The 5mm infrared (940nm) LEDs are encapsulated in a transparent colored resin dome whose purpose is to protect the light emitter, it contains three pieces: reflector cup, semiconductor, and conductive wire. Two legs extend below this dome: the longest is of positive polarity and is called the anode, the shortest is of negative polarity and is called the cathode. These pins will indicate the way in which the LED should be connected to the circuit.

These LEDs are the best known within the range of high luminosity LEDs. 5mm IR LEDs are available in two formats: 850nm and 940nm. You should always take into account that the "nanometers" are the frequency of the light emitted by the LED, the lower this frequency, the greater the chances of being seen by the human eye.
They have more specific applications than colored LEDs: they are widely used for security applications, that is, security cameras, CCTV, night illuminators, peripheral lighting for security cameras, and night vision, among others.

How do they work?

LEDs can be used in three different ways:

• Individual: direct LED power from the power supply, either by means of a regulated source or with the use of resistors or regulators. The desired voltage must be supplied to the LED within the working values.

• Parallel configuration: powering a group of LEDs connecting all the anodes together and all the cathodes together, using the required voltage regulated by a single resistor in series.

• Series configuration: powering a group of LEDs connected sequentially. The number of LEDs to be used per series will be limited by the voltage delivered by the power supply. In most cases, a resistor is required to compensate for the differences in supply voltage per series of LEDs, being able to carry out different series in parallel with the same power supply.