LED brightness

Using Arduino LEDs and Multiplexing
1

Hello, I am using different LEDs (red, yellow and green) in a project. Being my first project I have used 220ohm resistors as recommended in most tutorials. However all LEDs have different brightness, with the yellow being the brightest and the green the dimmest. Increasing the resistors values(I added two 10K resistors to the yellow leds) resolves the issue but I wander if there is anything else I need to consider before soldering.

I have used my multimeter to test voltage and current and I get the following values:

Voltage across LEDs:
green LED 1.988 V with 220 ohms
yellow LED 2.033 V with 220 ohms

Current:
yellow led:

  • 10.85 mA with 220 ohms
  • 2.39mA with 10220 ohms
  • 1.34 mA with 20220 ohms
    green led:
  • 10.96mA with 220 ohms
  • 2.37mA with 10220 ohms
  • 1.33 mA with 20220 ohms
2

Not really, some leds are brighter than others. Especially with the 2V leds, green isn't that powerful.

3

I don't think your resistor values are what you think they are. Maybe 1K not 10K.

To get 1.34mA with 20220 ohms would need a supply voltage of nearly 30V.

Steve

4

Thanks for pointing that out. Yes they are 1 K resistors.