CompuLab - a DEC H500 Inspired Logic Trainer

CompuLab is a simple logic trainer I designed as a labour of love for one of those "ancient" pieces of electronics developed in the bronze age: the DEC H500.

The original DEC H500 is rare, very sought after and expensive nowadays, so here it is a cheap alternative for everyone.

Let's do it!

Compulab is a reinterpretation of the DEC H500 logic trainer from the late 60's.

As said, this hardware is rare and expensive, but there's another part of the equation: the documentation DEC realized for that. Thanks to today's technology, we have access to both the workbook and teacher's guide DEC specifically realized and lot of engineers learned digital logic with...

... all for free!

What is missing is something (who said "hardware plase!") to put those instructions and excercises in practice: here is where Compulab comes to our aid.

To keep the project easy to make (and cheap) I designed it as a small module with a decent amount of logic operators.

A single CompuLab module has just less then half of the logic operators of a full H500, but you can use more than one module to increase the number of operators.

I placed two DC barrel for the pourpouse of parallel power supplying.

Follows a complete list of components:

Logic Operators
2x 74HCT73

1x 74HCT02

1x 74HCT08

1x 74HCT10

1x 74HCT20

1x 74HCT00

Input Section

4x switch SPDT/1P2T

4x LED 3mm

4x resistors, 2Kohm

154x pinheaders, male (yes: one hundred and fifty four :) )

Clock Generator

1x poly cap, 10nF

1x poly cap, 1000nF

1x trimpot, 1Mohm

1x NE555

1x resistor, 47Kohm

Others

2x DC barrel 5.5x2.1 mm

... and a whole lot of 20 cm Dupont cables, female-female, for connecting modules and inputs.

Clock source components are a function of the clock frequencies you are interested in. I used 1uF and 10nF poly caps, a 1M ohm trimmer and a resistance of 47K ohm to achieve a minimum clock frequency of 1 pulse/s.

To keep everything compact and clean, I had to use logic operators in surface mount device (SMD) packages. Nothing too difficult to solder with the help of some solder flux (any Rosin Flux Pen will work good), don't worry!

Please, keep in mind that there's not a circuit against power polarity invertion, nor a voltage regulator: feed Compulab with regulated 5V such those used for USB deviced.

You can have your CompuLab printed circuit boards manufactured at PCBWay - PCB Prototype the Easy Way at this link:

https://www.pcbway.com/project/shareproject/CompuL...

Select a nice color, assemble a couple of those and have fun with excersises from the Workbook (see next step)!

You can get DEC H500 workbook and teachers guide almost everywhere on the net. I want to suggest you to get them at this great instructable here:

https://www.instructables.com/DEC-H-500-Computer-L...

You will find a lot of interesting informations

Enjoy the reading!