The LED and R1 are connected across about 42VDC. The LED drops about 2V so that leaves about 40V on R1 so the LED current is 40/2700 ~= 15mA. Different color LED have slightly different voltage drops but it is a small part of the total voltage so it has little effect. 15mA may be too bright for a modern LED so you may want to increase the value of R1 to maybe 10K. led - Calculating forward voltage for a string of fairy lights: multimeter shows "1" - Electrical Engineering Stack Exchange
It appears that the OP isn't entirely aware of how to use LEDs.
Most LEDs fall into a range of operating voltages between about 1.7V and 2.7V depending on their colour and composition.
In this application this is "largely" immaterial.
What is important is the current that will be flowing through the LED.
You need to know the "raw" DC voltage that is to be applied across the LED.
In this case that will be approximately 30V x 1.4142 = 42V DC.
The maximum current that can be allowed to flow through the LED should be set to be between about 5mA and 10mA.
If VLED = 1.7V and ILED = 5mA.
R = (42 - 1.7) / 5mA = 8.06 K Ohms.
This is not a common value so we choose the closest value. In reality anything between 4K7 and 10K would be fine.
If VLED is 2.7V and ILED = 10mA
R = (42 - 2.7) / 10mA = 3.9K
Again anything around this value will be OK.
I hope this illustrates that the VLED is largely immaterial, it will, within limits, only slightly affect the current flowing through the LED.
Most LEDs fall into a range of operating voltages between about 1.7V and 2.7V depending on their colour and composition.
In this application this is "largely" immaterial.
What is important is the current that will be flowing through the LED.
You need to know the "raw" DC voltage that is to be applied across the LED.
In this case that will be approximately 30V x 1.4142 = 42V DC.
The maximum current that can be allowed to flow through the LED should be set to be between about 5mA and 10mA.
If VLED = 1.7V and ILED = 5mA.
R = (42 - 1.7) / 5mA = 8.06 K Ohms.
This is not a common value so we choose the closest value. In reality anything between 4K7 and 10K would be fine.
If VLED is 2.7V and ILED = 10mA
R = (42 - 2.7) / 10mA = 3.9K
Again anything around this value will be OK.
I hope this illustrates that the VLED is largely immaterial, it will, within limits, only slightly affect the current flowing through the LED.
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