The Maplin I/O Board

For the discussion of all hardware related topics.
Post Reply
Serenarian
Posts: 35
Joined: Thu Oct 25, 2012 1:28 pm

The Maplin I/O Board

Post by Serenarian »

I was just browsing through my photos on old SD cards when I rediscovered these.
I built up the Maplin I/O card and used it to control a model railway, and a radio controlled tank
(way back in the 1980s)
The original card addressing conficted with the disk controller, so I made the mods on the underside.
Quite a handy little board - that might be of interest to others.
Attachments
PICT0176.JPG
PICT0176.JPG (1.14 MiB) Viewed 50130 times
PICT0175.JPG
PICT0175.JPG (984.93 KiB) Viewed 50130 times
PICT0172.JPG
PICT0172.JPG (1.78 MiB) Viewed 50130 times
Serenarian
Posts: 35
Joined: Thu Oct 25, 2012 1:28 pm

Re: The Maplin I/O Board

Post by Serenarian »

As this created some interesting comments on the CoCoNation Podcast (10/05/2025) - Well spotted Curtis.
I thought I would explain about Maplin Elctronics and provide a link to the September 1983 magazine article.

in the States they had Radio Shack and Heathkit, in the UK we had Maplin Electronics which was started as a mail order business in 1972 by two electronics enthusiasts who were frustrated trying to obtain components for their projects. They ran it from their attic room, producing a catalog of common electronic components. The business quickly expanded beyond simple mail order, and by 1982 had high street stores and a turnover of over £3m. It was well placed to make the most of the computer boom and published a bi-monthly magazine of projects for the hobbyist. But sadly, over extended, with high interest loans Maplin closed its last retail store in 2018 and has subsequently relaunched itself as a pale shadow of the original.

To give you an idea of the scope, its quarterly colour retail catalog, of which I have the April 2000 issue, ran to 1184 pages.
Follow this link to find past catalogs and Maplin Magazines:

https://www.worldradiohistory.com/Mapli ... ronics.htm

If you pull up the September 1983 magazine you will find the complete details of the Dragon I/O boards that I built. I’m not the designer or the author.
For £13.95 which was about $17, you got the silk-screened double sided board and all the components. That included everything including the PIA and the 2 relays. All you had to do assemble and solder it (oops, sorry Curtis!).
I built two – one for the railway set, and a second as part of some lectures to demonstrate interfacing at the NorthWest TRS-80 User Group. The railway would have been too big to transport, so I opened up an RC transmitter that drove a RadioShack RC Sherman Tank (thanks to Kevin Harper our friendly Tandy RS shop manager), and used the I/O board to do what the joysticks did. The software side was all in Dragon BASIC – just like the DRAW commands. Somewhere I may still have the code. One issue was that this board’s addressing was designed for the Dragon32 and used &HC000 – &HC003 as the 6821 PIA addresses. I made some changes on the underside to use &HFFxx addresses.

As for the risk of “blowing things up” as Rick mentioned, the 2 relays have transistor drivers and are rated as 1amp and up to 100volts DC. The Vero board that I made added 4 more. There are two opto-couplers too that can only handle low current. It is not rated to switch mains voltages and currents. It proved safe and reliable for my demos and the Tank made more of an impression than the blinking lights interface projects or on-screen turtle graphics.

Peter Mooney
Post Reply