LED drive calculations
Tessellated Circuits: Home => Old Home => LED bias calcs.  

This calculator provides a few typical LED forward voltages, though actual devices, even of the same colour, can vary by quite a bit. It uses values from the Wikipedia LED page  for the nominal voltages, but these are not always representative. The last entry in the drop-down list is the most useful: you can enter the actual data sheet value of forward voltage at the current you wish to operate at.

Enter LED and circuit Information:

[A]

[V]

The supply voltage is too low for the chosen number of LEDs at the LED voltage being used (1.9 V >= 0 V). Either/both a higher voltage or fewer LEDs might be needed.