LED strip light-Design-LED PCB

- Feb 20, 2017-

LED strip light-Design-LED PCB

LED strip light


Variables in strip lighting consist of water resistance, colour, adhesives, choice of SMD, driving voltage, and whether it is constant current or constant voltage layout.

Uncoated LED tape is not considered to have any resistance to water ingress, but may be rated as IP20 for some physical ingress resistance. Such tapes are generally low voltage and safe for skin to touch but can be shorted by fine metal objects. Water resistant strip lighting is covered in a heat conducting epoxy or silicone to protect the circuitry from direct contact with water, and can be rated IP65, IP67, or with suitable sealed connections IP68. Both coated and uncoated LED tapes have a two sided adhesive backing to stick to walls, desks, doors, etc.

The most common design differences are in how individual LEDs are controlled, specifically differences in color and whether or not each LED is addressable.

  • Single Color, non-addressable: Every LED on the strand is a single white colour, typically ranging from 2700K to 6500K in colour temperature, or any of several monochrome colors covering the range of the visible spectrum (generally from 400-700 nanometers in wavelength).

  • Multicolor, non addressable: Each LED is capable of displaying red, green, blue, or all three (white), driven by three input power rails. All the LEDs display the same colour at any one time, but the colour can be manipulated by varying the voltage applied to each of the three power inputs.[citation needed]

  • RGB, addressable: Multiple colours and addresses. Each LED has its own chip meaning they can be individually triggered for chasing, strobing, and colour changing.

LED strip designs are available populated with many different types of SMD, not only in different colours and addressable or non-addressable, by different shapes, sizes, and power levels. The most common types of SMD are: 3528, single colour, non-addressable, very low power; 5050, containing three LEDs allowing for RGB and addressable strips as well as higher power levels; 2835, a newer single-colour SMD having the same surface dimensions as the 3528 but a larger emitter area and a thinner design with an integrated heatsink allowing for higher power levels; 5630/5730, a newer replacement for single-colour 5050 SMDs which can operate at slightly higher power levels and have high efficacy. Less common designs may have 3014, 4014, 7020, 8020, or other SMDs.

LED strip lights most commonly operate on 12 or 24 volts of direct current from a power supply, sometimes referred to as a driver. USB strip lights operate on the standard 5-volt direct current used by USB devices. Mains voltage LED strips are also available. These have the advantages of being usable in much longer single runs without a brightness drop along the length, but are less flexible and heavier due to higher voltage and current ratings and thick coatings for shock safety and high IP ratings in their intended outdoor positions, with limited cut points. No separate power supply is needed, although there must be a rectifier between the mains supply and the end of the LED strip.

The most common PCB designs use multiple parallel circuits consisting of passive dropper resisters in series with a certain number of LED SMDs, to operate at a certain current and power level with the expected input voltage. This design is referred to as constant-voltage and is rather sensitive to small variations in input voltage and to the voltage drop that occurs along long lengths of strip when driven from a single power input. Alternative design is the "constant current" design where each parallel circuit of several SMDs includes a small integrated circuit to provide a fix current to that group of LEDs, within a wide range of applied voltages. This allows the strip to operate at the same power level and brightness along its entire length, or with some variation in the driver voltage.

Any customizations require an LED controller to adjust brightness, colour, or individual LED activity. This can be done with an included controller or customized with a microcontroller.

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