LED Indicator Application Design

Release Date:

2022-01-27

　　LED technology is becoming increasingly mature. LED indicator light They can be found in most devices and circuits. So, what should we pay attention to when selecting and designing LEDs in practice? LED technology encompasses a wide range of applications; this article focuses on the key parameters to consider when choosing basic LED indicator lights, along with design examples. In subsequent articles, we will cover the selection and design of specialized LEDs, such as UV LEDs. For now, let’s explore the application design of LED indicator lights!

　　

LED indicator light

 

　　 LED indicator light Main parameters

　　The dominant wavelength is the peak wavelength. The light perceived by the human eye is not entirely identical to the light detected by machines; therefore, two wavelength metrics are used: dominant wavelength and peak wavelength.

　　Peak wavelength: the wavelength corresponding to the region of maximum spectral luminous intensity or radiant power.

　　Dominant Wavelength: The dominant wavelength is the wavelength of the primary light emitted by the light source that corresponds to the color visible to the human eye. LED indicator

　　In general, these two parameters do not differ significantly. When making a selection, the primary consideration should be the application scenario. For optical devices, where wavelength identification is required, the choice should be based on the peak wavelength. If the device is used for indication purposes, since the receiver is a human, the dominant wavelength is usually the more important factor to consider.

　　Color and wavelength are in a one-to-one correspondence. When selecting a replacement LED material that matches a previously used color, you can directly compare the wavelength parameter. If the wavelengths match, the colors will also match. Below are the typical wavelength ranges corresponding to common colors.

　　Luminous intensity (measured in millicandelas, mcd) is a quantity that measures the strength of light emitted by a source; it represents the brightness of light that a device can detect. LED indicator lights

　　In practical applications, the human eye’s perception of light varies with wavelength. For LEDs emitting the same amount of radiant energy, red light appears much brighter than green light. In actual design, it may be necessary to use LEDs of different colors simultaneously. To ensure uniform brightness across all LEDs, one can appropriately select green LEDs with higher luminous intensity.

　　Parameter 3: Forward Voltage, Forward Current

　　An LED is a type of diode; under normal forward-bias conditions, the forward voltage Vf can be regarded as the rated voltage required to produce light. The forward operating current If can be regarded as the rated current needed to achieve luminous emission. In general, the higher the forward operating current, the greater the LED’s brightness.

　　The larger the forward current If, the higher the temperature, and the shorter the LED’s lifespan. When the ambient temperature is high, to extend the LED’s service life, it is recommended to reduce the forward current. Many manufacturers provide curves in their datasheets that correlate temperature with the rated forward current.

　　Packaging mainly comes in two types: patch and through-hole.

　　Generally speaking, the patch occupies a slightly smaller footprint. The following are the relevant parameters for the patch package. LED indicator

　　While you can also make your selection based on size, the length and width shown in the figure below primarily refer to the dimensions of the patch package.

　　LED Design Example

　　Below is a simple LED indicator light design example. As an illustration, consider the QTB QBLP631-AG LED, which has a forward voltage of 2.0 V and a forward current of 20 mA. The goal is to design an LED lamp with adjustable brightness. A 5-V power supply or battery is available, and the LED’s forward current is required to be adjustable between 10 mA and 20 mA. To achieve this, a variable resistor is connected in series. When the current is 20 mA, the LED is at its brightest; at this point, the resistor value is (5 V − 2 V) / 20 mA = 150 Ω. When the current is 10 mA, the resistor value becomes (5 V − 2 V) / 10 mA = 300 Ω, and the LED’s brightness drops to about half of its maximum. The circuit diagram is shown below.

　　LED dimming design

　　High-power LED lighting has traditionally been compatible with TRIAC dimming. Prior to the widespread adoption of LED technology, TRIAC dimming was primarily used for incandescent and halogen lamps. When LEDs replace these traditional light sources, TRIAC dimming remains largely interchangeable. This solution is commonly employed in residential lighting applications.

　　A triac can be regarded as two thyristors connected in inverse parallel. Without current, the thyristor turns off automatically. When a gate current is applied, the thyristor turns on again. By controlling the gate current through an RC network, dimming can be achieved.

　　In the practical application of LEDs, pulse-width modulation (PWM) is widely used for high-quality, high-reliability LED applications. PWM control finds extensive use across numerous fields, ranging from measurement and communication to power control and conversion.

　　The human eye has difficulty perceiving noticeable brightness changes when the frequency reaches 100 Hz. A microprocessor’s digital output is used to control an analog circuit. The microprocessor outputs a square wave at a specified frequency, and by adjusting the duty cycle of the high and low levels, the brightness of the LED can be controlled. In PWM control, the voltage typically used is the forward voltage specified in the device datasheet.

　　Summary of Experience

　　When selecting and designing LED indicator lights, life insurance companies must consider key parameters to ensure proper selection.

　　Wavelength: Wavelength corresponds to color.

　　Luminous intensity: On LEDs with the same radiant intensity, red light appears much brighter than green light. LED indicator.

　　Forward voltage and forward current: depend on the driver design.

　　The following are the primary design considerations during the design phase of the LED indicator light system.

　　By using a simple design, connecting a resistor in series with the power supply is sufficient to produce light.

　　Traditional home lighting can consider triple dimming.

　　PWM control can be employed for several high-quality, high-reliability LED APP applications.

　　The above is an overview of LED indicator application design. For more information, please feel free to contact us at any time!

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