Author: John Elliot V

123 Articles

Schematic diagram of part of RAM

Making RAM For A TMS9900 Homebrew Computer

October 29, 2025 by 6 Comments

Over on YouTube [Usagi Electric] shows us how to make RAM for the TMS9900.

He starts by remarking that the TI-99/4A computer is an excellent place to start if you’re interested in getting into retro-computing. Particularly there are a lot of great resources online, including arcadeshopper.com and the AtariAge forums.

The CPU in the TI-99 is the TMS9900. As [Usagi Electric] explains in the video this CPU only has a few registers and most actual “registers” are actually locations in RAM. Because of this you can’t do much with a TMS9900 without RAM attached. So he sets about making some RAM for his homebrew TMS9900 board. He uses Mitsubishi M58725P 16 kilobit (2 kilobyte) static RAM integrated circuits; each has 11 address lines and 8 data lines, so by putting two side-by-side we get support for 16-bit words. Using six M58725Ps, in three pairs, we get 6 kilowords (12 kilobytes).

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A photo of the MMD-1 on the workbench.

Restoring The E&L MMD-1 Mini-Micro Designer Single-Board Computer From 1977

October 29, 2025 by 9 Comments

Over on YouTube [CuriousMarc] and [TubeTimeUS] team up for a multi-part series E&L MMD-1 Mini-Micro Designer Restoration.

The E&L MMD-1 is a microcomputer trainer and breadboard for the Intel 8080. It’s the first ever single-board computer. What’s more, they mention in the video that E&L actually invented the breadboard with the middle trench for the ICs which is so familiar to us today; their US patent 228,136 was issued in August 1973.

The MMD-1 trainer has support circuits providing control logic, clock, bus drivers, voltage regulator, memory decoder, memory, I/O decoder, keyboard encoder, three 8-bit ports, an octal keyboard, and other support interconnects. They discuss in the video the Intel 1702 which is widely accepted as the first commercially available EPROM, dating back to 1971.

Continue reading “Restoring The E&L MMD-1 Mini-Micro Designer Single-Board Computer From 1977” →

The winning entry, a photo of a fly on a grain of rice.

Nikon Small World Competition Announces 2025 Winners

October 28, 2025 by 3 Comments

They say that, sometimes, less is more. That would certainly apply to photomicrography, where you want to take pictures of tiny things. Nikon agrees, and they sponsor the Small World contest every year. The 2025 winners are a big — or not so big, maybe — deal.

This photomicrography competition dates back to 1975, so this is the 51st set of winners. First place went to [Zhang You] for his photograph of a rice weevil (sitophilus oryzae) on a grain of rice.

[You] is an entomologist from the Entomological Society of China. He says, “It pays to dive deep into entomology: understanding insects’ behaviors and mastering lighting, a standout work blends artistry with scientific rigor, capturing the very essence, energy, and spirit of these creatures.” We can’t argue with the results.

If you’re interested in Nikon and photography, you might also be interested in repairing a broken lens or a Nikon D3.

Record-Breaking Robots At Guinness World Records

October 26, 2025 by 12 Comments

If you ever wanted to win a bar bet about a world record, you probably know about the Guinness book for World Records. Did you know, though, that there are some robots in that book? Guinness pointed some out in a recent post.

Ever wonder about the longest table-tennis rally with a robot or the fastest robotic cube solver? No need to wonder anymore.

Our favorite was the fastest robot to solve a puzzle cube. This robot solved the Rubik’s Cube in 103 milliseconds! Don’t blink or you’ll miss it in the video embedded. Of course, the real kudos go to the team that created the robot: [Matthew Patrohay], [Junpei Ota], [Aden Hurd], and [Alex Berta].

Another favorite was the smallest humanoid robot. In order to win this record, the robot must be able to move its shoulders, elbows, knees, and hips just like a human. It also has to be able to walk on two feet. This tiny little guy meets the requirements and stands only 57.6 mm (2.26 in) tall! Created by [Tatsuhiko Mitsuya] in April 2024, this robot can be controlled via Bluetooth.

We’ve seen entries in this category before — check them out in Almost Breaking The World Record For The Tiniest Humanoid Robot, But Not Quite.

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A 2D simple regression analysis.

Making Math Less Stressful With A Python Super-Calculator

October 26, 2025 by 15 Comments

In a recent write-up, [David Delony] explains how he built a Wolfram Mathematica-like engine with Python.

Core to the system is SymPy for symbolic math support. [David] said being able to work with symbolic math easily has helped his understanding of calculus and linear algebra. For statistics support he includes NumPy, pandas, and SciPy. NumPy is useful for creating multidimensional arrays and supports basic descriptive statistics such as mean, median, and standard deviation; pandas is a library for operating on tabular data arranged into “DataFrames”, it can load data from spreadsheets (including Excel) and relational databases; and SciPy is a “grab bag” of operations designed for scientific computing, it includes some useful statistics operations, including common probability distributions, such as the binomial, normal, and Student’s t-distribution.

For regression analysis [David] includes statsmodels and Pingouin. If you’re not familiar with the term “regression analysis” it basically refers to the process of curve fitting. When your data is two-dimensional, with one dependent variable, the simple linear regression algorithm will generate a function that fits the data as y = mx + b, including the slope (m) and the y-intercept (b); this can be extrapolated to higher dimensional data and other types of regression.

If you have an interest in symbolic math you might enjoy learning about Mathematica And Wolfram On The Raspberry Pi.

A photo of the robot and the controller

A Simple $25 Robot Based On The ESP32

October 25, 2025 by 16 Comments

[Paul McCabe] wrote in to let us know about his $25 robot. This small wheeled robot is based on an ESP32 and made using cardboard and hot glue.

You drive the contraption using a Bluetooth game controller thanks to the Bluepad32 library, which boasts a long list of supported hardware. [Paul] provides a Bill of Materials (BoM), complete with current component pricing. We don’t know about you, but it struck us as funny that the microcontroller is less expensive than the battery! Ah, the times we live in. Also [Paul] assumes you already have an appropriate Bluetooth controller and doesn’t include that in the total cost.

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A frame from the two billion frames per second camera

Filming At The Speed Of Light, About One Foot Per Nanosecond

October 19, 2025 by 26 Comments

[Brian Haidet] published on his AlphaPhoenix channel a laser beam recorded at 2 billion frames per second. Well, sort of. The catch? It’s only a one pixel by one pixel video, but he repeats it over and over to build up the full rendering. It’s a fascinating experiment and a delightful result.

For this project [Brian] went back to the drawing board and rebuilt his entire apparatus from scratch. You see in December last year he had already made a video camera that ran at 1,000,000,000 fps. This time around, in order to hit 2,000,000,000 fps at significantly improved resolution, [Brian] updated the motors, the hardware, the oscilloscope, the signalling, the recording software, and the processing software. Basically, everything.

One of the coolest effects to come out of this new setup is how light appears to travel noticeably faster when coming towards the camera than when moving away from it. It’s an artifact of the setup: laser beams that reflect off of fog particles closer to the camera arrive sooner than ones that bounce back from further away. Or, put another way, it’s special relativity visualized in an experiment in [Brian]’s garage. Pretty cool.

If you found all this intriguing and would like to know more, there’s some bonus material that goes into much more depth.