Sinclair ZX80 / ZX81 / Z88 Forums

If I wanted to make or repurpose a keyboard to use with a ZX81, is it safe to use the A8..15 Lines and the 5v connections on the edge connector? I know I'd need the pull-up resisters and the diodes, but would it be safe to do so? It would be nice to have an external keyboard which plugs into the back, but I prefer to have a working ZX81!

Cheers.

I used Wilf Rigter's schematic to create my own external keyboard controller. I'm sold out of the pcbs I made. It was my first electronics project, so anyone should be able to do it.

Yes, if using the edge-connector, as a minimum, you need a tri-state buffer (a chip where it's output pins can be switched to be open circuit) and some minimal control and address decoding to control the keyboard data going to the data bus.

Mark

Thanks for the replies. Looks like it would be a bit too complex for my abilities. Maybe I should just keep looking out for a Memotech keyboard or something similar on ebay. I imagine they are as rare as hens teeth.

Becky.

The German forum has designed a new controller and new keyboard with cherry keys with ZX81 symbols. It might be a product to buy soon.

Edit: Link to keyboard in German forum

Ooh. That looks nice!

Lardo Boffin wrote: ↑Sat Sep 08, 2018 5:44 pm Ooh. That looks nice!

Indeed!

Becky wrote: ↑Sat Sep 08, 2018 3:03 pm Thanks for the replies. Looks like it would be a bit too complex for my abilities. Maybe I should just keep looking out for a Memotech keyboard or something similar on ebay. I imagine they are as rare as hens teeth.

Becky.

It is possible to solder wires to the existing keyboard connector solder terminals on the underside of the Zeddy board. No need to disturb the existing keyboard or it's membrane.

That way, no electronic components are needed (apart from the switches of course ).
If you use coloured ribbon cable, you can fit it through the expansion port. Although it may get very tight for space if you have an expansion plugged in.

Mark

mrtinb wrote: ↑Sat Sep 08, 2018 3:22 pm The German forum has designed a new controller and new keyboard with cherry keys with ZX81 symbols. It might be a product to buy soon.

Edit: Link to keyboard in German forum

are they for sale anywhere ?

regards Andy

They will be most probably for sale in Mahlerts 2019. Are you and Sirmorris coming?