The Sinclair QL Forum

Posted: **Mon Sep 20, 2021 3:17 pm**

Derek_Stewart wrote:HI,

I used a 1N4148 Signal Diode, the idea is to join to signals to a switch but not short them out.

The diode stops reverse signal flow.

Would join 2 connections to one switch without shorting out the source.

I tried some ASCII art, but the Forum software seems to strip out white spaces.

Code: Select all

  | | |
   - -

Use a code block!

Posted: **Thu Oct 28, 2021 6:16 pm**

Derek_Stewart wrote:HI,

I used a 1N4148 Signal Diode, the idea is to join to signals to a switch but not short them out.

The diode stops reverse signal flow.

Would join 2 connections to one switch without shorting out the source.

I tried some ASCII art, but the Forum software seems to strip out white spaces.

Can you please draw a raugh schematics and post it here?

Posted: **Thu Oct 28, 2021 9:59 pm**

Nasta said

Nasta wrote:No. All keys must be wired between one row and one column line.

The reason being that you don't have one signal when both keys are being looked at you have two input signals and two read lines. You need to operate two independent switches at once. Could it be fudged with diodes & passive components I don't know.

signal A -----o__o------ read A

signal B -----o__o------ read B

Off the top of my head perhaps using a switch that was attached to the gates of two FETS might achieve it.

----signal A -----d__s------ read A
Gate 1 >>>>>>>> |
----signal B -----d__s------ read B
Gate 2 >>>>>>>> |
5V--singleKEY-----|

Well that was fun trying to get things in the right place.

Posted: **Thu Oct 28, 2021 10:19 pm**

Derek_Stewart wrote:I tried some ASCII art, but the Forum software seems to strip out white spaces.

ASCII art will work in forum if you put it within the Code block tag. You'll have to create it outside fo the forum because the built-in editor uses kerned font but the Code tag will use monospace font when you preview or submit.

Code: Select all

__________________           __
\_________________|)____.---'--`---.____
              ||    \----.________.----/
              ||     / /    `--'
            __||____/ /_
           |___         \
               `--------'

Posted: **Thu Oct 28, 2021 11:12 pm**

bwinkel67 wrote:ASCII art will work in forum if you put it within the Code block tag

Oh! that's what XorA meant with the dots & dashes.

I thought it was morse code.

Thanks.

Posted: **Thu Oct 28, 2021 11:29 pm**

Hi,

The ASCII art is very nice, I am not an artist, so struggle a litgle.

With regards to the keyboard controlling 2 lines like CTRL and C to give the change of job function, 25 years ago I think I tried guiding the lines with signal diodes, but it did not really work, but I used 2 Transistors with the base of each transistor base attached to the keyboard switch and the common and emitter attached to the keyboard line.

Once switch is pressed a high signal is passed to each transistor which switches on each keyboard line.

I will draw up what I mean.

Posted: **Fri Oct 29, 2021 9:26 am**

Ruptor wrote:
bwinkel67 wrote:ASCII art will work in forum if you put it within the Code block tag
Oh! that's what XorA meant with the dots & dashes. I thought it was morse code. Thanks.

ASCII Art, was used in the old pre-ANSI BBS days when all that was available was a text based terminal.

A bit like this Forum.

ANSI screens like in QLTERM, QTPI etc ... allowed very limited colour graphics.

Posted: **Fri Oct 29, 2021 10:28 am**

Derek_Stewart wrote:Once switch is pressed a high signal is passed to each transistor which switches on each keyboard line.

Look up ^

Posted: **Fri Oct 29, 2021 1:17 pm**

Ruptor wrote:
Derek_Stewart wrote:Once switch is pressed a high signal is passed to each transistor which switches on each keyboard line.
Look up ^

Yes, same solution, over 30 years later.

I first looked for a 4pole keyboard seitch, which werenot made in 1992.

I tried to modify MX style switch to accept 4 wires, switching 2 separate lines. This nearly worked, but not very stable.

So my solution back then was to fit 2 transistors, or as previousily stated "FETS"... to the comverted Memotech MTX512 keyboard which housed a QL board with Trump Card, later on a Super Gold Card.

Posted: **Mon Nov 08, 2021 9:43 pm**

Still have a lot to do, but at last the keyboard is working.
I'm not happy with the keyboard connectors, so I'll have to build new ones.
And not happy with decals I bought for the keyboard - if anyone knows where to buy some decals with large arrows, QL style, please let me know.

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