I have 5 LEDs Lilypad.
They are rated at Forward VOltage of 2V, so I guess this is the voltage required by the LED to light. IF = 20 mA and its rated at 78mW. Im using a drop off V of 1.8V and Im getting that from a 3V source it would require a 60Ω resistor. Im using this web calculator.
If I use 5V I would need 160Ω. Now the thing is I want to put about 5 of these in series. So they that means the resistance in the circuit would be greater due to the increased amount of LEDs in it and I should be able to get away with using no resistors at some point, up to a certain point, right?
R = (Vs - Vled) / Iled
this means that the Rtotal would be the (Vs - Vtotal leds) / I totalleds. But this would mean that Im doing the same to the num as the denominator so the result would be the same:
5v-(3*5V) = 5-15V = -10V all divided by I total leds = 20mA * 5 = 100mA. But that -10V seems wrong obviously. Please help me understand what Im doing wrong.
Im guessing I would need more voltage because if the forward voltage is 2V for each LED and I have 5, that means I need at least 10V?