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Please note: We do not currently ship to the US.


UK Delivery via Royal Mail First Class (1 working day)

EU Delivery via Royal Mail International Standard (3-5 working days)


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The S1-AU Mk1 is a beautifully crafted DIY hardware kit designed with 7400 series logic chips. It enables you to build a simple 4-bit arithmetic unit and manually perform simple binary operations. It has been designed for pragmatic computing enthusiasts, hobbyists and makers.

Using 74HC173 registers for temporary data storage, a 74HC283 full adder for binary calculations, and a 74HC85 comparator for logical comparisons, the assembled board enables an operator to perform 4-bit addition, subtraction, accumulation and comparison.

Input into the unit is performed manually through an array of push button switches and binary operations can be traced through a series of on-board ultra bright LEDs.

The S1-AU Mk1 is powered via a USB mini cable, however it is not programmable - it requires manual operation through on-board switches. The USB cable is only used to deliver power to the unit, so you don't need to rely on batteries.

The kit contains all the through-hole components you’ll need to build your own 4-bit arithmetic unit and includes:

- S1-AU Mk1 Mainboard PCB

- Backplate PCB (with screws and nuts for mounting)

- Electronic Components Kit

- USB Mini Cable (for power only)

- Operator's Technical Manual (downloadable .pdf - English language only)

The kit is supplied with our 'Operator's Technical Manual' (as a downloadable .pdf - English language only) which describes in detail what the arithmetic unit is and how ALUs are used more generally in computational architecture. The manual also explains how to fully construct and operate the S1-AU Mk1 and gives a primer on binary operations (addition, subtraction & twos complement) for those who may not be familiar with binary arithmetic. Our mainboard PCB has been carefully crafted to complement the manual and aid construction.


The S1-AU Mk1 is recommended for ages 16+. It is not a toy. Some soldering experience is required to construct the kit.

Photos and videos show our pre-production S1-AU Mk1 board. Our released kit may be subject to minor design and layout changes.