3mm LED Diodes – Red, Orange, Yellow, Green, Blue or White – Green

An LED is a small light that runs from a low DC voltage. It only lights when current flows one way through it, so it has to go in the right way round, and it needs a resistor in series to set its current. These are standard 3mm round-top through-hole LEDs with short legs, in six colours. Red, orange, yellow, green and blue have a lens tinted the same colour as the light, so you can tell them apart in the parts drawer and the colour still shows when they are off. White has a water-clear lens. The green is a yellow-green (568 to 570nm), the classic indicator green, rather than the deeper emerald green of a 525nm LED.

Use them for power and status lights, Arduino and ESP32 output tests, panel indicators in a 3mm hole, or teaching kits. The 2.54mm lead spacing plugs straight into a breadboard and fits standard 0.1 inch PCB pads. They are sold singly with a minimum of 10 per colour. Each LED needs its own resistor, which is not included; the 600-piece resistor kit has every value given below. If you would rather skip the resistor and the soldering, the 3mm pre-wired LEDs come with the resistor and 20cm leads already fitted for 5V or 12V. For a bigger 5mm lens, see the 5mm LEDs.