[alligator]

I have a circuit that I'm trying to wire up that will have six LEDs powered by one 9 volt battery. I already know the current limiting resistor values if all the LEDs are the same. What happens if I mix two different color LEDs that have different voltage drops and different maximum current ratings?


R1=22 Ohms (LEDs are blue, 3.5 volt drop and 100 mA operating current).
(Thanks to Ledcalc.com.)

I want to replace one of the blue LEDs with a white LED, and the current rating is 140 mA with an unknown voltage drop (View at Digi-Key).

Will my circuit still work? What if it doesn't have a 3.5 volt drop? Can you mix LEDs in a circuit with only one power source?

[RAILhead]

Yes, it'll work. You may end up with non-uniform LED brightness.

[ibookuser2]

If the voltage drop across the white LED is something other than 3.5V, then the voltage drop across the current-limiting resistor will change, and therefore so will the current through the series pair of LEDs. If the LED has a higher voltage drop, then the current through the resistor will be reduced and the blue LED in series with the white one will become dimmer. If the LED has a lower voltage drop, the blue one in series will become brighter. No matter what, the current through the white LED will be the same as the current through the blue one it's in series with, so with that schematic, you won't be able to run the white one at full brightness without blowing out a blue one.

[RAILhead]

You won't "blow-out" any LEDs.

[ibookuser2]

If you are running significantly more than the maximum rated current through an LED, then you will most certainly damage it.