Introduction: RGB Led Color Mixer

This simple RGBled color mixer uses NO microcontrollers( Arduino - Pic etc ). It controls the brightness of each color channel by varying the duty cycle (On time vs OFF time) by a technique named PWM or pulse width modulation. This results in a very low power dissipation, as leds are either fully on or off. The circuit manages the three channels with only 1 common integrated circuit and 2 transistors.

Step 1: RGB Controller at Work

Picture of RGB Controller at Work

Step 2: Complete Circuit Diagram

Picture of Complete Circuit Diagram

Main components:

IC1: TL084 (quad FET input op-amp)

Q1: BC558 (general purpose PNP transistor)

Q2: BC548(general purpose NPN transistor)

D1-D61N4148 diodes

VR1-VR3 10Kohm Linear potentiometers

LED: RGB common cathode led

Step 3: PUT Oscillator (sawtooth Generator)

Picture of PUT Oscillator (sawtooth Generator)

Step 4: Comparators 1-3

Picture of Comparators 1-3

This in turn determines the time each led will be ON during each sawtooth oscillator cycle, making it appear to be brighter or darker to the eye.

Step 5: Driving RGB LED

Picture of Driving RGB LED

For this demo I am driving the LEDs directly from the OP-amp, but you can drive any power leds, by adding a power mosfet or transistor.

Step 6: For More Details & Waveforms Watch the Video

Step 7:


AndrewS553 (author)2017-08-23


would it be possible to construct something like this but instead of the 3 levels we an app in a smartphone to control the color and intensity?

and also is it possible to use power from a smart phone charging port instead of battery?

thank you:)

guesswho520 (author)2016-01-14

I am slowly learning how to read these. Can you list a total parts list you used in this project?

guesswho520 (author)2016-01-13

I have been looking for a circuit that does not involve an Arduino. Is there a way to see how this was constructed?

simpletronic (author)guesswho5202016-01-13

You will find the circuit diagram in step 2 and also a video in step 6.


JacobT10 (author)2015-07-29

I really would like a quick reply, great project! I have been looking all over the internet and when I see these controllers with arduinos and I cant understand what it could need it for, all it does is vary the power going to pins of the led, a switch could do that. Well, i'm happy I found this, but I have never done any circuitry. Looking at the schematics makes my head hurt, could you possibly do a different schematic that is more wire and component pictures? Dont email it, I dont use email. It would help more than me if you could add that schematic to the project along with pictures. I know I sound like a noob but I really would like to do this!

nqtronix (author)2015-05-24

A single view on the schematics and I've remebered the style: You are the guy with the everlasting LED! Glad to see you again here. It's truely amazing what you are doing with basic components.

Keep rockin' ! :D

simpletronic (author)nqtronix2015-05-24

Hi !

Thanks again, there's a lot more coming, please stay in tune !

diy_bloke (author)2015-05-23

What... no microcontroller but actual discrete components???? I feel like... i am young again :-)

simpletronic (author)diy_bloke2015-05-24

Yeah! no GOTO, MOVLW OR BTFSS... just plain ol' leads you can bend & solder!

( I'll be posting some of the others too ) :-)

tomatoskins (author)2015-05-23

This is awesome! And those sliders look so cool! I honestly never thought to use PWM for mixing colors on an RGB LED.

simpletronic (author)tomatoskins2015-05-23

Great !!

About This Instructable




Bio: Music: my profession for over 40 years... Electronics: my beloved hobby always.
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