# DC power supply from AC through bridge rectifier

Discussion in 'Electronics Homework Help' started by vick5821, May 22, 2012.

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Jan 22, 2012
2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
I make it something like [REMOVED ANSWER]

Or something like that. It's a fairly meaningless figure because any additional load or other fluctuations will change it

Last edited: May 22, 2012
3. ### gorgon

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Jun 6, 2011
Normally the mains voltage will fluctuate a bit over the day/load, I would guess as much as +/-10%. Distance from the nearest distribution transformer will also count.
To get a stable 6V output from the power you'll need a regulator after the rectifier/capacitor bank. Most linear regulators need a bit of overhead voltage to perform, meaning that the base AC voltage from the transformer need to be a bit higher than the required output voltage.

The circuit you post will give around 7V unloaded or with a small load. Loading it will reduce the output as Steve said.

TOK

4. ### poor mystic

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Apr 8, 2011

If you're not sure what that all means why not post a cct diagram, which should include the required currents and voltages, and specifications of the transformer you intend to use.
We could tell you what it needs and how to connect it all up.

Last edited: May 22, 2012
5. ### vick5821

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Jan 22, 2012
I used a 6V transformer. And I want to step it from 240V to 6V. Unloaded means how ? the 10k consider as load ? how can I achieve near to 6V for the load ?

Thank you

6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
The best way is to use a regulator. Resistors won't do it.

7. ### vick5821

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Jan 22, 2012
we are not allowed to used regulator Just resistor and capacitor. Old time smoothing and filtering

8. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
And why didn't you post this in the homework help section?

It's not like you're new around here...

9. ### vick5821

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Jan 22, 2012
Actually this can be the general electronic stuff too

10. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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But if you post your homework in the wrong section you indicate to me that you want answers without doing any work yourself.

It doesn't make me want to assist you.

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12. ### poor mystic

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Apr 8, 2011

Anyway, the point of the exercise is probably not for you to make a stable power supply but for you to exercise your mathematical wits to correctly design a filter to specifications laid down in class. That's what I'd teach, if anything.

13. ### vick5821

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Jan 22, 2012
mathematical wits means ?

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15. ### poor mystic

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Apr 8, 2011

I presumed that a mathematical description of filter design had already been part of your course, and I apologise for any offense - .it's just that once you have such an understanding things get easier.
I may have over-estimated your intelligent laziness.

16. ### vick5821

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Jan 22, 2012
I am trying now..I put 5 series diode after the rectification output and I get around 6.2 + V. Is this practical or appropiate ?

17. ### poor mystic

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Apr 8, 2011
Ah,
but post a circuit diagram, please!

18. ### vick5821

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Jan 22, 2012
Posted in the first post

19. ### davennModerator

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Sep 5, 2009

post the pic in this forum

Dave

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