Contents
Do I need a resistor for a 3V LED?
Many 3V LEDs are not exactly 3V, they may range a bit like 3.0-3.2V. The idea of a resistor is to limit current. Even if you match a LED exactly to a voltage, it may draw more than the LED current rating. The resistor is just a safety feature to save the battery (and LED) from a short circuit current overload.
Do I always need a resistor with an LED?
An LED (Light Emitting Diode) emits light when an electric current passes through it. The simplest circuit to power an LED is a voltage source with a resistor and an LED in series. Such a resistor is often called a ballast resistor. If the voltage source is equal to the voltage drop of the LED, no resistor is required.
How can you limit current through an LED?
An LED must have a resistor connected in series to limit the current through the LED, otherwise it will burn out almost instantly. VS = supply voltage. VL = LED voltage (2V, or 4V for blue and white LEDs). The LED current must be less than the maximum permitted for your LED.
What resistor do I need for a 3 volt LED?
Basics: Picking Resistors for LEDs
| Power Supply Voltage | LED Color | Resistor (calculated) |
|---|---|---|
| 3 V | Red, Yellow, or Yellow-Green | 48 Ω |
| 4.5 V | Red, Yellow, or Yellow-Green | 36 Ω |
| 4.5 V | Blue, Green, White, or UV | 48 Ω |
| 5 V | Blue, Green, White, or UV | 68 Ω |
What kind of resistor is needed for 3.3V LEDs?
Indicator LEDs are 20-50 mA. You then use an LED resistor calculator the find the value of the resistor. A red indicator LED with a 220Ω resistor draws about 13 mA at 5V. 13 mA at 3.3V would use a 91.3Ω (1%) or 100Ω (5% 12mA) resistor Thanks for contributing an answer to Electrical Engineering Stack Exchange!
How much current does a 3.3V indicator LED draw?
A very common current for LEDs used in lighting is 65mA. Indicator LEDs are 20-50 mA. You then use an LED resistor calculator the find the value of the resistor. A red indicator LED with a 220Ω resistor draws about 13 mA at 5V. 13 mA at 3.3V would use a 91.3Ω (1%) or 100Ω (5% 12mA) resistor
Is it safe to power LEDs with 3.3V?
You cannot safely power most LEDs with a 3.3V source when the source can supply more current than the LED’s capacity. Two characteristics of the LED need to be known to calculate the resistor. If the current output of the 3.3V source is less than the LED’s maximum, then it is safe.
Can a 5 volt led be driven without a resistor?
If we want to use it at 5 Volt, we have to use a resistor to dissipate the remaining 2.9 Volt. To compute the resitor, we use: R = V / I = (5 Volt – 2.1 Volt) / 25 mA = 116 Ohm. To be safe we use a 120, or better, 150 Ohm resistor. That way we don’t drive the LED near it’s maximum rating.