The purpose of the project is to build a

mobile charger that can be used to charge

the cell phones with 1.5 volt pencil cells.

The cascoding technique of transistors are

being used for this purpose.a

The work is divided mainly into 3 stages

1.study each and every component in detail

2.Assemble the components

3.finalizing the model with precise charging

1 x transistor bc557

1 x transistor sk 100

1 x 4 1.5 volt pencil cells.

4.7k Ω ,

Green led

4.7 volt zener diode.

Most of the Mobile phone batteries are rated at 3.6 V/500 mA. A single pen torch cell can provide 1.5 volts and 1.5 Amps current. So if four pen cells are connected serially, it will form a battery pack with 6 volt and 1.5 Amps current. When power is applied to the circuit through S1, transistor T1 conducts and Green LED lights.

When T1 conducts T2 also conducts since its base becomes negative. Charging current flows from the collector of T1. To reduce the charging voltage to 4.7 volts, Zener diode ZD is used. The output gives 20 mA current for slow charging. If more current is required for fast charging, reduce the value of R4 to 47 ohms so that 80 mA current will be available. Points A and B are used to connect the charger with the mobile phone.

Here is an ideal mobile charger using 1.5

volt pen cells to charge mobile phone while

travelling. It can replenish cell phone

battery three or four times in places where

AC power is not available.

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ELECTRO SCHEMSTICS.COM

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B.HARSHA VARDHAN REDDY

13BEE1026

The purpose of this project is to make a

soil moisture tester circuit in which we can

know the level of moisture in the soil by the

way to decide to water the plants or not.

1.study each and every component in detail

2.Assemble the components

3.Test the working of the circuit by testing

with different moisture soils

Resistors:R1 = 100kΩR2 = 2kΩ7R3 = 2kΩ2P1 = 500kΩ preset HCapacitors:C1 = 470μF 16V radialC2,C3 = 10μF 16V radialC4 = 100nFSemiconductors:D1 = 1N4001D2 = 1N4148D3,D4,D5 =LED, greenD6-D9 = LED, yellowD10,D11,D12 = LED, redIC1 = LM7805IC2 = LM3914-NMiscellaneous:Tr1 = mains transformer, secondary 6 V 200mA ( e.g., Monacor/Monarch VTR-1106)F1 =fuse, 200 mA, with PCB mount holderJP1 = short-circuiting jumperK1 = 2-way PCB terminal block, lead pitch 7.5mm

First we have started the building of circuit by LM3914IC.First we have connected all the LED’s to the IC in the order D3,D4,D5 =LED, greenD6-D9 = LED, yellow D10,D11,D12 = LED, red.

We have connected the two diodes D1(1N4001) and D2 (1N4148) to the IC

Then we have connected the resisters and capacitors accordingly as given in the circuit diagram.

Now we came to the jp1 ,the short circuiting jumper and connected accordingly.

Next we have come to another IC1LM7805 and connected in to D1 there by to the fuse and transformer which is connected to the mains and out is connected to the 10uf capacitors

Thus we completed the circuit of soil moisture tester

Thus by this circuit we can test the

moisture of the soil with touching the soil

and gives the accurate moisture level i.e

we can know the level to which we can

water the plants to protect plants from over

watering

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