In March 2012, I discovered the Codea app, allowing coding on an iPad, and the Lua programming language, its foundation. That was the unlikely seed for discovering the functional programming language Haskell in late 2013: a Codea discussion mentioned Project Euler and Haskell solutions to its problems. In particular, a one-line solution for Problem 9: […]
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Rebuilding a Mac mini
In January 2012, I wanted to learn Apple’s Objective-C programming language, so I bought a basic Mac mini and a book. The Mac was a ‘mid 2011’ model, configured with a 2.3 GHz Intel Core i5 processor, 2 GB of RAM and a 500 GB hard drive. The book was Programming in Objective-C by Stephen […]
Experiments with IIS and PHP
After many years of hand-tooling HTML, I bit the bullet and installed WordPress. That has sparked an interest in PHP, the server-side scripting language. I needed a local copy to experiment with. Turning on IIS First, I needed web server software. The operating system on my PC is currently 64-bit Windows 10 and Windows comes […]
Countdown Mk 2
Summary A three-digit initial state, determined by three 4-position dual inline (DIL) switches, is set by pressing Switch 1 (SW1). Pressing Switch 2 (SW2) starts a count down to zero. When zero is reached, the light emitting diode (LED) lights up. The progress of the count is shown by a three-digit seven-segment liquid crystal display (LCD). This improves […]
POR
Summary The initial state of an SR (set-reset) latch is, in principle, indeterminate. The circuit is a SR (set-reset) latch with a power-on reset (POR), so that the initial state after power-on is determined. Circuit Schematic Transistor T3 is off while capacitor C1 charges through resistor R5. Consequently, the voltage at the collector of T1_L […]
Countdown Mk 1
Summary A three-digit initial state, determined by three 4-position dual inline (DIL) switches, is set by pressing Switch 1 (SW1). Pressing Switch 2 (SW2) starts a count down to zero. When zero is reached, the light emitting diode (LED) lights up. The progress of the count is shown by a three-digit seven-segment liquid crystal display (LCD). […]
Adder
Summary The circuit adds two four-bit numbers. The input is by means of a single eight-position DIP (dual in-line package) switch. The output is displayed using a five-bar LED (light-emitting diode) bar graph. Circuit The least significant digits are highest in the image. Switches 4 to 1 are one input and switches 8 to 5 are the other. […]
Tone
Summary The circuit drives a speaker to generate a tone. The frequency of the tone can be varied by adjusting a trimmer. Circuit Schematic Stripboard The stripboard size is 9 tracks of 25 holes.
Clock
Summary The circuit switches between lighting one of two light emitting diodes (LED). The frequency of the switching can be varied by adjusting a trimmer. Circuit Schematic The circuit was originally intended to be powered by four AA batteries, each with a nominal voltage of 1.5 V (6 V in total). The batteries are relatively […]
SR latch
Summary The circuit is a SR (set-reset) latch. The input is by means of a two tactile switches (set and reset). The output is displayed using two LEDs (red and yellow for Q and not Q). Circuit Originally, the power connector was a two-position screw terminal (as in the images above). This was replaced with […]