Current Limiting Resistors. R f limits the current when r v is at its minimum setting usually 0 ω which allows maximum current to flow through the led. Now we know the current.
Now we know the current. When current flows through a resistor there is in accordance with ohm s law a corresponding voltage drop across the resistor ohm s law states that the voltage drop is the product of the current and the resistance. Passive resistive components such as resistors or negative temperature coefficient ntc thermistors are simple options with power dissipation and cool down time being their main drawbacks respectively.
The voltage of resistor vr1 is what to look for.
Let s say you are using the led above with a supply voltage of 12v an led forward voltage of 3 9v and a total forward current of 1400ma. The equation for power is. Current limiting resistors are placed in a circuit to ensure that the amount of current that flows does not exceed what the circuit can safely handle. You need to be sure the wattage power rating for your resistor is sufficient for the power being used.
