How to mix colors using red, green, and blue, or RGB. You'll also learn how to make a paper circuit with simple switches.
The amount of voltage (or energy) going through each leg of an RGB LED determines its final color.
This is a kids circuit activity that teaches more than just wiring and LEDs - this project looks at how we mix primary colors to make the entire rainbow. The primary colors, red, green, and blue, make up a colorset called RGB. It;s not a big leap to notice that the R stands for red, the G for green and the B for blue.
We've come up with a project that will let you mix in varying amounts of red, green, and blue by mixing voltages to various legs in an RGB LED.
If you find yourself wondering what is RGB or why we use RGB color space for cameras and screens you should check out our explanatory "What is RGB?" post!
You want to keep the black around the keys as this will make it easier to align your keys at the end, and make a nicer looking finished piano.
There are three keys with a black dot on them. Surrounding the black dot are dotted lines. Cut along the dotted lines to that these three keys can be bent up slightly. These three keys will ultimately make the switch to each color leg. When the key is pressed the circuit will be complete for that color and it will light up.
For a switch to work, it needs to be able to open and close a circuit. Here, when the key is not pressed there will be a gap in the circuit. You can see this gap on the piano part of this template. When you press a key the copper tape on the back of each key will close the gap and allow the electrons to flow through the circuit, lighting up the LED!
Now that the keys to your piano are done you are ready to move to the next piece. Cut around the black of the piano template.
There are 5 lines of copper tape for you to lay down. In an ideal world, you will use five perfectly sized pieces of copper tape. That means each track of yellow on our template, where we will lay down the copper tape, has just one single piece being bent around corners.
Remember, to bend the piece of tape along each solid yellow line so there are no breaks. If you do have to cut your piece of tape midway you will need to cover that joint with conductive paint. Also, make a note of the gaps between the vertical pieces of tape from the shorter LED legs to the bottom horizontal line of tape that runs to the battery. If you close this gap you will have an RGB LED that is always on!
Your RGB LED has four legs, each of a different length. This template is set up for an RGB LED that has a common anode (a common top of the LED slide). Some RGB LEDs have a common cathode (a common bottom to the LED slide). If you happen to have the wrong one no worries, we can fix it with the flip of a battery later on.
The thing to note is the long leg, this is always the common leg whether you have a common anode or common cathode. The long leg is the most important leg.
Remember which leg is long! The long leg will shoot out to the left towards the battery in this template
I like to use copper tape to tape over the RGB LED legs along the line of tape that is already there. Taping along the current line of tape is important because if you tape across the leg instead you might connect other pieces of copper tape, which are the wires in our circuit. Doing so means your color piano won’t work properly.
You can also use scotch tape, or another type of plastic tape over the legs – I just like the additional contacts and feel it makes the circuit work better to use copper tape.
If your LED has a common anode then your battery should face up. That is, you should be able to see the writing on the battery like you do in the image. If you have a common cathode LED then you should flip your battery over so the writing is face down. If you don’t know what type you have just put it in face-up for now.
I find the best thing to use to clip CR2032 batteries in place is a small binder clip. You can also use tape, but the lack of pressure on both terminals of the battery might cause a flickering LED in the end.
Your keys should align nicely with your piano template as they are designed to be the same size. Gently place your keys on top of the piano as shown and press on key down to see if your LED lights up. If it does, congrats! Tape your keys down and play away. If it doesn’t, not to worry, there is always a lot of failure with circuits in general, even paper circuits. Check out our troubleshooting area below.
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