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POWER SUPPLY

agha

Mar 22, 2011
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Mar 22, 2011
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I WANT TO MAKE POWER SUPPLY OF 12 V 800 milli amps ....

I HAVE MADE POWER SUPPLY OF 12V BUT CURRENT IS TOO LOW ABOUT 300 milli amps


HELP NEEDED
 

davenn

Moderator
Sep 5, 2009
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there could be a number of reasons ....
lets see your schematic, is this power supply from mains voltage via a transformer
what are you trying to provide a 12V 800mA supply to ?

what is the rating of the mains transformer ? how did you measure the 300mA ?

cheers
Dave
 

agha

Mar 22, 2011
2
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Mar 22, 2011
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actually i providing 12v dc to my mini drill which is used for pcb driiling....

i used adapters but its not working on adapters when i made my own power supply it of 12v it was working fine but the drill was rotating very slow .... my mini drill requires 800 milli amps 12v :( :(

my transformer rating is 220 VAC input and is giving approx 14 VAC at output ..

component list
transformer
bridge rectifier 1A
capacitor 2200 µf 25v
capacitor 10 µf
LM7805 voltage regulator
100k potentiometre
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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The first thing is that a 7805 is not an adjustable voltage regulator, and even if it was, that circuit is not the way to do it.

Get a 7812, or something like an LM317 with the correct circuit.

The other possible issue is that transformer cannot supply sufficient current. You need to tell us the current (or VA) rating of the transformer. In your case a 1A or about 15VA would be the minimum I'd be happy with.

I'd also recommend a higher current bridge because the peak currents you'll be drawing each half cycle will probably be in excess of 1A.
 

hisfer

Mar 28, 2011
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Mar 28, 2011
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I WANT TO MAKE POWER SUPPLY OF 12 V 800 milli amps ....

I HAVE MADE POWER SUPPLY OF 12V BUT CURRENT IS TOO LOW ABOUT 300 milli amps


HELP NEEDED

I HAVE ATTACHED A CKT FOR U USE A TRANSFORMER WHICH HAS CURRENT RATING OF APPROX 2 AMPS so that u cant count for the losses also use largere capacitors to provide adequate current ie approx 100uf for output and 10 uf in parallel with the input
 

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