# Trying to make a RGB LED 3-button wand--complete noob

#### mirthfulArtist

Joined Nov 18, 2017
3
Hello!
I want to start by saying that I have no experience/education regarding circuitry beyond gradeschool basics. I'm an illustration student making a very basic prototype for a Toy Design class.

I want to make a magic wand toy that can light up in different colours. I was hoping to use a single RGB LED, but three separate coloured LEDs could probably work too. All that matters is that colours can be lit individually OR mixed. Basically I want each colour to be controlled by a button so that you can have any combination of them on at once to produce the colour you want.

I'm a little lost when it comes to resistors and power supply. Do I need seperate resistors for each colour anode of the RGB LED? What kinds do I need? Can these all be hooked up to a couple AAA batteries? I've seen tutorials online for Harry Potter wands, but these all use just 1 plain LED, no resistors at all, and are frightfully vague in their supply lists.

Thank you for helping out a true noob. I don't have a soldering gun or any other machinery since I'm away from home, but I think I can rent a few simple tools from my school if I need to. I doubt a breadboard would work given the shape of the toy I'm making.

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#### dl324

Joined Mar 30, 2015
13,532
Welcome to AAC!

Since you didn't specify a specific RGB LED, I pulled a random datasheet from the internet. For the first one I found, 3V would be marginal:

Three on/off switches would give you a limited number of colors.

If you want to be able to set the wand to any arbitrary color, that will require varying the current in each LED, or controlling the amount of time any color is on/off (via pulse width modulation - PWM). That can't be done with three switches unless you include a microcontroller.

#### mirthfulArtist

Joined Nov 18, 2017
3
Welcome to AAC!

Since you didn't specify a specific RGB LED, I pulled a random datasheet from the internet. For the first one I found, 3V would be marginal:
View attachment 139612

Three on/off switches would give you a limited number of colors.

If you want to be able to set the wand to any arbitrary color, that will require varying the current in each LED, or controlling the amount of time any color is on/off (via pulse width modulation - PWM). That can't be done with three switches unless you include a microcontroller.
It will probably be a standard-sized, 5mm RGB LED, if that helps. Common cathode or common anode, depending on what this crowd thinks will work better for this project...The store I'm going to has all sorts, so I'm not limited in that sense.
I am fine with a limited number of colours for now--this is my first stage prototype, and basically we only have to be able to "fake" the play experience we're going for. (In fact, my actual concept if a lot more complicated and involves AR communication, colour sensors, and other such shenanigans...but these are all beyond my ability and resources, so for now, Three buttons for three colours is fine.)
What I need help with is just the type of resistors and power supply to hook it up to, if resistors are needed at all.

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#### mirthfulArtist

Joined Nov 18, 2017
3

#### dl324

Joined Mar 30, 2015
13,532
My browser refused to open those URLs.

Since the green and blue LEDs are likely to have a forward voltage around 3.5V, you should use 3 AAA batteries.

To calculate resistor sizes:
$$\small R = \frac{V_{BAT}-V_{LED}}{I_{LED}}$$

With three switches, you can get R, G, B, R+G, R+B, G+B, R+G+B, and off.