My kids are very curious about all of daddy's stuff and my littlest wants me to hold him next to the light switches in the hall so he can flip them up and down. I was inspired by the Instructables Childs Toy Light Switch Box to actually go out and buy some light switches. This project was fairly easy. Designing the board took the most time, because it took many sketches before I chose this design. Once I had all the parts, construction only took a few hours of work. I have a number of alternatives listed below which I may explore in future projects.
Step 1: Materials and Tools Needed
1x Acrylic (Plexiglass) sheet
1x Shadowbox Picture Frame (recommended) or electronics project box
1x 9V Battery
Spare wire (craft wire or single strands of telephone wire)
Glue or gluestick Hot Glue
Note: Different LEDs may have very different voltage drops. It is safe to assume 2V each, but I had some that were 3.3V.
Acrylic Drill Bit (best)
Standard Drill Bits (still good)
Hot Glue Gun
Soldering Iron w/ Solder
Step 2: Circuit Design
A mobile phone app called EveryCircuit is a great modeling program. When I got the app it was a little pricy, but I think they may have a limited version and in-app purchase for a full version. You can also use the app in a Chrome browser which is available after creating a free account on everycircuit.com . I made my design public so anyone can view and interact with it even if you don't have an account: http://everycircuit.com/circuit/5674053021204480.
I decided early on that I wanted more than just a simple one-switch-to-one-light interface. Rather than install relays (which might make cool clicking sounds) I decided that transistors were the next best thing to turn on additional lights when multiple switches were activated. Obviously my kids don't care either way. I also considered using a switch to activate the additional colors.
Step 3: Basic Materials
I selected a number of switches from Lowes that I liked. I wanted a good variety of pushbuttons switches and rocker switches. They also have acrylic (plexiglass) sheets pre-cut in standard sizes (mine is 8x10"). It hadn't dawned on me until my mother pointed out that a shadow box would be a great enclosure. Initially I wanted the board to be see-through so my kids could see the wires and components inside, but later decided that an instructional sheet would be better for my older kid.
Radio shack still exists!... sort of. My local Sprint/Radio Shack store has a number of project kits and drawers of individual components. They had almost everything I needed.
Step 4: Circuit Testing
This project was as much a learning experience for me as it is for my kids. I used an electronics kit (a 300-in-1 Electronic Project Lab) to test the transistors and confirm my wiring. A simple breadboard would also suffice, but would require me to wire all the switches in as well. I wanted to be sure I knew the correct pin-out for my transistors so 1) I didn't fry them, and 2) I wired them correctly. The circuit simulator isn't perfect and doesn't take into account the relative brightness of the LEDs. In retrospect, I would use more diffused LEDs and more resistance to tone down the brightness. Even after building, I still have some bleed-over on the transistor-switched LEDs.
Step 5: Board Design
I made a number of hand drawn sketches to determine which layout would make wiring as simple as possible (so I didn't confuse myself) and came up with two rainbow color-wheel circles. I designed the front face and component placement in tandem using GIMP (a free graphics editing program) and SketchUp (a 3D design program, formerly Google SketchUp), respectively.
GIMP allowed me to make smooth lines using the "paths" tool, which I could later use to create a layer mask and cut out a rainbow graphic I found at http://www.psdgraphics.com/backgrounds/blurry-rainbow-colors-design/.
SketchUp is a powerful (and free) software program that allowed me to build individual components and move them around the board without cutting a single thing. This really deserves a tutorial all its own because there are so many features I used. My SketchUp model (version 2016) is attached.
For simplicity, I'll list the capabilities I used and let you research them on your own:
- Draw "guides" at measured distances. Draw simple shapes starting and ending at very specific points.
- Draw polygons with specific number of sides (triangles and hexagons). So they don't have do be drawn free-hand or measure angles.
- Measurement snapping (can use a mix of metric and imperial scales).
- Make "groups" from a selection of lines and faces. When drawing new components on top of other components, you need a way to tell SketchUp that this is a new component to be moved around the board after it is drawn. Literally, drawing separate components.
- Copy and move groups. Build an item anywhere and move it around afterward. Also, each piece doesn't need to be built individually. I had two circles which are identical but rotated 30 degrees. It was easiest to build one completely, then select all components from one circle and make that into a group which could be copied, moved, and rotated as a single unit.
- Rotate the camera view from the front to the back to ensure the switches are far enough apart and to work both sides of the board.
- Create "views". Quickly jump from the front to the back and have specific layers activated with each view. Groups can be assigned to specific layers, even specific lines within a group can be assigned independently to a given layer.
- Labels for everything. Once a group is created, it can be named. Then use the label tool to show that name in a call-out.
- Create multiple layers that can be turned on and off. Aids in the design process because specific components can be assigned to a given layer and turned off (hidden) to measure the holes they leave in the sheet layer. When finished, dimensions can be hidden to take a snap of the completed product.
- Add actual dimensions to everything, which can be printed.
- Export 2D image from SketchUp and import into GIMP.
- Apply an image (from GIMP), as a "texture" to the final board. This is an amazing feature to marry the work done in both programs with only a few clicks.
Step 6: Printing and Cutting
SketchUp comes with another program called "LayOut" which allowed me to take live snaps of the SketchUp model and display them (to scale) on a sheet of paper (I used a 1:1 scale). Activation of specific layers requires use of the "create views" feature I mentioned earlier. This program is key because it allowed me to print both the front-side image and the dimensions on each side of the same sheet of paper. When held to the light, I had only a 1mm margin of error.
I taped a copy of the two-sided sheet to the back of my plexiglass sheet, one side was the finished graphic and dimensions for the other. I used drill bits for the circular components and a utility knife for the square ones. Punching holes around the square components made use of the utility knife much easier. Obviously, having an actual acrylic bit (as opposed to metal bits) would have saved me from all the cracks. You definitely want a good tight fit for at least the LEDs so the kids can't push them out. The other components had nuts that screw down to hold them in place.
Step 7: Install Components
Once all the design aspects were out of the way, construction went very quickly. I glued (with gluestick) and taped (the edges) of a fresh, high-quality copy to the back of the plexiglass. I first installed the LEDs (hot gluing them in) and soldered each negative (-) terminal to a ground wire that ran all the way around the board. I then soldered a resistor to a battery connector and tested each LED to ensure it was wired in with a good connection.
Solder all switches to each other, this will become the positive lead I wired to one pole (per circle) of the single-pole double-throw (SPDT) switch at the end of the dashed lines. The center LED's resistor is also wired direct to the SPDT.
Next, solder resistors to each LED as close to the bulb as possible. Use the excess lead to make the connection direct to the switch. (Note: I was figuring out the best placement for all the components and testing them direct to the battery when I touched battery to an LED lead. That's the reason my blue doesn't show in the pictures on the right circle.)
Solder resistors to the transistor-controlled LEDs as close as possible. Soldier the emitter of the transistor as close as possible to the resistor. Then solder the controlling resistor to the transistor's base (the middle lead in my case) and connect the free lead direct to the next switch. And finally, solder a wire between the transistor's collector and the previous switch. (Note: This method took a couple to figure out, but helped the rest go in fast.)
Last step, solder the controlling terminal of the SPDT to the battery.
Note: I intended to create the timer circuit (center of my schematic) and wire it in to automatically shut off like every kid's toy I've ever seen, but was too excited to have my kids play with it. So I wired the red pushbutton (bottom right corner) between the SPDT and the battery so my kids can't leave it on all the time. They still love it and quickly learned to hold the red button to keep it running.
Step 8: Conclusions
- My kids love the board, switches, and lights despite my criticisms of my work. It isn't yet inside of a shadow box, but the voltage isn't high enough to cause concern.
- Some of the LEDs are super bright, especially the blue! If I made this again, I would spend more time getting the right resistor to tone down the brightness and fix the transistor bleed-over. I may wire in a 2x AA battery holder to see if that works better.
- A note on the transistor bleed over, I initially had a 1K resistor there, but increased it to 39K based on recalculation of the transistor cut-off voltage and availability at the store.
- A project like this definitely needs to have an auto cut-off method. I think the pushbutton is a great one because it forces my kids to figure it out and adjust (and is otherwise work-free).
- Extra pushbutton. I have an extra pushbutton that activates with a lot more pressure than I anticipated so I plan to wire that to activate both circles of lights for my older kid.
- For those with older kids, having the wiring diagram printed on the back of the page will make it easier for them to follow along and put components in the proper place.