My 13 months old son is a busy, busy boy who loves lights (just like his daddy). To keep him entertained, I recently started making various toys for him - busy board, light switch board (base on this one), etc.

This specific project serves two purposes. First, I wanted something small and simple that will keep him entertained during plane and car rides. Second, I used it as prototype before making something more sophisticated (with a micro-controller, rechargeable battery, and all the other goodies).

The design itself is simple - there's the cube structure itself (made of 6 pieces of plywood), and the on/off switch module. The later includes the switch, and two battery holders that are glued to it. This whole unit slides into the cube, and then secured with four small M2 screws.

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(I apologize for the quality of the photos in this Instructable. I was in a hurry to get this done, and all I had was my phone and very bad ceiling lights in my office)

Step 1: What You'll Need

1/8" (3mm) plywood. We will use this for the cute
Blue Light 4 Pin DPST On/off Snap Rocker Switch (or any color you like). I found mine at the MIT flea market, but you can find them anywhere
5mm white LED. You will use this one to replace the light in the switch
4 x 2M screws, 6mm - 10mm long.
2 Coin cell battery holders. Try to find something small with a low profile. I used these
Epoxy glue or hot glue. I used epoxy
Some wood glue
Some wires. To connect the battery holders to the switch

Step 2: Cube Cutting and Assembly

This part is easy. Use one of the attached files to cut the cube parts out of the 1/8" plywood. You'll notice that you have 7 pieces - 6 for the cube structure, and one additional part for holding the switch. The 7th part has a rectangular hole and 4 tiny screw holes. Put this part aside, and focus on the other six.

Assemble the 6 pieces to compose the cube and make sure they fit well. Apply small amount of wood glue to the pieces, and if you have small clamps, use them to hold the cube together.

Step 3: Replacing the LED in the Switch

Warning!!! you are going to modify a switch that is supposed to work with high voltage, and place a low voltage LED inside. Make sure you mark it well so no one tries to connect it to high voltage in the future.

The switch we use here is meant to be used with mains (110 - 240v, depending on what you got). Since we want to use this with a small 3V coin cell, we'll have to replace the tiny bulb it has inside with a regular low voltage LED.

First, use a small screwdriver to lift the black casing and pull out the switch itself (first photo). The second photo shows the parts inside the switch - there are two metal parts that control the movement and whether the circuit is closed or not, the blue switch, a white part that contains the bulb, and two small springs that connect the bulb with the terminals. Take a photo of what it looks like so you know how to put it back together.

Next, use the screwdriver to pop out the white part (third photo). Inside, you will see a tiny bulb and a resistor. Remove both, and replace with your LED. You will probably need to cut/sand down the LED and make it shorter, so it fits inside the blue cover. Note that the LED legs need to touch the springs. In my case, there was this funny grease on the springs. I believe it is meant to hold the springs in place during assembly, but it also affects the conductivity. If that's the case, make sure to clean it up a little.

Now, put everything back together and make sure it's working: use a coin cell battery and make sure that the LED is indeed working and check the orientation of the on/off switch. Also, mark which connectors are used for powering the LED so you know where to connect the battery compartments.

Step 4: On/Off Switch Module

First, put the switch into the rectangular cut in the plywood piece. Depending on the exact size of your switch, it should snap in with some force.

Next, solder wires to the battery holders and make sure you got the polarity right.

Glue the battery holders to the (long) sides of the switch. I used epoxy so that I don't add much to the width of the unit. If it's too wide, it might not fit in the cube. Depending on the battery holder you got, maybe sure you leave enough room between the battery holder and the plywood so that the battery can fit there.

Finally, we connect the battery in parallel to terminals of the switch. This means that the "+" on both battery holders go to the same terminal, and the "-" of the battery holders go to the same terminal (see image). Again, make sure you connect everything to the right place before and that the LED turns on and off correctly.

Step 5: Putting It Together

Now just slide the switch module into the cube, and secure it using the 4 screws. Use sand paper (200 - 320) to round all corners and edges of the cube so there are no sharp corners or edges.

That's all!