Can anybody help me make a LED backlight? Using 5mm LEDs giving off 3.0v 3.2v, using 200 ohms resistors, and a USB?


frollard5 years ago
most 5mm leds use 20mA current...

use an led wizard if you don't want to bother with the math:
http://led.linear1.org/led.wiz

usb is 5 volts

the voltage drop is about 3 volts (per your question)

and the number of leds is ...however many you want. Because 3 only fits into 5 one time, you can't have series strands. You must drive EACH led with a resistor on each (or risk burning them out prematurely).

The wizard says to put each led in series with a 100ohm resistor based on these numbers.
That's strange
https://www.instructables.com/answers/How-can-I-setup-5mm-leds-whiteblue-30-or-32-m/

You asked exaclty the same question, and I gave you exactly the same answer.....

Steve