Making Logic With Inductors


We’ve seen NAND and NOR logic gates – the building blocks of everything digital – made out of everything from marbles to Minecraft redstone. [kos] has outdone himself this time with a logic circuit we’ve never seen before. It’s based on magnets and induction, making a NOR gate out of nothing but a ferrite core, some wire, and a diode.

The theory of operations for this magnetic NOR gate goes as follows: If two of the input windings around the core have current passing in different directions, the fields cancel out. This could either be done by positive or negative voltages, or by simply changing the phase of the winding. To keep things simple, [kos] chose the latter. The truth table for a simple two-input, one-output gate gets pretty complicated (or exceedingly cool if you’d like to build a trinary computer), so to get absolute values of 1 and 0, a separate ‘clock’ winding was also added to the core.

One thing to note about [kos]‘ gate is its innovation on techniques described in the relevant literature. Previously, these kinds of magnetic gates were built with square ferrites, while this version can work with any magnetic core.

While this isn’t a very practical approach towards building anything more complex than a memory cell, it is an exercise of what could have been in an alternate universe where tube technology and the transistor just didn’t happen.

Arduino magnetic core memory shield


Magnetic core memory turns 60 years old today, and as a tribute [Ben North and Oliver Nash] have created a 32-bit magnetic core memory board for the Arduino.

Magnetic core memory was used from the 1950s through the 1970s, and provided a non-volatile means for storing data, as each magnetic core retained its orientation, even when the power was cut. While it sounds a lot like a modern hard drive, these devices were used in the same fashion as RAM is utilized today.

While the pair used surplus ferrite cores manufactured just before magnetic memory stopped being produced, they did allow themselves to use some modern components. Items such as transistors and logic gates were not available to the first magnetic core memory manufacturers, but the use of these items helped them complete the project in a reasonable amount of time.

Their final result is a magnetic memory board which can be used by any USB-enabled device and is reliable enough to withstand billions of read/write transactions.