Contents
Why do you need to add a resistor with an LED?
An LED (Light Emitting Diode) emits light when an electric current passes through it. The ballast resistor is used to limit the current through the LED and to prevent excess current that can burn out the LED. If the voltage source is equal to the voltage drop of the LED, no resistor is required.
Which resistor should I use with my LED?
LEDs typically require 10 to 20mA, the datasheet for the LED will detail this along with the forward voltage drop. For example an ultra bright blue LED with a 9V battery has a forward voltage of 3.2V and typical current of 20mA. So the resistor needs to be 290 ohms or as close as is available.
How to calculate the resistor for an LED circuit?
To calculate the resistor needed for a simple LED circuit, simply take the voltage drop away from the source voltage then apply Ohm’s Law.
How is the current through a led measured?
I LED is the current through the LED *, measured in Amperes (Amps/A), and R is the resistance, measured in Ohms (Ω). * The current through the circuit is constant so ILED is also the current through the resistor. This calculator is based on the Ohms Law Calculator, but takes into consideration the voltage drop from the LED.
How does a resistor add to the impedance of a speaker?
Always make sure the speaker or resistor wire is fully covered & not exposed. A resistor connected in series simply adds its resistance to the speaker impedance rating. (Ex.: A 4 ohm resistor plus a 4 ohm speaker = 8 ohms total). 2. Using resistors to decrease the total speaker impedance load
What is the current through a V led?
V LED is the voltage drop across the LED, measured in volts (V), I LED is the current through the LED *, measured in Amperes (Amps/A), and R is the resistance, measured in Ohms (Ω). * The current through the circuit is constant so ILED is also the current through the resistor.