LED Brightness
The brightness of an LED is determined by a number of factors.
- The quality of the material
- Voltage level and current through the LED
- Is the LED an ultrabright, and this is a purchase option
For this tip, we will just work with a stock standard LED, and the context is that you bought a large quantity and the odd couple doesn't "glow" or illuminate properly.
When the current passes through the lead frame, this generates a small level of illumination. This is then picked up by the lens and concentrated vertically. This explains why from the side or a lower angle of observation it is harder to tell if an LED is illuminated, especially for certain colours. Green and Yellow/Orange for example tend to be harder to see, however, a RED led is fairly visible.
The quality and clarity of the materials used in the molding process do have an effect on the light intensity. If you purchase high-quality LEDs, you will notice that the LED has a glass-like translucence that you can see through. However, lower-quality LEDs are more clouded and solid.
When you select your resistor, ideally you would only want sufficient current to flow through the LED. For this to work a minimum of 1.8 Vdc at ~15mA works for most LEDs. To increase that brightness, you can increase the voltage across the LED or you can adjust the resistor value.
If the voltage across the LED is too high it will grow very brightly and then "pop" ie the wire bond will overheat and evaporate rendering the LED useless.
In your circuit, the resistor chosen may have a 20% tolerance on the value. While this is fine for a single LED or two or three if you were clustering LEDs the effect of that tolerance would become more noticeable. You will notice that the color and light intensity consistency across your installation will differ, and be very noticeable if LEDs are clustered together.
To reduce this, two actions can be taken.
- Always ensure to purchase a quality LED, with a clear translucent lens
- Use resistors with a lower tolerance for example 5% or 1%. While this may be more expensive, inconsistencies in visual appearance will ruin the effect, especially when an observer notices.
Because an LED uses nominal current, a designer may often disregard the cumulative effect of using many LEDs together, or they may use the wrong values in their calculations
This often happens when LED light strips are used. Care is not taken to use a power supply that can run the strip based on the watts per meter specification. This can result in the output voltage of the power supply build pulled down, and poor performance of the LED array as a whole.
Lighting and Light control remains a key area of the application of electronics. LED lighting has slowly taken over from incandescent, fluorescent, and other lighting technologies.
