Electronic – the correct supply voltage for LEDs

ledpower supplyresistors

I have a 5V supply power, three 5mm red LEDs, and each LED has 47-ohm resistor.

Two LEDs are bright but soon as I connect the third one all of them become dim.

Where am I going wrong? I'm new so a simple explanation will be appreciated.


simulate this circuit – Schematic created using CircuitLab

Edit: This might be a terrible schematic but I just started to learn about these things a few days ago.

Best Answer

Each red LED drops about 1.5V. So three of them takes 4.5V, leaving only 0.5V for the resistors.

0.5 / (47+47+47) = 0.0035A or 3.5mA. That's rather low.

If you were to remove two of the 47 ohm resistors, you would get

0.5 / 47 = 0.011A or 11mA. That's brighter, but still less than most LEDs can handle.