fyrstormer
Banned
Looking for some "close enough" internal resistance values for 5mm thru-hole LEDs
In my RC hobby, I make frequent use of old-fashioned 5mm and 3mm thru-hole LEDs running at low power, because they're only being used for illuminating the vehicle so I can see where it's going at night, not for lighting up the path in front of it. The power supply is regulated by the RC electronics, generally to a fixed voltage of 6V, so I can get away with using simple resistors as current-limiters for the LEDs so they don't burn out. The formula of
Rrequired = (Vsupply - Vforward) / Itarget
is easy enough, but I'd like to factor-in the LEDs' Rinternal as well, so I can subtract it from Rrequired.
I know ideal LEDs have no internal resistance, but I also know real LEDs are not ideal LEDs, and at the low amperage levels I'm working with (40mA for white LEDs, 10mA for yellow/orange/red LEDs), the LED's internal resistance becomes a significant factor.
If I were really motivated, I could rig up some electronics to measure the LEDs' actual internal resistance, but I'm not that motivated. What I'd like instead is some "close enough" estimates of the typical internal resistance for red (1.6Vf), orange (2.0Vf), yellow (2.2Vf), and white (3.2Vf) LEDs, so I can plug them into my resistor-calculating spreadsheet. Can anyone help me with this?
In my RC hobby, I make frequent use of old-fashioned 5mm and 3mm thru-hole LEDs running at low power, because they're only being used for illuminating the vehicle so I can see where it's going at night, not for lighting up the path in front of it. The power supply is regulated by the RC electronics, generally to a fixed voltage of 6V, so I can get away with using simple resistors as current-limiters for the LEDs so they don't burn out. The formula of
Rrequired = (Vsupply - Vforward) / Itarget
is easy enough, but I'd like to factor-in the LEDs' Rinternal as well, so I can subtract it from Rrequired.
I know ideal LEDs have no internal resistance, but I also know real LEDs are not ideal LEDs, and at the low amperage levels I'm working with (40mA for white LEDs, 10mA for yellow/orange/red LEDs), the LED's internal resistance becomes a significant factor.
If I were really motivated, I could rig up some electronics to measure the LEDs' actual internal resistance, but I'm not that motivated. What I'd like instead is some "close enough" estimates of the typical internal resistance for red (1.6Vf), orange (2.0Vf), yellow (2.2Vf), and white (3.2Vf) LEDs, so I can plug them into my resistor-calculating spreadsheet. Can anyone help me with this?
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