Before 24/7/14. Please help me about electrical and electronic. Urgent.

Discussion in 'Homework Help' started by aqilahadenan, Jul 23, 2014.

  1. aqilahadenan

    Thread Starter New Member

    Jul 23, 2014
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    The question is : How to make a DC power supply with a fixed 12V output using a bridge rectifier.

    I hope you guys can help me as soon as possible.
     
  2. Aerb

    New Member

    Jul 9, 2014
    12
    4
    [​IMG]

    The only thing you are going to change in this circuit is, instead using 7809, you are going to use 7812. That's it.
     
    aqilahadenan likes this.
  3. bertus

    Administrator

    Apr 5, 2008
    15,646
    2,345
    Hello,

    This sounds like homework.
    Show us what you have done YOURSELF.
    That way we can see where you need some help.

    Bertus
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    At least Google it for yourself, instead of waiting for Aerb to Google it for you.
     
  5. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Hola Aerb,

    Nice quick response.

    What is the maximum current I could handle?

    Have you built the circuit? If so, could you explain this: "9V DC regulator using 7806"? That could confuse the OP.
     
    Last edited: Jul 23, 2014
  6. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    What maximum current do you need?
     
  7. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Aerb, seeing as this was homework, it would have been better if you had not simply given an answer. How do you expect the OP to learn simply by copying a schematic? Getting answers to homework is not the purpose of the homework forum.
     
  8. Aerb

    New Member

    Jul 9, 2014
    12
    4
    Hey atferrari,

    78xx family regulators are able to output current as much as 1.5 amperes. This is the max rating however, one must find the corresponding value of the spesific component using its datasheet.

    I used to make my own regulator circuits (5 volts and 12 volts) using the same schematics, so i found it convenient to share the one that i found on the internet. The thing is, that was the best i could find (in terms of simplicity), and i didn't think it would cause mess. I simply told to replace 7809 with 7812. Despite there is a such error on the image, i thought he would just follow my instruction. (Well, yes, the two components differ a lot)
     
  9. Aerb

    New Member

    Jul 9, 2014
    12
    4
    Sorry, you're right. But since he needed the answer fast, i wanted to give the answer straight forward. And this is a pretty simple circuit, you know, i think he'll learn while he's doing it.
     
  10. MrChips

    Moderator

    Oct 2, 2009
    12,429
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    When someone requests Homework Help from AAC urgently, fast, ASAP, before the assignment deadline, that is good enough reason for me to delay for at least a week.
     
    JoeJester and DerStrom8 like this.
  11. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    That's actually another point I wanted to make--students who say "URGENT" or "NEED BY xxxxxxxx" usually are saying that because they have not managed their time well. In my opinion, they should not be rewarded for this by simply being given the answer. They should still do the majority of the work themselves.
     
  12. aqilahadenan

    Thread Starter New Member

    Jul 23, 2014
    4
    0
    me: Yes , actually I have found the circuit similar to what aerb has given. i'm asking him because i want to confirm whether my diagram is correct or not before i proceed to the next step. I have done the research but need to confirm the diagram as soon as possible due to lack of time.
     
  13. aqilahadenan

    Thread Starter New Member

    Jul 23, 2014
    4
    0
    Yes , actually I have found the circuit similar to what aerb has given. i'm asking him because i want to confirm whether my diagram is correct or not before i proceed to the next step. I have done the research but need to confirm the diagram as soon as possible due to lack of time.
     
  14. MrAl

    Well-Known Member

    Jun 17, 2014
    2,423
    490
    Hi,

    Actually, the circuit given may not be complete anyway. The original was for 9v output and the transformer secondary was 16v, but now that we need 12v output that may not work as well anymore.

    The diodes can drop 2v and so we're down to 14v peak, and with only 470uf we may not be able to get a smooth constant 12v out, depending on the load current.

    These are aspects of the design that have to be thought about even though a reference design has been supplied. For example, maybe the cap could be increased, or else the secondary output voltage has to be increased by the difference 12-9. Just some things you have to think about.

    As others have mentioned, if you can tell us how you went about this in the first place we can then figure out what methods you are allowed to use and that includes what approximations your instructor is allowing. Without knowing this info we could end up giving you equations which you wont want to have to work with, or maybe you will, but we wont know.
     
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