Yes, you typically need a resistor for each color channel (Red, Green, and Blue) of an RGB LED to limit the current and prevent damage to the LED and other components in the circuit. RGB LEDs are composed of three individual LEDs, one for each color channel. Each color LED has a specific current rating that should not be exceeded.
When the button is not pressed, the input pin is pulled high. The value of the pull-up resistor controls the voltage on the input pin. For condition 1, you don't want the resistor's value too low. The lower the resistance, the more power will be used when the button is hit. You generally want a large resistor value (10kΩ), but you don’t want
Thus, yes you do need a resistor for your external LED. Only the very early boards had a resistor on pin 13. The numerous tutorials out that there that still claim pin 13 has a resistor are just flat out wrong. No recent (well over 2 years now) Arduino has a built-in resistor on Pin 13.
Or do I say that the red LED needs less voltage than the green LED to glow as brightly, and the resistor soaks up voltage because of V=IR? You could say, the red led needs less voltage for the same amount of current because its voltage drop is lower than a green led.
Most LED's are DC voltage and are in the 2-3 volt range. Which means you will need to reduce the voltage down to meet the LED's requirements. Most people use a resistor. Thats all thats needed. No Ballast no nothing. unless you get into some Hi-perf LEDs then theirs something known as and led driver but thats another story.
If you connect an LED to an Arduino pin, you absolutely need to include a series resistor. The reason for this is, without it the current will not be limited (except by physics of course). Since the ATmega328P can source up to 40mA you'll either burn up your LED or blow your output driver, whichever happens first.
24V/0.2A = 120Ω, which is the finished resistance, not the initial resistance. The initial resistance is 16V / 0.2A = 80Ω. conveniently this is 40 less than the finished resistance confirming your first calculation. Go out and buy a 2W 39Ω resistor. 39Ω is a standard size, and will be close enough to 40 for your task.
Resistors in Light Emitting Diode (LED) Circuits. 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.
What to do first. Firstly, you must ascertain what bulb types your vehicle uses. For interior lights, this is usually as simple as prying off the clear plastic light covers and pulling the bulb out – close the doors or turn the lights off first so you don’t burn yourself! You’ll then need to inspect the bulb to work out what type they are.
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do i need a resistor for led
