About the sequencer

Created by Masashi Satoh | 11/20/2025

Introduction

Here is a detailed introduction to the sequencer used for automatic calculations with the adder.

This simple sequencer dramatically enhances the learning experience of computers. With basic knowledge of electronic circuits and some crafting skills, you can build it yourself—so please give it a try.

Circuit diagram

The PDF of the circuit diagram is available below. This is the prototype version created as a test build, featuring a design that places slightly excessive strain on the shift register’s output.

While an improved design exists, I have chosen to release the prototype version that is confirmed to function reliably, as the new design has not yet been physically constructed and tested.

This circuit has operated without issues for over ten years, so I believe building it as is should pose no problems.

Production Notes

• The schematic shows resistors connected to the LEDs, but I used only built-in resistor type LEDs rated for 5V. Specifically, the OptSupply OSR6LU5B64A-5V. If built-in resistor type LEDs are unavailable, please insert resistors as shown in the schematic.
• Select a small relay capable of converting the shift register’s output to a 12V voltage that drives the adder’s relay. Choose one with specifications that can be driven by the output of the 74HC series. I used OMRON’s G5V-1 DC5. If a relay operating with a small current is difficult to obtain, drive it through a transistor buffer circuit.
• The universal board used to construct the circuit measures 15.5mm x 11.5mm. Considering its handling, this can be considered a suitable size.
• The completed sequencer is used as-is, without being housed in a case or similar enclosure. I believe this approach best preserves the spirit of a class exploring the inner workings of computers.
• As described on another page, if diodes for surge voltage suppression are not installed on all relays of the connected adder, the sequencer will malfunction.
• The completed sequencer is used as-is, without being housed in a case or similar enclosure. I believe this approach best preserves the spirit of exploring the inner workings of a computer. For preliminary preparations and to facilitate the spread of this lesson, I also consider it necessary to create printed circuit boards.
• I believe an 8 x 3 LED pixel count is optimal for visibility and operability. I understand that educators with a technical background might desire more capabilities. However, education requires constantly considering what is essential and exercising restraint.