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Topic: People hate resistors for their LEDs (Read 4 times) previous topic - next topic

westfw

I used 1k for nearly all my "indicator" LEDs.  With modern LEDs, that's plenty bright, and it's pretty-much always safe (<5mA)  1k resistors are useful for LOTS of things!
Now, when you get to illumination rather than indication, you can start worrying about "correct" LED resistors.

EVP


CrossRoads

I just remember the formula
(Vs - Vf)/.02 = resistor
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

GoForSmoke

EVP; I bookmarked that page twice and Karma'd you once.

Crossroads, I never tried but can I get Vf using a meter on the led?

One way I can get at least close is get the led in bright light and see the V it generates.
I find it harder to express logic in English than in Code.
Sometimes an example says more than many times as many words.

CrossRoads

Use 5V and 270-330-470 ohm resistor, something in that range, measure Vf across the LED.
You cannot measure it without current flowing.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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