I have 10 yellow-colored LEDs and ten 220 ohm resistors. I don't have any power source except the Arduino's 5 volt itself.

Is it possible to power all the 10 LEDs using the 5 volt equally? Or will the volts slowly diminish as the LEDs are powered along a series circuit? Also, is it possible to use only one resistor in the series or do I need to use a parallel circuit with one resistor after every LED?

Please help, I'm completely new to electronics and building a arduino project for my school expo.

  • \$\begingroup\$ A link to the data sheet might help but 5V is not a current. A typical yellow LED has a forward voltage of 2.0 to 2.4V so each LED takes 14mA max each with a 220ohm series resistor so 140mA total. You should be OK an Arduino is capable of supplying around 400mA \$\endgroup\$ Commented May 24, 2019 at 7:42

2 Answers 2



simulate this circuit – Schematic created using CircuitLab

Consider this 100mA layout for 2S5P array. You can always recompute R1 if this is blinding too bright ! Some are > 10 cd such as message signs.

enter image description here

You better read a datasheet so you know how not to handle them and how not to solder them. (ESD and 5sec max solder time >5mm from base.

  • \$\begingroup\$ I'm sorry but I'm a complete noob in these matters. Can you please explain your answer since I can't understand the schematic. \$\endgroup\$ Commented May 24, 2019 at 7:40
  • 1
    \$\begingroup\$ The flat edge on 5mm LEDs is the cathode or negative side which is the flat line bottom of the symbol. I only showed 1 string. YOu replicate this string in parallel 5 times. What do you not understand? Put the link to LED specs or equiv in question \$\endgroup\$ Commented May 24, 2019 at 7:42
  • \$\begingroup\$ @SayanjyotiDas alternatively use your 220 Ohm resistors instead of the 40 Ohm. This will give you 3.6mA through each LED which should be bright enough for most LEDs. \$\endgroup\$
    – Steve G
    Commented May 24, 2019 at 7:45
  • \$\begingroup\$ What is the purpose of your project? \$\endgroup\$ Commented May 24, 2019 at 7:46
  • \$\begingroup\$ It's actually a nuclear reactor simulator. \$\endgroup\$ Commented May 24, 2019 at 7:46

Firstly the Voltage isn't all that you need to know. The Amperage that can be drawn at that voltage is also important to know. In your Aurduino documentation it will tell you what the maximum current that can be sourced is. As already said in the comments, it will be around 400mA.

Current or Amps is how much power you have available, not Volts.

We don't know what LEDs you are using, but they will specify how much current they use. It will be a number in mA (milliamps). A typical 5mm yellow LED uses around 20mA.

Then you have your resistors, which Ohms Law (V=IR) will tell you how much current they will soak up. Your typical 5mm yellow LED will have a forward voltage of around 2.1V, so we will just make it a even number and say they are drawing around 15mA (it's actually less than that).

So that makes it around 15mA per set. Times 10 that's 150mA. If your Arduino can supply 150mA or more then you're good.

  • \$\begingroup\$ How did you end up with 35 mA? Lools like you added 2A+15mA. Hpwever, the current you calculated (correctly) that the resistors are drawing is the same current each LED is drawing, because they are in series. So, each set does 15mA. \$\endgroup\$
    – Huisman
    Commented May 24, 2019 at 10:01
  • \$\begingroup\$ I'm curious who thoughtlessly voted this answer up... \$\endgroup\$
    – Huisman
    Commented May 24, 2019 at 10:01
  • \$\begingroup\$ Hey, up vote just means you found it useful. It doesn't have to be correct :p \$\endgroup\$
    – hekete
    Commented May 24, 2019 at 10:35
  • \$\begingroup\$ How can wrong info in this case be useful? Leaves me guessing. Anyway, +1 for the nice (corrected) answer. \$\endgroup\$
    – Huisman
    Commented May 24, 2019 at 10:39

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