Look if it is okay and need recommendation

Discussion in 'General Electronics Chat' started by Lightfire, Jun 16, 2011.

  1. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    Hello folks,

    After about three days of sleeping, I'm live again!:D

    Okay, for my question for today. My question for today is all about fuses.:p

    Okay, please look at my attachments for a brief thinking.:D

    Okay, as you may see, there are two separated circuits. Each circuits has two fuses, one for positive and one for negative.

    Again, all the fuses has its own holder. One fuse, one holder for it.

    The two separated circuits' fuse ratings is 2 amperes. (Take a look at here for the image: http://www.rshelectronics.co.uk/product.php?id_product=220) (And for its holder: http://www.rshelectronics.co.uk/product.php?id_product=276)

    And the main circuit's fuse is 4 amperes. (Take a look at here for the image: http://www.rshelectronics.co.uk/product.php?id_product=222) (And for its holder: http://www.rshelectronics.co.uk/product.php?id_product=276)


    Lamp ratings: 12 volts, 5 watts
    Battery ratings: 12 volts, 12 amp-hours

    Now, here is the questions.

    1) For example, the first circuit has encountered short-circuit. Which fuse will first melt? (I am not talking about the main fuse.) I am guessing that the fuse for negative will be the one to melt first.
    2) Will these fuses will melt quickly after it exceeds the maximum ratings?
    3) Will these fuses will melt quickly after any encountering of short-circuit?
    4) For numbers 3 and 4 questions, which fuse/s will melt? Their own fuses or the main fuses?
    5) Is there any recommendation for the wiring of the circuits?
    6) If there is any short-circuit happened in any of the circuits and their fuse already melt, is it necessary to change its holder too?
    7) Any recommendations?

    Thank you very much for the any advise you gave. Any advises will be appreciated.

  2. debjit625

    Well-Known Member

    Apr 17, 2010

    Because electron flows from negative to positive, then no. Actually nobody can say which one will blow first ,but the physically weaker one will blow first that I can say.

    The time depends on the type of fuse, their are many types like fast blow fuse which blow very fast after it exceeds the maximum ratings and their are slow blow fuse which take longer time to blow after it exceeds the maximum ratings.

    It's the case of your question 2 i.e.. it gets short circuit then the fuse exceeds the maximum ratings.

    The main fuse is rated a bit higher i.e.. double so their maximum ratings are also higher so they will not blow at all,the 2 Amp rated fuse will blow every time.

    You have 6 bulb each rating 12volt and 5watt so the current rating for the bulb is 5/12 = 0.417 i.e.. 416.667 mA.

    So connect the bulbs in parallel and connect a single fuse of rating (0.417 Amp * 6 bulb = 2.5 Amp)2.5A or a bit more with the battery ,I connect fuse on the positive side. You don’t need that many fuse.

    No, but if the holder is damaged or melted then yes you should change it.

    Yes, you are the fuse king man..........

    Good Luck
  3. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    Thank you very much for your effort, debjit625.
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    Why do you have fuses on the positive and negative?? There is no need.. Just wasting money.