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RGB LED Light

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timbro

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Hi!

I am trying to make an led light with 3 knobs for brightness of each led color. My original plan was to just hook a variable resistor to each color. But that seems to me that it may not work properly because of the resistances of having the colors hooked up in parallel (if that makes any sense). I read up some more and found out about PWM's. Im a big noob when it comes to this stuff. What would the easiest way for me to creat this LED light?
 
you could just use a rheostat if simple is what your looking for. but they are basically variable resistors and will work but do sometimes get warm if you pass to much current through them. pwm would work too but is rather more complicated to build
 
hrmm see my friend made a mokup using some linear trim pots and there is this problem that when you dim 1 color the other colors get brighter which i dont want to do unless i absolutely have to. Are there any easy instuctions out there to make a pwm? Ive searched quite a bit and i cant find anything that i can understand.
 
put a resistor on the led's to limit the amount of curent allowed to go to them
 
If the other colors get brighter when you dim one LED then your power supply (or battery) voltage changes with current change. Maybe the power supply is overloaded or maybe the battery is worn out.
Use a voltage regulator.
 
Gayan Soyza said:
See this link but little bit advanced

http://tobe.nimio.info/led_mood_lamp.php
It is messed up. The poor PIC is driving the dead short of the bases of transistors without any current-limiting resistors. Many people on the author's forum complained that their PIC got very hot then stopped working.

A similar circuit is a project at Electronics-Lab and current-limiting resistors were added that have a value way too high. Then the transistors do not saturate and get very hot and the expensive 3-colours LED doesn't get very bright.
 
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