Is this circuit possible? And what resistor should I use?

  1. Hi all,
    I am a new member here.

    I am quite new to making circuits,etc. and have decided to make something easy-ish on a breadboard. I have included a diagram of what I am planning to make. I am using 6x white
    LEDs and a 9v battery. I was wondering what resistor I should use for
    this? Also, is this even possible? Do I have enough power to light up 6 LEDs not full power
    , as I know i dont have enough power for that, but even just a little bit bright? Would really appreciate
    any help on this. apologies for bad grammar, am in a rush!

    Thanks, Jamie
    Ireland
     

    Attached Files:

  2. jcsd
  3. davenn

    davenn 3,471
    Science Advisor
    Gold Member
    2014 Award

    Hey there Jamie
    welcome to PF

    1k resistors ( as currently shown) would be OK as a starting point, then increase or decrease a little to get the brightness you want

    Make sure you have the LED's the right way around :smile:


    Dave
     
  4. Baluncore

    Baluncore 2,516
    Science Advisor

    White LEDs drop a forward voltage of about 3.3V.

    Each LED will have (9V – 3.3V) / 1kR = 5.7 mA. I would have expected Ifwd to be closer to a typical 20 mA.
    For 20 mA you would use R = (9V – 3.3V) / 20 mA = 285 ohms, use standard value 270R.
    Total current will be 6 chains * 21.1 mA = 126.6 mA.

    You can save energy by wiring LEDs in series pairs. Then for 20 mA LED current you need a series;
    R = (9V – 3.3V – 3.3V) / 20mA = 120 ohms, a standard value.
    Total current will be I = 3 chains * 20 mA = 60 mA.
    So the battery should last twice as long.
     
  5. Thank you for a quick reply:) This helps alot!
    One more question though, can I use normal wire instead of using breadboard jumper cable wires?
    I have "normal" wire so if I could use it it would save having to buy the jumper cables.

    Thanks again,Jamie
     
  6. Baluncore

    Baluncore 2,516
    Science Advisor

    yes.
     
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