Find the “Led Voltages By Color” by scrolling to the bottom
Below you can find a table that you can use as a guidance on LED Voltages when you don’t have a datasheet at hand.
It’s probably good to use the lower voltage value for calculation purposes, and if the LED light is not bright enough, use a lower value resistor.
This way the risk of damaging the it is lower.
Consider this example:
Assuming lower value:
- VCC = 5V
- assume 1.6V for red LED
- voltage across resistor = 5V – 1.6V = 3.4V
- resistance of limiting resistor = 3.4V / 0.02A = 170 Ohm
Now if the real LED voltage is not 1.6V but 2V, this means:
- real voltage across resistor = 5V – 2V = 3V
- real current through resistor = 3V / 170 Ohm = 0.017A = 17mA, lower than the maximum rating of 20mA, so no damage occurs.
- the led will be dimmer but now you can choose a resistor with a higher value to make the LED brighter
Assuming higher value:
- VCC = 5V
- assume 2V for red LED
- voltage across resistor = 5V – 2V = 3V
- resistance of limiting resistor = 3V / 0.02A = 150 Ohm.
Now if the real voltage over the led is not 2V, but 1.6V for your LED, this means:
- real voltage across Resistor = 5V – 1.6V = 3.4V
- real current through resistor = 3.4V / 150 Ohm = 0.022A = 22mA, which is higher than the LED’s maximum current rating, therefore some damage may occur in the long run.
Of course, ideal would be to have the datasheet at hand but if one is not available, feel free to use the led voltages in this table.
Guidance table on LED color to rated led voltage
(these values are not guaranteed and apply to common Light Emitting Diodes, but not to *all* leds, therefore please consult your led’s datasheet if available)
Please take note that there are Resistor LEDs out there. For example, you may find a LED that is rated for 5V or 12V. And these may also be rated for a lower current, such as 10mA.
Needless to say, the table below does not apply to such LEDs, but only to regular LEDs, without built-in resistors.
|Color||Voltage drop at 20mA||Wavelength (nm)|
|Infra-Red||Less than 1.63V||Λ > 760|
|Red||Between 1.63V and 2.03V||610 < Λ < 760|
|Orange||Between 2.03V and 2.10V||610 < Λ < 760|
|Yellow||Between 2.10V and 2.18V||570 < Λ < 590|
|Green||Between 1.9V and 4.0V||500 < Λ 570|
|Blue||Between 2.48V and 3.7V||450 < Λ < 500|
|Violet||Between 2.76V and 4.0V||400 < Λ < 450|
|Ultraviolet||Between 3.0V and 4.0V||Λ < 400|
|Purple||Between 2.48V and 3.7V||–|
|White||Between 2.8V and 4.2V||Broad spectrum|
This table was created with data available on Wikipedia, at https://en.wikipedia.org/wiki/Light-emitting_diode
You can find more detailed information about Light Emitting Diodes, how to visually recognize their pins and how you can quickly create a simple circuit in this article: LED – Light Emitting Diodes – The basics