18th February 2019, 11:48
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#7
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This is my second home
R75 Saloon.
Join Date: Feb 2009
Location: France/or Devon.
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Quote:
Originally Posted by daznkel
Typically the forward voltage of the led will be in the range of 2.8-3.6V and the forward current 20-30mA. These values, as already mentioned, vary according to many things, but colour is one of the factors.
So if you assume a 12V supply, from the car. A forward voltage of 3.2V and a forward current of 25mA, you would be looking at a 390 Ohm resistor.
(12V-3.2V)/0.025 Amps=352 Ohms preferred value resistor = 390 Ohm. 
To reduce the brightness, assuming you are going to keep the forward voltage the same, the current has to be reduced, by increasing the resistance. |
So can you build in a variable resistor. I notice that house lighting LEDs can have a variator switch now. |
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