The last set of jumbo white LED's I used had an average forward drop of 1.7V, but varied by +/- 200mV over the 200 LED's used in the array. An important consideration is the current through the LED. Connect the LED to the meter leads, verifying correct polarity; Meter will indicate forward drop (usually 1V-3V for most LEDs.) 5 (System Voltage) = 2.4 (LED 1) + 2.4 (LED 2) + Resistor. The forward voltage drop across a white LED varies with the model, manufacturer, etc.

Resistor = 5 - 4.8. Now that you have the LED's forward voltage drop you can figure out how much voltage everything else in the "chain" will need to drop. What voltage drop basically means is that the voltage you send into the strip is not the one you receive at the end of the strip. The forward voltage of an LED, VF, is the voltage that must be applied across the leads of the LED, from anode to cathode, in order for the LED to turn on.. As you can see above, positive voltage must be applied across the LED from its anode to its cathode. Voltage drop is a decrease in voltage from initial power supply’s 100% voltage, across all part of an electric circuit. Superbright leds can go from 30mA up to several amps. An example, with cheap LED strip you can feed the strip on one end with 12v but once it’s gone through 5 meters of strip, it might have dropped down to 9v or even 8v because of all the resistance in the copper traces. This is a simplified example and it isn't always this easy, but hopefully this gives you an idea of why Forward Voltage Drop is important. Excessive drop in voltage can make your LED lights to burn dimly. If we assume that each LED has a voltage drop across it when illuminated of 1.2 volts, then the voltage drop across all three will be 3 x 1.2v = 3.6 volts. These LED's had a maximum limit of 100mA. 5 = 4.8 + Resistor. So there is .2V across the resistor! Resistor = 0.2. R SERIES = (V S – V LED) / I LED. Note that the LED may glow. If reversed, this is no longer forward voltage but reverse voltage, and the LED will not light up. I LED is the desired current through the LED. V LED is the voltage drop across the LED and. As supply voltage: For molex: 5, 7 and 12 volts Batteries: 1.5 and 9 volts As led forward voltages: Red and green: 2 volts Blue and white: 3.0 - 3.5 volts Led current: 20mA will work for most regular leds. Here, V S is the Source or Supply Voltage. In our simple LED Circuit consisting of a single LED, we have used a 5mm White LED and a power supply of 12V. If we also assume that the three LEDs are to be illuminated from the same 5 volt logic device or supply with …