The Stencil Light project has really been several projects in one.
The first thing I did was design a font to make stencils with to help teach my kids to write. The font includes stroke hints, and the curves are set up such that you can pick which to cut and which to mearly engrave when making a stencil. Honestly, they weren't a big hit with the kids. They played with them and had fun writing their names and such - but teaching them to write came later in a more traditional fashion.
As a result - I only completed the capital letters for the font. Here it is though, in case someone might find it useful (it's free for non-commercial use. For commercial use, contact me): BZStencil Font.
At first, I thought it'd be fun to have the stencils light up on a dry erasable metal board. So I did some experimentation with induction to light LEDs along the stencil edges. It kinda worked, but was going to take more time than I had to spend to make something viable with it. Fun stuff though.
For the light table, I've been through a *lot* of revisions. The first one I built was a craft-sized table, which they still use. It's Arduino controlled, and honestly a lot more complex than necessary. The top, which also acts as a diffuser, is a polypropylene cutting board. Big points for strength and durability, but because of the texturing it is awfully difficult to get crayon off of.
My current prototype in use is a 12"x12"x3" plywood box. The lit side is a translucent white acrylic sheet, while the opposing side is coated steel to allow for magnets. The lights are mounted on a Kydex sheet, with a clear acrylic sheet above them for protection and to allow the inside of the box to be used for stencil/pen storage when not in use.
Works great with dry erase pens and crayons directly, and the light is more than bright enough to allow tracing stuff with normal paper. The kids amuse themselves with it periodically, although they're still often forgetting to plug in the USB to charge it...
Using RGBW Neopixel LEDs has been a HUGE improvement when white lighting is desired. Highly recommend those. Initially I used the SMT LEDs and a custom board I routed, but have switched to the strips. The Trinket Lipoly backpack is another highlight, as for it's low price it does a great job of charging *and* the device can be used just fine while doing so.
More lights... I stuck an Arduino, an RGB LED strip, and an accelerometer into a gerbil ball. Kids liked it.
The Cat Climber was one of the earlier toys I made for the kids that I tried to set up for making a bunch of. It's a variant of the classic rope climbing toy - we have a bear that their great grandfather had made that I based it off of.
I designed them to be cut out by my CNC machine from 1/2" poplar. I chose poplar because it tends to be "fuzzy" rather than having sharp splinters, it's easy to acquire here, and easy to machine.
Cutting and assembling them is relatively simple after the first few, but sanding and finishing is quite the task!
Here's a few of them straight off the CNC machine, ready to be sanded, sanded more, assembled, oiled, and then sanded some more.
I've done some work towards making a slightly smaller version that could be laser-cut from plywood, but unless I ever own my own laser cutter it's probably not feasible for me to mass produce them at a reasonable cost.
The kids still enjoy them though. Can't go wrong with the classic designs!
Kids love buttons and switches and lights. So two of the early toys I built for them were essentially that - buttons, switches, and lights. The first one was the AND Box. Two switches, three lights. When the switches are on, the lights above them are on. If the left switch AND the right switch are both on, then a third central light is turned on. Boolean logic for toddlers.
It was enough of a success with the kids that I then built one with more of the basic Boolean operations - an entire Boolean Table.
They played with the Boolean Table for quite a while. The most fun for me though was actually swapping out the batteries - as it requires opening the bottom panel with screws and is quite an activity with two 2-3 year old kids.
So I'd get them to help me take the screws out, swap the battery, then put the panel back on and screw it down. And then the blinkies would work again, yay!