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### Topic: two leds, one output? (Read 1 time)previous topic - next topic

#### danimath

##### Apr 13, 2012, 05:48 pm
Hi all,

I'm getting old  I forgot the proper way, and the search of these words gives too much results. I want to drive two leds with one PWM output pin (left eye and right eye of my evil spider  ]. Serial or parallel? (For the latter: one or two resistors?).

best regards
Andreas
http://danimathblog.blogspot.com

#define true '/'/'/'
#define false '-'-'-'

#### udoklein

#1
##### Apr 13, 2012, 06:14 pm
If the forward voltage is low enough --> serial. If it is to high --> parallel with separate resistors.

#### danimath

#2
##### Apr 13, 2012, 06:38 pmLast Edit: Apr 13, 2012, 06:47 pm by danimath Reason: 1
Brett vorm Kopf (plank in front of head  . Standard LED, U_F = 2.25 V; this gives the forward voltage of 4.5 V. So: 5 V - 4.5 V = 0.5 V; R = U/ I is here R = 0.5V / 10 mA = 50 Ohm. Is this correct? (Just to be sure).

Thanks, Danke, merci, gracie
Andreas
http://danimathblog.blogspot.com

#define true '/'/'/'
#define false '-'-'-'

#3
Quote
Is this correct?

Yes

#### danimath

#4
##### Apr 14, 2012, 10:46 am
Thanks, Danke, merci, gracie Mike! I've done this stuff 40 years ago, so the knowledge got a little bit rusty

Andreas
http://danimathblog.blogspot.com

#define true '/'/'/'
#define false '-'-'-'

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