# Does power source amperage matter when using resistor to limit LED current?

I'm using a typical 3.2v LED and I want to power it from a 5V DC 1amp switching power supply. Can I use a 300ohm resistor to safely power the LED the same way that I would if I was powering it from an Arduino pin, or does the higher current potential of the power supply make this not possible? From what I understand, if the LED voltage drop is 1.8v and it specs are 3.2V typ. 3.5V max @ 20mA, then

5v - 1.8v = 3.2v and 3.2v / .02ma = 160ohm is absolute minimum value for the resistor. Nowhere does the potential current from the 5v power supply make a difference, correct?

Can I use a 300ohm resistor to safely power the LED the same way that I would if I was powering it from an Arduino pin,

Yes.

Nowhere does the potential current from the 5v power supply make a difference, correct?

Correct.

Grumpy_Mike: Yes. Correct.

Thank you!

Commonly quoted alternative example.

My power points are rated at 240 Volts 10 Amps. Does this mean it is unsafe to plug in a 10 Watt LED bulb which we calculate will require only 1/24 of an Amp?