Creating Wilf Rigter's ZXKBD v3

[mrtinb]

I would like to say that all power lines should be much thicker.
kind regards Paul

I'm n00b with electronics. Do you mean all lines, or e.g. 5V and GND?

/Martin

[Paul]

5V and GND only.
For the rest: the thinner the better.
I always choose minimum allowed (by my PCB manufacturer) thickness for all lines except power.
GND normally is "the rest of the PCB" on top and bottom side as it can't be thick enough.
power supply (12V, 5V, 3.3V etc) as thick as the design allowed. Typically 1.27 or 2.54 mm.
Which software do you use? Maybe I could show you some beginner tricks?
kind regards Paul

[mrtinb]

Which software do you use? Maybe I could show you some beginner tricks?

http://fritzing.org

/Martin

[mrtinb]

5V and GND only.
For the rest: the thinner the better.
I always choose minimum allowed (by my PCB manufacturer) thickness for all lines except power.
GND normally is "the rest of the PCB" on top and bottom side as it can't be thick enough.
power supply (12V, 5V, 3.3V etc) as thick as the design allowed. Typically 1.27 or 2.54 mm.

Valuable information. The main problem is to make it fit in the board without getting the board too big. Somehow the software does not support lines between solder points on the expansion connector, so every connection from the expansion connector has to go "around the corner".

/Martin

[PokeMon]

Fritzing is not really software for PCB production.
The result is really poor and it did not change much between my test of Fritzing 3 years ago.
I would recommend to use the free software DesignSpark, easier to handle than KiCAD.
Both are with no limitations in board size, components, via's or tracks.

Anyway doing PCB's needs some experience as well. I think your board will probably run if there is no bug in schematics. You may add capacitors under the IC's (solder side) manually some 100nF ceramic capacitors which will solve the problem with smaller tracks for this application.

[1024MAK]

@ Martin

What Paul says is correct and best practice. Although for a small board like yours that only uses two low power chips, it should be okay. So don't worry too much if you cannot widen all of the +5V and 0V (GND) tracks. Just do the parts that you can.

Pokemon is suggesting adding 100nF (0.1uF) ceramic capacitors directly connected between the +5V (VCC) and 0V (GND) connections of each of the two IC's. As this helps keep the power to the chips stable. As he says, this will help. Having one 100nF ceramic capacitor per IC connected as close as possible to the chips power pins is also best practice.

You are learning and making good progress

Mark

[mrtinb]

You are learning and making good progress

I've learned more a by a couple of days in the forum than the electronics for beginners books I've read.

/Martin

[mrtinb]

Hi

Now the keys from China has arrived. They've been place loosely on top of a pcb. The keys are small 1.2 x 1.2 cm, and the transparent plastic can be opened up, og a small piece of paper can be place under the transparent plastic. E. g. look at the key with Q.

This will be a small keyboard with 50 keys. 10 x 5.

IMG_0046.JPG

(762.97 KiB) Downloaded 433 times

My idea for the layout is this:

Code: Select all

 1  2  3  4  5  6  7  8  9  0      <x SHIFT, 0            ed SHIFT, 1      >  SHIFT 8
 Q  W  E  R  T  Y  U  I  O  P      ^  SHIFT, 7            gr SHIFT, 9
 A  S  D  F  G  H  J  K  L <x      nl NEW LINE            sp SPACE
 Z  X  C  V  B  N  M  ^  . nl      sh SHIFT               <  SHIFT, 5
sh fn ed gr sp sp  <  v  > sh      fn SHIFT, NEW LINE     v  SHIFT, 6

/Martin

[mrtinb]

Code: Select all

 1  2  3  4  5  6  7  8  9  0      <x SHIFT, 0           ed SHIFT, 1      >  SHIFT 8
 Q  W  E  R  T  Y  U  I  O  P      ^  SHIFT, 7           gr SHIFT, 9
 A  S  D  F  G  H  J  K  L <x      nl NEW LINE           sp SPACE
 Z  X  C  V  B  N  M  ^  . nl      sh SHIFT              <  SHIFT, 5
sh fn ed gr sp sp  <  v  > sh      fn SHIFT, NEW LINE    v  SHIFT, 6

As pointed out to me earlier, the keys can't be used for multiple keys, as that needs two separate switches inside the key.

The first version will only have these keys:

Code: Select all

 1  2  3  4  5  6  7  8  9  0
 Q  W  E  R  T  Y  U  I  O  P
 A  S  D  F  G  H  J  K  L
 Z  X  C  V  B  N  M     . nl
sh          sp sp          sh

[siggi]

As pointed out to me earlier, the keys can't be used for multiple keys, as that needs two separate switches inside the key.

Using a transistor or an analog switch, one key can "press" multiple ZX81 key at once.
Here is an example I use to have "Backspace" (BS) and "/" on a single key:

http://forum.tlienhard.com/phpBB3/viewt ... sten#p8838

Regards
Siggi