First LED project, need some help double checking

Discussion in 'The Projects Forum' started by canedragon, Feb 11, 2013.

  1. canedragon

    Thread Starter New Member

    Feb 11, 2013
    Hey, so I am a total newbie with wiring in any form, and I decided to take upon this project of upgrading my LED hula hoop. It has turned into completely rewiring the thing. When it comes to putting the circuitry safely in the hoop I don't have a problem, but I do need some help double-checking what I'm going to do when my LEDs arrive.
    I used this: to help me out. My specs in that order are:
    • 3.7
    • 3.3
    • 20
    Then the amount of LEDs kind of varies. I have a total of 162 LEDs (32 from my old hoop that I took apart, 130 on the way.) I am hoping to use 100 if I can, all 162 if possible. In the original design that I took apart there were no resistors. It used a 3.6v 900mAh rechargeable battery and was just a simple parallel circuit made with paired speaker wire. Since like I said there were no resistors I am assuming that they are all 3.6v LEDs (forward voltage.)
    (I did find one type of LED that matched the types in the hoop already, and it listed 3.0-3.6v forward voltage. I made sure all the LEDs I ordered matched this.)

    So far I hope I am doing everything correctly!

    Anyway, here is my current schematic for when all my parts get delivered. I hope that it makes sense- I am a very visual person and text schematics are hard for me to understand.


    This example only uses 10 LEDs but, being repetitive again, I hope to use around 100. The battery is removable and rechargeable. (I got 3000 mAh because when using that calculator it says "the array draws current of 2000 mA from the source." and I am hoping to keep it going without a recharge for at least 45 minutes (if I read everything correctly it should go for at least an hour on this battery if not 1 1/2 hours)

    My question is, are my resistors placed properly? I've been searching a lot but a lot of the threads I come across use terminology I can't seem to compute. I need stuff like this explained to me like I'm 12, unfortunately.

    I'm using this tutorial mixed with a LOT of googling:

    Hopefully that will give some insight into how I'm wiring this. I don't quite have the parts yet (except for the original wiring) so I can't take pictures of resistors or anything.
    The connection I'm using will be much simpler, there will not be a switch, just a push button to uncollapse the hoop, slip the battery in, close the hoop and it will light up (which is what it did before I took it apart)

    I hope this all makes sense, I'm sorry for the wall of text. I just am afraid I'm going to end up shorting everything out or making something catch on fire, lol. I didn't need to explain that much I guess I just need someone to double check my wiring.
  2. canedragon

    Thread Starter New Member

    Feb 11, 2013
    This is on the third page with no response, so... bump?
    (It told me the message had to be longer than 5 characters)
  3. SonOfAnarchy ZA

    Active Member

    Jul 13, 2011
    Why dont you just use high bright LEDs the can handle 4v without a issue. the way you got it wired doesnt look right from my (limited) understanding you require just the first resistor not the rest
  4. canedragon

    Thread Starter New Member

    Feb 11, 2013
    I bought 3.6v so they would match the 32 LEDs I already have (which are specialty and I don't want them to go to waste)
    that is the part I couldn't really find info on, if I needed 1 resistor for the circuit or 1 for each LED. thanks.
  5. KJ6EAD

    Senior Member

    Apr 30, 2011
    You need a separate resistor for each LED but it only needs to be 20Ω since your supply voltage is so close to the Vf of your LEDs. The LED and resistor pairs should each be connected to the supply voltage, not chained as it appears in your drawing. I'd share a schematic but the AAC attachment manager doesn't work with Android.
    Last edited: Feb 15, 2013
  6. canedragon

    Thread Starter New Member

    Feb 11, 2013
    OK so I DO need a separate resistor. The way I have it wired in the drawing is the way it was already wired, as I understand it, it is a parallel circuit. Instead of being in a line however from the battery I have it looped, so that it can go inside the hoop tubing. this is also how the prodmod website says to connect them.

    The LEDs I ordered came with resistors, it says "1/4-watt 200 ohm resistors" does that mean 200Ω?
  7. tubeguy

    Well-Known Member

    Nov 3, 2012
    If you want to use 162 LEDS at 20ma each, then the total current draw would be 162*.020 =3.24 Amps. A 900 ma battery won't last very long.
    Options would be to reduce the current draw or use a much higher capacity battery.
    Yes those are 200 ohms.
    You need to use a small value resistor as suggested, the 200 ohm would allow very little current - very dim LED's
  8. canedragon

    Thread Starter New Member

    Feb 11, 2013
    Yeah, I have a 3000 mAh battery now to use. I will probably only end up using 100 LEDs.
    Thank you for the help on the resistors, I will find some smaller ones. The ones I got just came with the LEDs in one package so no loss really.
  9. canedragon

    Thread Starter New Member

    Feb 11, 2013
    Hello again. So I am working into my project and I just have a few more questions.
    I want to make sure these are the right resistors before I buy them (as mentioned before I need 20 ohm resistors)

    secondly, I am wiring my LEDs in parallel like this image (which is not mine):

    When I attach the resistors, can I just attach them to a leg of the LED like this?

    (I hope that makes sense)

    or does the resistor actually have to intercept the wires, like:


    where -- is say my positive wire, // is the wire coming off the resistor and (==) is the resistor body itself. Again, sorry, I don't know how to write real schematics or anything and am a very visual person so the pictures help at least me.

    one more Q- can I use hot glue over the wires once I am done to keep them in place. I know they are making a good connection but I am wary of using just electrical tape to insulate.

    thanks you guys again for all your help.
  10. bertus


    Apr 5, 2008

    The way you connected the resistor it will be shorted.
    You will have to connect the resistor in series with the led.
    I have tried to correct your drawing:


    I hope you can understand what went wrong.

    canedragon likes this.
  11. canedragon

    Thread Starter New Member

    Feb 11, 2013
    I understand this part now. Thank you!

    Does anyone know how to help with the other quick questions?