Hai…..friends. This is my second project…Have you ever used a readymade power bank? Hope yes! It’s very useful to new generation, especially during long trips. Its very easy to make it. There is nothing special in a power bank. It just uses batteries and voltage regulator IC’s. Actually the real production cost of a power bank is too cheap.

Here I have made a 3Ah power bank (just for 200 rs).

HERE ARE THE COMPONENTS USED IN MY POWR BANK

1.Battery---- 4.5v,,1.5Ah-------(x2)

2.voltage regulator IC---—LM7805------(X2)

3.usb port

4.switch

5.diaode

6.capacitor---100nf----(x2)

HERE IS THE CIRCUIT DIAGRAM FOR THE POWER BANK

LM7805 IC

This is a very cheap IC available form most of the local electronics shop.this IC is used to regulate the voltage to 5v. that iz this IC accepts an input ranging 5-9 v DC and gives out perfect 5v DC. Therefor in this case we get perfect 5v dc constantly. Here the two IC’s are connected in parallel to a about 2 Ampere current output, so that our device could be charged fastly. I have placed this IC on a heat sink which is used to absorb unwanted heat formed on the IC.it’s  preferable.

 

Images and detailz of LM7805

HERE TWO BATTERIES ARE CONNECTED IN SERIES TO GIVE A 9V OUTPUT TO THE VOLTAGE REGULATORS.THIS IC NEEDS a voltage above 5v to give regulated 5v output. If 5v or less than 5v is given as input the output will be varied.(it would be less than 5v).

Here diode is placed to prevent the backward flow of charge from our device to the power bank.

The capacitors clears any variations or  ac signals from IC.

The power bank works when the switch is on. This power bank can be charged from a DC adaptor of voltage ranging from 9 to 12 v.(((1 to 2 ampere input is preferred.))) ##The power bank must be switched off while charging.##

Finally the IC is connected to a USB port.IT must be connected correctly according the polarity.

Here is the photos of usb port(polarity is marked on photo)

Photos of power bank

If u r using an i-phone please connect a 200Ω resistor between the free legs of usb port(between the middle legs of USB port).So that your phone feels that it iz connected to its real charger and therefor get charged in normal speed……

Now u can make your own power bank!!!!!!!!ALL THE BEST!!!!

Please comment ur doubts and suggestions.

Thank you for visiting my site.

Ω

This is a very simple, cheap preamplifier which can be used for condenser microphone.Or it a can also be used as a simple low power audio amplifier………this amplifier can be prepaired by 2n3904 transistor which is very very cheap and can be operated even with 3v dc………normally condenser mic(ELECTRET MIC) cannot be connected directly to a mixer or an high power amplifier , becoz it generates a different signal which must be converted to normal sound signal and if u connect it directly to a normal high power mixeror amplifier no sounds could be heared bcoz of this property.So u must convert the signal using a condenser preamp circuit…..but condenser mic(ELECTRET MIC) is a high quality mic which can even trace out small soundz and can also produce heavy impulses for that soundzzz………….

So these type mics r used widley…… 

THE FOLLOWING DIAGRAM SHOWS THE DESIGN OF CIRCUIT :

COMPONENTS

R1=10K

R2=100K

R3=10K


C1=0.1uF

C2=0.1uF


Q1=2n3904

###3 to 9 v dc must be supplied….if u use an adapter as power source there causes a humming due to rectified dc…..(it can be reduced by using a filter capacitor)BUT I prefer clear dc from a bettery….so that the output sound would be very clear ###

This circuit can be easily made using the above itemz..it can be even made on a bread board or on a simple PCB…..u can get all these components from a electronic shop……NOW THE OUTPUT OF THIS CIRCUIT CAN BE GIVEN TO A MIXER OR AN AUDIO AMPLIFIER…….AND U COULD HEAR THE SOUNDS ON MICROPHONE VERY CLEARLY……

This amplifier can also be used as a simple audio amplifier…… if the input of condenser mic is replaced with output of a audio cable……….

That issssszzzzz……………

This circuit now works as a simple audio amplifier…..!!!

TRANSISTOR 2N3904 CONFIGURATION (FOR BEGINERZZ)

This circuit will surely work if itz assembled as mentioned above……I have tested and proved the sameeee…..(if needed you can attach a 10k variable resistor as volume control on the audio output …)

The wiring between mic and circuit must be done with shield wire to reduce noise…….

A sample shield wire…….

if u still have any doubt please comment the doubt in this site, and I will surely reply……. 

ALL THE BEST 4 UR PREAMPLIFIER CIRCUIT……

THANKYOU FOR VISITING MY SITE!!!!!

Ω