over night to replenish the battery charge.

The circuit protects the mobile phone as well as the charger by immediately disconnecting the output when it senses a voltage surge or a short circuit in the battery pack or connector. It can be called a ‘middle man’ between the existing charger and the mobile phone. It has features like voltage and current regulation, over-current protection, and high- and low-voltage cut-off. An added speciality of the circuit is that it incorporates a short delay of ten seconds to switch on when mains resumes following a power failure. This protects the mobile phone from instant voltage spikes.

The circuit is designed for use in conjunction with a 12V, 500mA adaptor (battery eliminator). Op-amp IC CA3130 is used as a voltage comparator. It is a BiMOS operational amplifier with MOSFET input and CMOS output. Inbuilt gate-protected p-channel MOSFETs are used in the input to provide very high input impedance. The output voltage can swing to either positive or negative (here, ground) side. The inverting input (pin 3) of IC1 is connected to 12V stabilised DC voltage developed across zener ZD1. This makes the output of IC1 high. After a power resumption, capacitor C1 provides delay of a few seconds to charge to a potential higher than of inverting pin 2 of CA3130, thus the output of IC1 goes high only after the delay.

In the case of a heavy power line surge, zener diode ZD1 (12V, 1W) will breakdown and short pin 3 of IC1 to ground and the output of IC1 drops to ground level. The output of IC1 is fed to the base of npn Darlington transistor BD677 (T2) for charging the battery. Transistor T2 conducts only when the output of IC1 is high. During conduction the emitter voltage of T2 is around 10V, which passes through R6 to restrict the charging current to around 180 mA. Zener diode ZD2 regulates the charging voltage to around 5.6V.

When a short-circuit occurs at the battery terminal, resistor R8 senses the over-current, allowing transistor T1 to conduct and light up LED1. Glowing of LED2 indicates the charging mode, while LED1 indicates shortcircuit or over-current status. The value of resistor R8 is important to get the desired current level to operate the cut-off. With the given value of R8 (3.3 ohms), it is 350 mA. Charging current can also be changed by increasing or decreasing the value of R7 using the ‘I=V/R’ rule.

Construct the circuit on a common PCB and house in a small plastic case. Connect the circuit between the output lines of the charger and the input pins of the mobile phone with correct polarity.

Digital integrated circuit tester using microprocessor

The IC tester should be able to test some ICs to ascertain their functionality,state the actual fautly pin and give the necessary recommendations based on the fault detected as well as recommed the equivallent IC. The major instruments need are microproccessor, which will coordinate the activities of the components such as the socket were the IC will be inserted and the display gadget which will display the result.

Video Library-Management system

The current electronic world offers a lot of entertainment features to the people. In the electronic entertainment world the movie videos is one of the leading source. Lots of people are doing this entertainment feature through video libraries. There is a need for software for these video libraries which will assist them in a lot of ways. The project ‘Video Library-Management System’ consists of modules which are used to maintain the customers’ available, available movies, the video suppliers’ information, purchasing details, the member registration, issue of videos and their return status. The customer module covers the customer id, name, address, contact no, email address, city. This module allows the user to add, edit, and removal of customer details.

The movie module used to add, modify the movie details like movie title, movie cast, language of the movies, movie rating, hiring charges, no of copies available, description about the movies. The supplier module covers the supplier id, name, address, contact no, email address, city. This module allows the user to add, edit and removal of supplier details. The purchasing module consists of purchase no, supplier id, supplier name, supplier address, product item, quantity, unit, rate amount. The stock will be updated immediately after purchase.

The issue module maintain the information like issue no, movie id, movie name, hiring charges, customer id, customer name, issued days, scheduled return days. When the user return the videos the fine details if applicable also calculated and bill prepared accordingly. This software allows the user to generate detailed reports like the movies available, the customer details, the movies hired. These reports provide the detailed activity of the library. The language used is VB.NET to develop the GUI and MS Access as the backend to store the details.

MOBILE POSITIONING USING WIRELESS NETWORKS

The aim of the project is to find out the best possible accurate mobile location method and demonstrate it with the help of a cell planning tool. Also find the fundamental limitation associated with the mobile positioning based on available wireless network measurements. In this Project we will investigate the Wireless Systems for locating and tracking users or goods within closed or open environments .which are of great interest for the human society as well as for world economy. Typical applications are e.g. emergency services and avalanche victim search or in mobile computing applications, tracking of goods and any location aware services. pervasive computing ,location-sensitive content deliver direction finding ,asset tracking ,emergency notification ,locate avalanche victims.

Water purification plant control system

You are working as a design engineer at a company that specializes in water treatment plants. You have been given the task to develop the control system software for the 1st stage dosing system of a water purification plant for a manufacturing company. Dirty water, as result of the manufacturing processes, is pumped into a settling tank to allow impurities to settle. To promote the settling process a flocculant must be added to the water in the Mixing Tank before the water enters the Settling Tank.

The amount of flocculant required is directly proportional to the amount of impurities in the water. The amount of solids in the water can be measured using a LDR sensor, the amount of impurities reducing the amount of light passing through the water. There are 4 solenoid valves that control the amount of flocculant that is added to the dirty water in the Mixing Tank. The amount of valves to be opened depends on how clear the water is. If the water is clear, all valves would be closed and as the amount of impurities in the water increases so more valves will be opened. The control system must use a PIC16F88 microcontroller and the development work must be done using the Matrix Multimedia development board.

Micro controller Based Automobile Monitoring system

The aim of this project is to build a Micro controller Based Automobile Monitoring system. Using this system one can monitor the vehicle parameters to achieve safe drive. The system can monitor the km/h, engine temperature, fuel quantity, battery voltage, side stand status ect. Whenever any of these parameters goes beyond the set limits, the system will give alarm indication. All the parameters are displayed on liquid crystal display. This acts as an output media of the system. The brain of the system is the micro controller AT89S8252 that takes care of all the processing required. The controller is associated with components like ADC to ensure the analog values, temperature sensor to measure engine temperature, photo interrupter module to measure the speed, and keyboard to set the required limits.

Telephone record control

Circuit operation is as follows. When the phone is on hook the voltage across the phone line is about 48volts dc. When the phone is off hook the voltage will drop to below 10volts dc. When the line voltage is at 48volts the FET is off which causes Q2 and Q3 to be off. When the phone is picked up the FET turns on along with Q2 and Q3 which turns your recorder on. The tape recorder must be in the record mode at all times. As you can see the power source for the circuit is the phone line.