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How to wire a LED

Discussion in 'LEDs and Optoelectronics' started by Mats, Jan 3, 2013.

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  1. Mats

    Mats

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    Jan 3, 2013
    Hi guys!

    I´ve got a product that I want to start manufacturing where I need to wire a 12v model rail way light to a 9 volt battery.

    Now I´m a complete noob when it comes to wiring but so far I´ve understood that I need to include some sort of resistance(?) in order to keep the battery from draining within minutes.

    I´ll much appreciate any help on this.


    Best Regards

    Mats
     

    Attached Files:

  2. BobK

    BobK

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    Jan 5, 2010
    If the light is a single LED with a resistor designed to work from 12V it will probably work as is from 9V but at a lower brightness. To bring it up to full brightness, you would lower the value of the series resistor that is already there. A 9V battery will be able to drive a single 20ma Led for about 24 hours.

    Bob
     
  3. cjdelphi

    cjdelphi

    1,096
    104
    Oct 26, 2011
    that's a little incan bulb, replacing it would be easy enough with an LED.... (try to finder an LED which is on the warmer side, or you'll not get the street lamp feel (high/low pressure sodium lamps) ...

    basically, what LED are you using?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    A really important benefit of using LEDs is that they have the same colour at all brightness levels.

    A small surface mount LED would probably work well in this case, maybe covered with a small blob of clear epoxy to simulate the glass.
     
  5. Mats

    Mats

    7
    0
    Jan 3, 2013
    Thank you.

    Thanks guys! these replies came a lot quicker than I had hoped.

    I don´t think the lamppost has a resistor built in, are you saying that the battery should last 24 hours without a resistor?

    If it is a normal bulb I prefer leaving it as is, but when I connect it to a battery it still only glows for about 10 mins.

    Thats a good idea, but I´m planning to produce quite a few of these objects, and I need to omit anything time consuming in the process of making them.

    Thanks to all of you.


    Mats
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    What sort of battery are you using?
     
  7. Mats

    Mats

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    Jan 3, 2013
    One of these
     

    Attached Files:

  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    With a battery that small it's not unexpected that it will have a short life driving a bulb. However 10 minutes does seem short.

    Can you measure the current it draws? (Or give us the exact specs of the bulb)
     
  9. Mats

    Mats

    7
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    Jan 3, 2013
    Hi.

    This is the information I´ve got on the bulb:

    • Brand: Everest.
    • Size: Approx. 75mm(H) or 2.95''(H) Inch.
    • Scale: 1:76~1:100,Suitable for OO scale or HO scale etc....
    • Color: Gray.
    • Operating Voltage: 12V, AC or DC Compatible.
      [*] Operating Current: 70mA.
    • Material:Coppery Column Model Lampposts.
    • Package Included: 10 complete lamps.

    Cheers


    Mats
     
  10. BobK

    BobK

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    Jan 5, 2010
    At 70ma you should be getting something like 6 hours out of a 9V battery.

    Bob
     
  11. Mats

    Mats

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    Jan 3, 2013
    Hi. I still only get like 10-15 mins and all the while the buld becomes dimmer and dimmer and then finally goes out completely. If I switch it off and wait half an hour and then turn it back on it lights up again and repeats the former.


    Mats
     
  12. BobK

    BobK

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    Jan 5, 2010
    Does it do this with a fresh new battery?

    Bob
     
  13. Mats

    Mats

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    Jan 3, 2013
    Yes.

    With cheap batteries and brand batteries alike


    Mats
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Are you running 1 of these lights or 10?

    Do you have a multimeter?

    I'd like to know what the current actually is when the bulb finally goes out, and the voltage across the bulbs.

    My suspicion is that the bulb (a 12V bulb) requires a relatively high voltage to appear lit, and the 9V battery quite rapidly falls below this.

    Have you done a comparative "tongue test" on a new and an old battery?
     
  15. Mats

    Mats

    7
    0
    Jan 3, 2013
    Hi

    I´m only running one with each 9volt battery.

    I don´t have a multimeter.

    I´ve done tongue test now, and there is definitively juice to begin with..


    Cheers.
     
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