Help Building PSU

Thread Starter

MrYu

Joined Sep 26, 2011
42
i want to build with my own do you have a circuit which it can output 12 and 5v or what kind of transformer i will use, connection and components tnx
 

Thread Starter

MrYu

Joined Sep 26, 2011
42
For the Uc it must be 5v and for relays is 12v,. i'm planning to build one for my project. i don't like to buy a ready made coz i will not understand how the circuit of a psu works.
 

Thread Starter

MrYu

Joined Sep 26, 2011
42
i made a simulation which is 220v for source and i set it to 60hz,. i only get 11.2v for 7812 regulator
 
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absf

Joined Dec 29, 2010
1,968
Normally it's difficult to simulate transformers in proteus. If you put a voltmeter before the 7812, what voltage do you get?

Allen
 

bertus

Joined Apr 5, 2008
22,270
Hello,

You have wired the diode bridge wrongly.
The top wire of the transformer should go between D1 and D3.

Bertus
 

Thread Starter

MrYu

Joined Sep 26, 2011
42
i made another circuit do you think this will work in real life when i build this.
just curious the voltage before the 7812 is too high
 
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absf

Joined Dec 29, 2010
1,968
or this one the second circuit,. the problem with this is the output voltage in 7812 is 13.88v then drop to 12.55v
i will use this to drive the relay 12v. isn't too risky if the first voltage to go in relay is 13v or 12.5?
http://imageshack.us/photo/my-images/69/96701648.jpg/
Assuming the voltage after the rectifier is 15V. If the output current of 7805 is 800mA, then 10V is dropped across R1 10Ω resistor dissipating 8W. It would be quite hot.

The rest seems OK, but why did you parallel 2 x 1N5402 for each branch? One on each branch should be adequate.

Allen
 

Thread Starter

MrYu

Joined Sep 26, 2011
42
how to configure this in trafo or the alternator. i get 50v before the voltage regulator 7812/7805?
 
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