How do I connect a voltage regulator in this setup?

Discussion in 'The Projects Forum' started by Acegikmo, Jan 27, 2012.

  1. Acegikmo

    Thread Starter New Member

    Jan 27, 2012
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    Hello!

    I'm working on making a battery solution for a device which doesn't support it by default. I'm replacing the original outlet+adapter configuration with a single battery with a cable.

    I'm pretty sure I've got the right battery and the right voltage regulator.

    However, I'm not entirely sure how to solder this together!
    What I wonder is; Will this work? (See image)


    [​IMG]


    Which means, solder it together in the areas marked green, and the same with the little plug on the right.

    Thanks in advance :)
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    What is the type and voltage of your battery and what is the desired output voltage?
    Also the regulator type? If you´re using the typical 78xx series, remember that you need at least 2.5V higher voltage on the input. Also, what is the current requierd by the load?
     
  3. PaulEE

    Member

    Dec 23, 2011
    423
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    If your regulator is indeed a standard 78xx regulator and you do have the proper difference between the in/out terminals, and if you do not exceed the regulator's current draw, this setup looks fine.

    Remember to check polarity on that output jack!
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Keep in mind that the 78XX series of three terminal voltage regulators have a built-in thermal protection circuit. If you overload the device with too much current, the regulator will shut itself off until the overload is removed and the device cools down below it thermal temp limit. This typically saves the device from self destructing in an overload condition.

    hgmjr
     
  5. Acegikmo

    Thread Starter New Member

    Jan 27, 2012
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    The battery is a Lead-Acid battery at 12V.
    The voltage regulator is L7809CV 1.5 A.
    The adapter I'm trying to replace says 9V 1.7 A.
    The adapter has this symbol: http://upload.wikimedia.org/wikipedia/commons/8/84/Centre-positive.svg

    So I should connect the brown wire to the inner metal parts of the plug, and the blue wire to the outer metal part, right?
    According to the person at the store, the voltage regulator should be fine, even though the adapter says 1.7 rather than 1.5.

    I really have no idea myself, so if any of this is completely wrong, let me know!
     
  6. PaulEE

    Member

    Dec 23, 2011
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    Hook up the output of the regulator to the middle of the output jack.

    The adapter claims it can source 1.7 amps; whether or not your device ever sinks 1.7 amps is something that is up to you to decide...

    You also might entertain the idea of an inline fuse to avoid *POP* *FIZZ* (letting the smoke out of the regulator, wires, battery, or load device, or all those things!)

    Otherwise, you should be fine.

    What are you connecting this to?
     
  7. Acegikmo

    Thread Starter New Member

    Jan 27, 2012
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    I'm connecting it to a Kaossilator Pro, a synthesizer!

    What kind of inline fuse would I need in this case? Is it a 1.7 A fuse or something I need?
    I've never done anything with electronics before, so I'm not sure which parts to get and how to connect them
     
  8. PaulEE

    Member

    Dec 23, 2011
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    If you go to radioshack and ask for a "1.5 amp" slow blow fuse and inline fuse holder, they should be able to hook you up with those things.

    The fuse would simply go inline with the input of the regulator. It's just a safety measure for the equipment, that's all.
     
  9. Acegikmo

    Thread Starter New Member

    Jan 27, 2012
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    Shouldn't it be in line with the output of the regulator? Since that's the current/voltage that matters for the device, isn't it?

    I'm still a bit confused as to what fuse to get. I thought it should be a 1.7 A fuse, not 1.5. Or does it not matter that much? :)
     
  10. Pencil

    Active Member

    Dec 8, 2009
    271
    38
    Before the regulator will provide a measure of protection in case of
    short circuit at the regulator. The current is coming from the battery.
    The amount of current "before the regulator" and "after the regulator"
    is basically the same value.

    You probably will have trouble finding a 1.7A fuse. A 1.5A fuse will
    be more readily available, and probably sufficient, Yor adapter can
    provide a maximum of 1.7A, your requirements are most likely less.
    Check your device being powered, it may have a fuse for its own
    protection.

    You should also find a datasheet for the regulator you are using and look
    to see what capacitors are recommended from the input/output to
    ground, Usually a .22uF or .33uF is recommended on the input side
    and a .1uF on the output side. I believe this is a link to your DATASHEET,
    look at page 28, Figure 8. You may not need the capacitors recommended
    since you are powering from a battery but, it is always good practice to follow
    manufacturer recommendations.

    Another point to consider is if the current requirements of your powered
    device is more than a few milliamps, you will probably will need a heatsink
    on the regulator to avoid the possibility of overheating the regulator. If the
    regulator oveheats, it may shut down to protect it self, or be destroyed.
     
    Last edited: Jan 29, 2012
    PaulEE likes this.
  11. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Your circuit is missing the important input capacitor and output capacitor (mounted very close to the regulator pins) shown on its datasheet.
     
  12. Acegikmo

    Thread Starter New Member

    Jan 27, 2012
    5
    0
    Are those necessary?
    I hooked everything up, and it works perfectly fine!
    Haven't tried for more than a minute though, but still :)

    Thanks everyone for the help!

    Edit:

    The voltage regulator does get quite hot after a minute. Should I be worried?
     
    Last edited: Jan 29, 2012
  13. Pencil

    Active Member

    Dec 8, 2009
    271
    38
    Highly recommended. Without them the regulator could
    oscillate wildly and destroy itself. You wouldn't even know
    it was happening until it died.

    Add a heatsink, even if the regulator does not get hot enough
    to go into thermal shutdown, the lifespan/reliability will be greatly
    improved. In a pinch, anything that conducts heat attached
    securely to the tab of the regulator will help, although bona fide
    heatsinks are readily available.
     
  14. PaulEE

    Member

    Dec 23, 2011
    423
    32
    Do put caps on near input pins and do heatsink chip. Wise words!
     
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