Category Archives: logic

Relay Computing

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Recently, [Manuel] did a post on making logic gates out of anything. He mentioned a site about relay logic. While it is true that you can build logic gates using switch logic (that is, two switches in series are an AND gate and two in parallel are an OR gate), it isn’t the only way. If you are wiring a large circuit, there’s some benefit to having regular modules. A lot of computers based on discrete switching elements worked this way: you had a PCB that contained some number of a basic gate (say, a two input NAND gate) and …read more

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Yes, You Can Reverse Engineer this 74181

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[Ken Shirriff] is the gift that keeps on giving this new year. His latest is a reverse engineering of the 74181 Algorithmic Logic Unit (ALU). The great news is that the die image and complexity are both optimized for you to succeed at doing your own reverse engineering.

We have most recently seen [Ken] at work explaining his decapping and reverse engineering process at the Hackaday SuperCon followed soon after by his work on the 8008. That chip is crazy with complexity and a die-ogling noob (like several of us on the Hackaday crew) stands no chance of doing more …read more

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Make Logic Gates out of (Almost) Anything

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Logic gates are the bricks and mortar of digital electronics, implementing a logical operation on one or more binary inputs to produce a single output. These operations are what make all computations possible in every device you own, whether it is your cell phone, computer, gaming console etc.  There are myriad ways of implementing logic gates; mechanically, electronically, virtually (think Minecraft), etc. Let’s take a look at what it takes to create some fun, out-of-the-ordinary gate implementations.

How they work

As an example, let’s consider the AND gate (the others are OR, NOT, NAND, NOR, XOR and XNOR). Electronic gates …read more

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Taking It To Another Level: Making 3.3V Speak with 5V

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If your introduction to digital electronics came more years ago than you’d care to mention, the chances are you did so with 5V TTL logic. Above 2V but usually pretty close to 5V is a logic 1, below 0.8V is a logic 0. If you were a keen reader of electronic text books you might have read about different voltage levels tolerated by 4000 series CMOS gates, but the chances are even with them you’d have still used the familiar 5 volts.

This happy state of never encountering anything but 5V logic as a hobbyist has not persisted. In recent …read more

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Two Pins for the Price of One

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One of the most common problems in the world of microcontrollers is running out of resources. Sometimes it’s memory, where the code must be pared down to fit into the flash on the microcontroller. Other times, as [Fabien] found out when he ran out of pins, the limitations are entirely physical. Not one to give up, he managed to solve the problem by using one pin for two tasks. (Google Translate from French)
During a recent project, [Fabien] realized he had forgotten to add a piezo buzzer to his project. All of the other pins were in use, though, so

…read more

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Fallout 4 Gets Logic Gates, Is Functionally Complete

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Fallout 4, the latest tale of post-apocalyptic tale of wasteland wanderers, got its latest DLC yesterday. This add-on, Contraptions Workshop, adds new objects and parts to Fallout 4‘s settlement-building workshop mechanic. This add-on brings more building pieces, elevators, and most importantly logic gates to Commonwealth settlements.

The Fallout logic gates are used in conjunction with electric generators, lights, and automated sentries used to build settlements. Although a simple NAND would do, there are several types of logic gates including AND, OR, XOR, NOT, NAND, NOR, and XNOR.

The in-game explanation for these gates is very, very weird. AND, …read more

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