1. COIN BASED CELL PHONE CHARGER by sarin krishna k.r. 912711105017

2. ABSTRACT Now a days each & every person has mobile phone. During long travel we may forget to bring the charger. That time this coin based cell phone charger is useful. It contain 89c51 microcontroller, relay & regulators are used.

3. COMPONENTS USED: Power supply Transformer Diode Capacitor Regulators Micro controller Relay Mobile sockets

4. POWER SUPPLY SECTION 12-0-12V transformer is used. Primary of the transformer is connected to the main supply through ON/OFF switch & fuse. Secondary is connected to diodes to convert from 12V ac to 12V dc. Diodes are formed as two half wave rectifier. One is for delivering 12 to 15V supply to relay & capacitor 2200mfd/25V is used for filter purpose. Another side is fed the input of 7805 regulator and capacitor of 1000mfd/25 V is used for filter purpose to get pure dc voltage.

5. 89c51 Microcontroller It is a low power, high performance CMOS (Complementary Metal Oxide Semiconductor) 8 bit microcontroller. It is PEROM. The device is manufactured using high density nonvolatile memory technology. It is a powerful microcontroller, highly flexible & cost effective solution to many embedded control applications.

6. FEATURES 4K bytes of flash 128 bytes of RAM 32 I/O lines Two 16 bit timer/counters A full duplex serial port On-chip oscillator Clock circuitry

7. architecture

8. RELAY An electrical device which is activated by a current in one circuit to open or close another circuit. Relays are switching devices. it is the heart of industrial electronic systems. When a relay is energized contacts are made or broken. They are used to control ac or dc power. Relays are electro mechanical switches. The amount of electric power required to drive a relay is very small.

9. Block diagram

10. operation When we insert the coin, the coin detecting mechanism will detect the coin & send the corresponding signal to the Signal Conditioning Unit(SCU). Input signal is given to the microcontroller which activates the driver circuit for particular time period. Driver circuit consists of transistor which turn ON or OFF the relays. Relay is directly connected to the charging circuit. The charging circuit consists of different phone sockets thus we can charge our mobile phones.

11. advantages It can be useful while travelling and when we don’t have charger with us during travel. We just need a coin to charge the cell phone. Low capital cost. Easy to use.

12. disadvantages The life of the battery will be less than that of the given period. There is a chance of high voltage flow during charging.

13. CONCLUSION This project is very useful in today’s life. Because nowadays every person having cell phone. When they are going to long travel they may forget to carry the charger. This project is used to help that person by coin based charger. If it is placed in important places such as bus stand, petrol bunks, theatres then we will charge our mobile according to this project.