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

Step 2: 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)

Step 4: 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

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:

Comments

[Guy17652]

Also off of IC1, is there supposed to be a connection to pin #14 or is it just unconnected?

[Guy17652]

Hi, I really want to build this circuit but I’m still relatively new to reading schematic and mostly just don’t know as much electronics terminology yet. I’m wanting to use LEDs similar to these:

https://www.sparkfun.com/products/8718

Should I use 1 Watt or 3 Watt? And is it necessary to add a power MOSFET or transistor like you mentioned in step 5 to power them or would they be alright to just put in directly like you did in the video? If the MOSFET or transistor is necessary would you be willing to provide some guidance for that? Thanks so much!

[AndrewS553]

Hi,

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]

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

[guesswho520]

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

[simpletronic]

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

greetings!

[JacobT10]

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]

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]

Hi !

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

[diy_bloke]

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

[simpletronic]

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

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

[tomatoskins]

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

[simpletronic]

Great !!