All of my green LEDs are very dim. I usually use a 220 ohm resistor and it is always very dim. All of my other leds are bright. Is this normal and can I make it brighter?
Show us a good schematic of your circuit.
Show us a good image of your wiring.
Give links to components.
Posting images:
https://forum.arduino.cc/index.php?topic=519037.0
Note voltage drops.
Post your code, using code tags.
Dim LEDs sometimes result from a pin declared as INPUT instead of OUTPUT. Using digitalWrite(pin, HIGH) on such a pin turns on the pullup resistor, dimly lighting the LED.
Or, are you using a 3.3V Arduino?
On a breadboard..... try a 180 ohm resistor and see what happens.
What voltage are you powering them with?
pinMode( myPin, OUTPUT ) ?
Very roughly speaking there are two types of green LEDs. Old green LEDs with forward voltage ~2V which are quite poor - the brightness @20mA is comparable to red LEDs @2mA. New green LEDs have forward voltage ~3.5V and are much brighter - about the same as blue and white LEDs, more than the red LEDs.
Also yellow LEDs are often poor.
As Larryd and other have pointed out, green LEDs have a different voltage drop, they therefore need a resistor calculated for them, not the same value as for other colours if you are concerned about brightness. Measure the voltage across the LED and calculate a resistor value accordingly.
yeetus420:
All of my green LEDs are very dim. I usually use a 220 ohm resistor and it is always very dim. All of my other leds are bright. Is this normal and can I make it brighter?
Either you have a low voltage supply, or old (not high brightness) LEDs. Before the '90's most LEDs were
extremely low brightness (about 1000 times less than today's types). Someone's dumping their old stock
perhaps?
ok. i will try lower resistors and try and figure out the voltage drop. thanks guys! 
What voltage are you powering them with?
yeetus420:
All of my green LEDs are very dim. I usually use a 220 ohm resistor and it is always very dim.
The key words here are 'ALL your green LEDs are dim', and 'usually use a 220 ohm resistor'.
This would just mean that it is most likely necessary that a smaller resistance value is needed. So testing could be done using a breadboard. Apply the same DC voltage that you usually do, and test brightness for cases where the resistance value is smaller than 220 ohm, such as 180 ohm, or even 150 ohm.
And use your multimeter to measure the supply voltage. You could even measure the current through the resistor too - for each case.
If the brightness improves with smaller values of resistance, then that would be good.
And - alternatively - if you're using a breadboard for testing, and if you have a variable voltage supply (eg. an adjustable lab supply), then you could see what happens if you keep the 220 ohm resistor, and then just gradually and slowly raise the supply voltage. This lets you see if the LED is able to get to that brightness (that you want).
Green LEDs are a pita. They’re always too bright or too dim. Especially next to a RED one.
Hi,
Do you have a DMM?
Thanks.. Tom..
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