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7809 not outputting 9v

Discussion in 'General Electronics Discussion' started by amirabbas1234, Aug 24, 2017.

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  1. amirabbas1234

    amirabbas1234

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    Aug 24, 2017
    hello . im a newbie to electronics.
    in advance sorry for my dumb questin
    i have a voltage regulator (7809) and im trying to get a 9v out of it. now i know that it is not gonna be 9v exactly and some thing near to it. but as u see in attached pics i get 12v.
    i cant understand whats wrong. is it my circuit???(see the attached images)
    or is the regulator broken????

    (for power supply im using an ac to dc adabtor witch gives me 14.1v)

    i would really appreciate some help
     

    Attached Files:

  2. Alec_t

    Alec_t

    2,882
    770
    Jul 7, 2015
    Welcome to EP!
    It's always advisable to read the datasheet for components you use. Here's how the IC should be wired.
     
  3. kellys_eye

    kellys_eye

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    Jun 25, 2010
    It also helps if we can see where the wires go and not just 'bits of them'.
     
  4. amirabbas1234

    amirabbas1234

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    Aug 24, 2017
    Thank u
     
  5. amirabbas1234

    amirabbas1234

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    0
    Aug 24, 2017
     

    Attached Files:

  6. Alec_t

    Alec_t

    2,882
    770
    Jul 7, 2015
    You don't seem to have a ground (-V) connection to the IC?
     
  7. amirabbas1234

    amirabbas1234

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    Aug 24, 2017
    the blue wire next to the brown wire on the bottom rail is the ground.
     
  8. Bluejets

    Bluejets

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    Oct 5, 2014
    Alec said it all in his first post..... Difficult to see but it seems you have it connected a-up. ie you have neg in term 1.
     
  9. amirabbas1234

    amirabbas1234

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    Aug 24, 2017
    sorry but could'nt understand ur last line
     
  10. Bluejets

    Bluejets

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    Oct 5, 2014
    Best if you show a complete picture of what you have connected. A drawing would suffice much better than photos of bits and pieces people have to mentally " glue" together. Very confusing as to what goes where.
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,411
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    Jan 21, 2010
    I think @Bluejets assumes that if the negative lead is blue, that the other blue lead is also negative.

    It's wise to use a red wire for positive and a black one for negative.

    You are missing the input and output capacitors too.

    Is this the first way you've wired it up? 12V is high enough to have damaged the device if you've connected it in certain wrong ways.

    What is your source of 12V?
     
  12. Rixen

    Rixen

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    Feb 16, 2016
    Hard to tell exactly what goes where on your fotos..

    I made a small schematic for you, try this, if it's still bad, your regulator is probably toast.. :)

    [​IMG]
     
    duke37 likes this.
  13. bushtech

    bushtech

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    Sep 13, 2016
    To me it looks like your resistor is sitting between pin 2 and the led and not between pin 3 and the led
     
  14. amirabbas1234

    amirabbas1234

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    Aug 24, 2017
    i did make ur schematics with my regulator and now it out puts 14v.
    u r right. the regulator is broken. bu i wonder , why?
    i havent done any thing to it.
    havent put more than 17 volts on the input pin.
    im sure i havent misplaced regulators vcc and gnd.
    the only thing i can think of is connecting regulators input pin to my vcc without any resistor in between.
    i know that for example connecting a led to vcc without tesistor damages it. but can connecting the regulator to vcc without resistor cause any damage to ic??

    Thanks in advance. u guys are the best
     
  15. duke37

    duke37

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    Jan 9, 2011
    The most likely fault is that you connected it backwards. A diode is often recommended across the regulator to protect it against reverse current.

    They don't like it up 'em.
     
    bushtech likes this.
  16. Audioguru

    Audioguru

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    Sep 24, 2016
    A resistor in series with the input of a voltage regulator will cause a voltage drop across the resistor which makes the input voltage to the regulator lower which might be too low for it to work properly. Usually a resistor is not used but it might be calculated properly to share heating.

    An LED is a load that draws as much current as it can so it needs a resistor in series to limit the current.
    A voltage regulator is not a load so it does not draw as much current as it can.
     
  17. Bluejets

    Bluejets

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    Oct 5, 2014
    Where did the 17v come from? You're not poking ac in there somewhere I hope.
     
  18. davenn

    davenn Moderator

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    Sep 5, 2009
    Because you initially connected it up incorrectly

    Steve already warned you of that in post #11
     
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