Calculator Keypads

As described in my 2023 goals post, my plan for the year was to finish enough projects to give a presentation at the 2023 Hewlett-Packard Handheld Conference (HHC). Even though I didn't finish everything on my list, there were still enough interesting things to give a presentation on including my Blinky Robot and 6507 Calculator Forth Virtual Machine. The largest part of the presentation was about building calculator keypads.

While building a circuit board or writing the firmware for a calculator are achievable goals for a hobbyist or amateur, building a keypad tends to be much more challenging. The keys themselves can be made on a 3D printer, but getting good quality labels on the keys is very difficult. Since none of my calculator projects so far have had really good keypads, I decided to try every method available for making keys to compare the results.

3D Model
The 3D model for the test consists of eight rows of five keys each designed in OpenSCAD for my still unfinished 6507 Graphing Calculator. OpenSCAD has been my go-to program for modeling since I started with 3D printing a few years ago. The biggest advantage of this program is that the entire model is specified by a script so nothing needs to be manipulated or placed by hand. This works well for people like me who don't have a lot of artistic talent but feel comfortable with programming. It's cheap and relatively quick to print out a set of these keys on my Ender 3.

Kitty Salon

For Christmas this year, my girlfriend and I made a talking toy cat for her nephew. It was a fun opportunity to build something together and practice some fabrication skills that are useful for calculator projects.

The idea for this project came from her nephew pretending to be a cat and calling himself "Kitty Salon." The toy version of Kitty Salon has five recorded messages saying things like "Meow! Meow!" and "Rise and shine!" A button on the bottom plays one of the messages every time it's pressed, cycling through all five. Two LEDs for eyes glow to show that the cat is on and fade on and off while the cat is talking.

Body

The first step to building the cat was sculpting a model out of clay. The innermost part of the model is a small box made out of foamcore which is large enough to hold all the electronics. The first try at making the cat out of clay from the craft store failed. The box the clay came in said that it dries when exposed to water. In our case, the model cracked in several places after drying and the feet fell off. The second try used Sculpey which doesn't require water to set and has the added benefit of working well with silicone rubber molds. You can see in the picture above that the back end of the cat is a little square and fat since the Sculpey is molded around the box for the electronics.