So is the Typical VF the "diode forward voltage"???
Or did you get the "Its Vfwd = 1.2V at 50mA,,,1.35V at 100mA" from somewhere else?
(I only listed the 1.2v AAA for arbitory purposes) What I need to know is which of the voltages is the "Diode Forward Voltage" so i can work out a suitable source and resistor.
According to the datasheet you posted, the continious forward current is 100mA.
The foward voltage drop of LEDs always varies consideriably, for the LEDs you're using it's 1.35V to 1.6V.
The wizard oversimplifies the issue a bit too much.
You need to know the maximum and minimum power supply voltage.
For example, if you have two LEDs and three batteries:
Suppose the battery voltage is 1.6V, straight off the charger and drop down to 0.9V when they need to be recharged. This gives a maximum supply voltage of 4.8V and a minimum voltage of 2.7V.
If we calculate the resistor values for 1.2V per cell giving a total of 3.6V, the current will be much higher at the 4.8V given by 1.6V per cell which might damage the LEDs.
If we assumed an LED voltage of 1.6V and both LEDs were only 1.35V more current would flow which could damage the LEDs.
The combined maximum LED voltage is 2*1.6 = 3.2V which means they'll get very dim as the battery voltage approaches this voltage so using four AA cells is a better idea.
As a general rule, use the minimum LED voltage and maximum supply when calculating the resistor value. In this case we need to use 1.35V per LED and 1.6V per cell.
When looking at the circuit when the power supply is at its lowest voltage, use the maximum LED voltage. In this case it's 1.6V per LED and 0.9V per cell.
This avoids burning out the LEDs or only using a quarter of the power in the batteries.
So is the Typical VF the "diode forward voltage"???
Or did you get the "Its Vfwd = 1.2V at 50mA,,,1.35V at 100mA" from somewhere else?
(I only listed the 1.2v AAA for arbitory purposes) What I need to know is which of the voltages is the "Diode Forward Voltage" so i can work out a suitable source and resistor.