Making an RGB LED Colour Slider Using Bare Paint

In this tutorial we will build a physical RGB (red, green, blue) LED (light emitting diode) colour mixer using Bare Conductive Paint. Each RGB LED has three internal light emitting diodes (LEDs) for each of the colours - red, green and blue. Further there is a lead to connect and control each of these internal diodes. Thus you can mix these three and get a whole range of new colours. The diagram below shows what one would commonly find inside a RGB LED.

Step 1: RGB LED Internal Diagram

You can see that pin 2 is the three internal LEDs negative lead or cathode and 1, 3 and 4 are each of their respective positive leads or anodes. We are going to physically control the RGB LED by making Bare Paint Potentiometers for each of its positive leads instead of using static resistors. Thus by altering the resistance we will ultimately change the current flowing into each diode and affect its brightness. This is a fairly crude way to control LEDs. There is a more elegant way to do this using an Arduino and PWM (pulse width modulation). We will cover this in another tutorial.

Step 2: Components

The image below shows a RGB LED with a common cathode. This simply means that the 3 internal LED's share a common lead and this lead should be connected to ground. Ground is a name electronically minded folk use as the reference point that all the other voltages are measured from, or a common return path for electric current. In our circuit ground simply means the negative terminal on the 9V battery.

Step 3: What You Will Need:

What you will need for this tutorial:

Bare Paint
Paint Brush
Paper
RGB LED (common anode) - if using common cathode please modify circuit diagram
Resistor
Jumper Wires
Breadboard
Paperclip Wires and Paperbinder Wires (use stranded wire, solder and basic stationary components to make these highly useful connectors)
Battery and Battery Clip


9V Batteries - Jameco
Battery Clip -  Jameco
Stranded Wire -  Jameco
Soldering Kit -  Jameco
Paper clips - Any stationary shop
Resistors UK:  Sparkfun
Breadboard -  Sparkfun
RGB LED -  Sparkfun

Step 4: Materials

The first step is to gather the appropriate materials mentioned above:

1. A jar of Bare Paint, paint brush and paper, or a Bare Paint Pen

2. An RGB LED common cathode

6. 3 Paperclip wires and 3 slider wires

7. Solder-less breadboard and some jump wires

8. Some paper or other non-conductive material to apply the Bare Paint

9. A 9V Battery and a battery clip with wires

Step 5: Painting the 3 Variable Resistor Strips

The most basic way to think of a potentiometer, or variable resistor in this case, is a long piece of conductive material that can be tapped off with a slider at different lengths. In our case the material is Bare Paint and our slider is simply a long piece of wire. Depending on what length you want to 'tap off' from the painted line you can vary the resistance across the potentiometer. The longer the painted piece you 'tap off' the higher the resistance.

Taking your pot of Bare Paint, lavishly paint three lines across a piece of paper or another non-conductive surface. Make sure to bring the lines close to the edge as we will need to connect to the paint using electrical wire and paperclips. Once you have painted your lines, leave them to dry for several minutes. You can leave the paint under a hot light to speed up the drying process.

Step 6: Making Paperclip Wires and Sliders for Your Painted Variable Resistor

Taking a piece of stranded wire, cut 3 sensible lengths of about 15 - 20 cm each and strip the ends with a pair of wire cutters or wire strippers. Next, connect the paperclips to one end of each wire. Have a look at this tutorial on how to make paperclip wires in more detail. You will use these paperclip wires to connect from your breadboard to your painted variable resistors.

Next, cut three lengths or about 40 - 50 cm each; you'll need the extra length for freedom of movement. Strip the ends and this time solder paper binders onto one of the ends of each wire. The other end will be placed on the breadboard.

Step 7: Breadboard Schematic

Now that you have all the separate pieces ready we can connect everything together on the breadboard. Make sure to double-check your connections using the breadboard schematic below.

Step 8: Testing the Red Green and Blue Internal LEDS

Everything should now be connected as shown in the photo above. To test the internal LEDS, touch the slider wires on the different strips of paint. Each slider wire should correspond to one internal LED.

Step 9: Test.1

Touch the RED Slider

Step 10: Test.2

Touch the GREEN Slider

Step 11: Test.3

Touch the BLUE Slider

Step 12: Now for Mixing

It's time to experiment and see what colours you can generate. Have fun and send us you photos and comments.

If you have any questions please email them to [e-mail], and don't forget to submit your own projects to [e-mail]