1. # Orrell's Quick Wall Paper Calculator

A trade show freebie which is almost a slide rule

2. # My proof of Descartes's theorem was just published

Where to find my latest publication

3. # A Cubic Spline for Animation

Developing a simple linear program for animating an LED string

4. # A Problem in Optimal Transport

We show why convex cost functions lead to certain types of solutions to optimal transport problems, using a simple example.

5. # An intuitive proof of the Descartes circle theorem

An original, intuitive proof of the Descartes circle theorem.

Reflecting on an old coding project, and what I would do differently now.

7. # Decoding a multiplexed LCD

Figuring out which segments are wired where on the TI-30Xa

8. # Lessons from the Xanthippe circuit board

Regrets and insights brought from the Xanthippe circuit board

A better way of generating Apollonian gaskets.

10. # Introducing Xanthippe

A formal introduction to my calculator validator

11. # A 3D-printed Planimeter For Use In Classrooms

A simple 3D-printable design for a planimeter, suitable for making a class set.

12. # Reading a Multiplexed LCD Signal

I want to read the signal going to the display of a TI-30Xa calculator. The display has 112 segments, multiplexed in a 4x28 configuration. How can we recover the displayed values from just those 32 pins?

13. # Reverse-Engineering a Matrix Keypad

The process of figuring out the layout of a keypad without looking at it directly.

14. # Reflections on wiring a calculator

Some thoughts on soldering, connectors, circuit repair, and test setups.

15. # Review: How to Do Nothing by Jenny Odell

I liked this book, it makes good points in interesting ways

16. # A Two Bit Analog-Digital Converter

A surprisingly simple circuit gives a reliable two bit analog-digital converter using only one integrated circuit chip.

17. # Measures of Bimodality

What are the most popular ways to measure the bimodality of a sample from a random variable?

18. # Pinball Science

an old game I enjoyed as a kid, which is now hard to install.