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What resistor???

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audioguru

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The resistor in series with an LED limits the current, it does not drop the voltage. An LED has its own voltage and could be powered from thousands of volts if the current-limiting resistor is calculated correctly.

If you connect fifteen 3.5V LEDs in series then you need 15 x 3.5= 52.5V (or more) for them plus about 5V for the single current-limiting resistor.
I don't think you have 57.5V or more.

Why did you make this new thread? It has no circuit description and no schematic so we don't know what you are talking about.
 

audioguru

Well-Known Member
Most Helpful Member
A white LED can have its current limited by a single resistor from a supply of 4.5V if you know the voltage of the LED (it is a range of voltages from 3.2V to 3.6V) and how much current you want in it.

Since you did not say what is the max allowed current in the LED, the amount of current you want in it or the voltage of the LED then we cannot help you simply calculate the value of the current-limiting resistor.
 
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