Hacking keyboard PCBs

[Gavin Gavin]

Has anyone any experience of hacking/mending keyboard PCBs? I’d like to re-purpose just the numeric keypad from a PC keyboard as part of my v annoying alarm clock project. 

I understand that they work as a kind of multiplexed matrix, so depending on the track layout and whether they numeric pad is in it’s own separable matrix, i figured it may be possible to just saw that part off, connect the rows and columns of the pad to an MCU and, hey presto, have a nice numeric keypad with keyboard quality buttons to mount in the top of my clock.

Presumably I would have to carefully scrape off some solder mask to reveal the tracks to connect to. Is there a chemical that removes solder mask to expose the copper? 

btw I know that there are small numeric keypads that you can buy for arduinos, but i’d like the mechanical movement that you get from a proper keyboard.

btw2 I have also seen the 17 key ‘accounting pads’ that you can plug in (quite cheap) but I only want the ten keys with numbers on, so they would need to be similarly hacked too

Gavin

[Tom Allen]

I did this when I was a kid without too much hassle, although taking
other keyboards apart since, they are quite varied inside. To connect
to wires to the tracks on the acetate sheet used super glue! Soldering
was impossible without melting, well when I was a kid anyway. good
luck

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[Matthew Daubney]

I made it onto Make mucking about with these when I was at Uni (although I only found that out recently!). You'll need to take the thing apart to find whether it's a single controller or two (probably one). The control PCB's themselves are quite small in most cheap usb keyboards, so you might find it's no issue.

[Gavin Gaunt]

I've been looking at keyboard tear downs and hacking the membrane looks like it could be difficult, though I see some repair guides that use conductive ink. Ideally I'd open one up and discover that the numeric keypad had its own matrix and I could just cut it and connect onto the ribbon connector. Else it could get tricky.

I've ordered a cheap numeric keypad in case -  I can always just take the keys I don't want off

G

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From: Matthew Daubney
Sent: ‎31/‎03/‎2016 09:13
To: Reading Hackspace
Subject: [RDG-Hack] Re: Hacking keyboard PCBs

[Alex Gibson]

If that one doesn't work out I have a spare usb numerical keyboard, with proper keyboard keys.  Intended to do something similar but it could be years before I get around to it.

For a sure fire solution, it is possible to get replacement key-switches for the older style full typewriter travel keyboards like IBM, cherry etc which have individual key switches. (Or salvage from one if those keyboards) These could be arranged on a simple PCB and wired easily to a Minimus or other small AVR configured to appear as a USB keyboard device...

Tapped on my mobile phone.

[daprigoo]

Cherry keyswitches are very nice. I recently got a mechanical keyboard and had forgotten just how superior they are to the modern membrane types

[Gavin Gavin]

After a failed attempt to hack a cheap, membrane-type numeric keypad, I’m thinking of changing tack and going for mechanical key switches. The switches are not that expensive (~50p a piece) but I’m looking to use maybe 16 of them, and it’ll also cost money to have a PCB made up for them. So:

1) any ideas of how I can lay my hands on cheap switches? Are there any old, but mass-produced computers that used them that I might be able to lay my hands on a keyboard from?

2) Also, any ideas on how to print / put text onto the caps? You can buy sheets of transfers for the numbers, but I was thinking of having other buttons - perhaps with pictures or words on. Being able to choose a nice font for the numbers would be good too.

[Matthew Daubney]

You could 3d print the caps, it's been done a few times I think like these http://www.thingiverse.com/make:131197 or find some blank caps and then laser etch/ink the characters?

[Gavin Gavin]

Am thinking I might 3D print the body of the caps, and top with laser engraved ply (I’m planning to make the case out of wood)

[Alex Gibson]

That would be nice.

You can do impressively detailed marquetry using the laser cutter - repeat the cut using a contrasting wood, glue the numbers or symbols in the space left, then you can sand off the top surface and varnish leaving a beautiful effect.  I do similar with laser acrylic and DCM for logos.

Tapped on my mobile phone.

[Jeremy Poulter]

While clearing out I found an old 'keyboard' with mechanical buttons (at least I think they are). I say keyboard but it is really just a row of additional F keys.

It is in the top draw of you want to take a look, sorry didn't get a chance to take a pic.

Jeremy

PS if it is of no use to Gavin anyone else is welcome to it.

[Gavin Gavin]

Thanks - I’ll take a look later

[Gavin Gaunt]

Have managed to salvage 20/21 of the buttons off of it (Cherry MX Blue). Manoel has the carcass

Cheers

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From: Gavin Gavin
Sent: ‎03/‎05/‎2016 18:13
To: reading-...@googlegroups.com
Subject: Re: [RDG-Hack] Hacking keyboard PCBs