modified 10 years ago

M10C5

00:35:23

LED data sheet specifications:
Voltage  =  2 Vdc (drop)
Current  = 15 mA

But we have a 5 Vdc supply...

R = (Vs - Vled) / Iled
R = (5 V - 2 V) / .015 A
R = 200 Ohms

Notice that as R ^, the LED gets dimmer
(looks off at ~ 2 K Ohms),
and as R decreases the LED gets brighter,
until we reach ~ 97.5 Ohms, at which point the LED "burns out".  The voltage is still O.K., but the current is 30 mA which is 50% above the LED's spec of 20 mA.

published 10 years ago

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