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Author Topic: Connecting many RGB LEDs to same PWM pins?  (Read 4406 times)
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Ow dear, now I am confushed  :-/ But thnx for the replies!!

Why I should I use another transistor to PWM the BC327?
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Why I should I use another transistor to PWM the BC327?

because you use +12V. for common cathode tri-colors LED driver and control logic level from Arduino is 0 to 5v.
then driver can't drive directly by single transistor, NPN + PNP cascade circuit will translate control level and made circuit work.

if change driver voltage to +5V., You can use only PNP circuit part but action will be opposite (active logic LOW)
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 :o Thnx for the expleantion, I understand it (a bit)

So, when I PWM an transistor with 1/2 the ammount off volts as the collector recieves, the emitter shall output 1/2 volts that the emitter is recieveing .
(this is lost in translation)

Sounds logic.
« Last Edit: November 07, 2007, 06:17:45 am by Westbam » Logged

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So, when I PWM an transistor with 1/2 the ammount off volts as the collector recieves, the emitter shall output 1/2 volts that the emitter is recieveing .

PWM still digital pulse signal (0 or 5 Volt only) but "Duty cycle" change is effect to average "Output power"
then the switch mode transistor circuit still work on PWM signal

this page is good example to see what different on 10% 50% and 90% PWM signal,
http://www.netrino.com/Publications/Glossary/PWM.php

if circuit is active HIGH,
LED will ON while logic HIGH
and OFF if LOW
but PWM is blinking at high frequency, then human eye will see the "dimmed" light instead of blinking
at PWM 100% (255 in value) is always ON and most bright and dimmed if lower %PWM
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