Model F Mod Log

[lowpoly]

the plates are connected by sliding tabs. one of the tabs is longer, and bends to lock the plates together.

Thanks. I guess just bolting them together would be easier then. The curvature makes it more difficult because of the tension from the pcb. Unless there is a way to perma-bend that too.

Bending sheet metal is done with three cylinders:





^^^ There are much smaller machines than these. A machine shop shouldn't be too hard to find near you. emachineshop may be able to do this as well. IIRC, you can add text to your CAD drawing requesting additional machining steps.

Here's a small one:



Page with more pics (site in german):

http://www.top-maschinen.de/biegen-kanten/biegemaschine-quantum-bm3/index.htm

[msiegel]

wow, those are awesome

the pcb is fairly thin, and is held flush against the backplate by two metal pins:




it attaches via these mounting holes:




since the pcb gets the same curvature as the plates, i believe there is a consistent pressure across its face (between the pcb and the barrels that lay on top of it).

[lowpoly]

Do the barrels apply additional pressure to the pcb?

[msiegel]

Do the barrels apply additional pressure to the pcb?

yes, this seems to be one of the reasons for the foam above the barrels.

also, the bottoms of the barrels are slightly curved, not flat -- so they match the pcb curvature.

the layers are:

top plate
foam
barrels
pcb
dielectric film
backplate

[msiegel]

Wondered about that.  I think the rubber mousepad type stuff might be a good substitute.  Cutting all the holes wouldn't be much fun though.   I have some really old mouse pads around here that look bad but aren't coming apart.

it's an interesting problem. the best material would compress well and be resilient, like an open-cell foam, but not fall apart like one

ibm engineers coated one side of the foam pad to seal it off -- the side that touches the barrels. closed-cell foam wouldn't compress well enough, so their choice seems like a good compromise, given the materials they could choose from at the time

i'm not looking forward to cutting holes

[msiegel]

Capacitive Pads

Let's see if we can figure out how these pads work...

*pulls out mr. blurryphone*


for each keyswitch, the front side of the pcb has 2 pads and pair of dots. they're all covered with solder mask, so they are not conductive. the hammer fits over these pads; it is turned away from them when a key is up, and turned against them when a key is pressed.

shadows of some heavy traces are visible through the pcb.




*flips pcb around*


the back side has a single pad bordered by traces, placed in exactly the same location as one of the front pads. it is also covered with solder mask.



...

[msiegel]

on the front side of the pcb, one of the two pads in a pair connects to a trace, while the other pad "floats" on the board, unconnected to any traces.

the back side pads are located directly below the floating front-side pads. the traces bordering back side pads are connected to ground. a ground plane borders the entire pcb.

traces on the front and back sides are thin and cross at right angles. this would minimize capacitive coupling between them.

edit:

the matrix has 16 columns and 8 "rows".

[msiegel]

on the front side of the pcb there are pairs of pads. one of the two pads connects to a trace, while the other pad "floats" on the board, unconnected to any traces.

on the back side of the pcb, there is only one pad per front-side pair. the back side pads are located directly below the floating front-side pads.

traces on the front and back sides are thin and cross at right angles. this would minimize capacitive coupling between them. the traces bordering back side pads are connected to ground. a ground plane borders the entire pcb.

from counting the traces entering each side of the pcb, the matrix can be seen to have 16 columns and 8 "rows". traces for rows are on the front side, and traces for columns are on the back side.

[msiegel]

Hey guys,

I need to fill in some blanks in my modified Model F layout...

so I'm looking for these Model M keys in original colors, their accompanying barrel-inserts, and any stabilizing bars:

• Backspace (plus its insert)
• Tab
• \ (backslash)
• Enter (U.S. version, plus its insert)
• Ctrl
• Alt
• Spacebar

I'd prefer one-piece keys if possible. I do need Alt & Ctrl to be original width rather than the narrower Unicomp 104 width.

What do you guys think is the least expensive way to obtain all these? :)

[msiegel]

$6 nonfunctional on Ebay.  Shipping seems high so maybe if you email him you can talk him down.

The inserts are the problem.  You have to get a keyboard for those.

thanks ripster... & that's a good point: shipping for a whole KB is much higher than for a few keys

hmm...

[ak_nala]

Also, that keyboard being a 1391401 from 1989 almost certainly has stabilizer bars instead of inserts and, of course, two-piece keys.

You would need a later model to get both one-piece keys and inserts, though you could get inserts in a later Blue Label 1391401 if you don't mind two-piece on the non-insert keys.

[msiegel]

Also, that keyboard being a 1391401 from 1989 almost certainly has stabilizer bars instead of inserts and, of course, two-piece keys.

You would need a later model to get both one-piece keys and inserts, though you could get inserts in a later Blue Label 1391401 if you don't mind two-piece on the non-insert keys.

thanks ak_nala

it looks like keys with stabilizer bars probably will work -- *if* the bars are mounted facing toward the user rather than away ...i couldn't quickly find a photo of them around here

i'll still need the inserts, but other than that i'll take what i can get

[kishy]

Just a thing about the pictures...

If your phone has a "macro mode" or an option or switch which has a little flower icon, use it. It allows for better quality closeup shots.

I haven't seen a camera phone yet that doesn't have the feature...it's usually hidden pretty well though.

[msiegel]

If your phone has a "macro mode" or an option or switch which has a little flower icon, use it. It allows for better quality closeup shots.

thanks kishy

hmm... reviews indicate mine doesn't have autofocus *or* macro mode
it's an old Nokia E65.

[msiegel]

this requires patience

[msiegel]

om nom

[msiegel]

Sorry to get back onto the whole foam thing but it looks like the holes are keyed so the foam really doesn't even hold the wells in place.  More sound insulation than anything else.

the side of the top plate that faces the wells is not perfectly smooth -- there are some protrusions from plastic stabilizers which are riveted through additional holes in the plate.

the foam not only cushions wells against the top plate, with the pressure and friction providing a more secure mount, but also greatly improves the tolerances for assembly.

any sound dampening might just be an added bonus.

[msiegel]

updated layout, with modified top plate illustrated (dark gray)

blue keys are model m replacements (on order from clickykeyboards)
yellow keys are for cursor control, Up Left Down Right

it will be small, because there's no case

[msiegel]

Nice layout.  It looks like it will be tricky getting everything aligned - after my N52 mod I appreciated the small tolerances involved.

thanks

the existing cutouts should work for all but the bottom row. yeah... we'll see about aligning things with 1/10 mm accuracy

[msiegel]

parts arrived today from clickykeyboards!

the backslash, enter, alt, and space bar are replacement keys from model m, to fill in blanks in the new layout.

the entire layout is shown here loose. the keys are not attached to anything yet...

this layout features:
- caps lock = Function
- num lock = "logo" (windows/opt),
- the original number-pad arrows,
- esc & backspace are in ansi-like positions at the corners of the board
- alt and space bar are in same locations as on model m
- no missing characters for u.s. users

apparently this is model 8426

[Mnemonix]

this layout features:
...
- the original number-pad arrows,

Very nice!  The arrangement of the arrow keys reminds me of my old Commodore 128.
Checked a picture... the sequence was a bit different on it: Up, Down, Left, Right.

[Shawn Stanford]

This thread is teh ****e!

[msiegel]

Is the pad active next to the Rshift key?   I still like the traditional T style better.  It  would be offcenter by a 1/4" but still not bad.

My Model M International has that pad active.

thanks... reminds me to put a pad under every barrel, when i make the new pcb

[Shawn Stanford]

...snip... this layout features: ...snip...

Show Image

Where are Ins, Del, Home, End, PgUp & PgDn?

[msiegel]

Where are Ins, Del, Home, End, PgUp & PgDn?

good question!

the keymap will be user-definable...

i imagine:
Del = Function + Backspace
Ins = Function + ~
Home, End, PgUp & PgDn = Function + arrows

[Shawn Stanford]

So, the attention keypress will be (for instance) Ctl+Alt+Fn+Backspace?

[msiegel]

So, the attention keypress will be (for instance) Ctl+Alt+Fn+Backspace?

XD heck, i don't know...

that one might call for a user-defined macro


edit: but yes, that's correct in the scheme i'm currently imagining

[ch_123]

OK, here's a pic from Chloe showing those pins poking through the foam in a XT Model F.

On the AT Model F, there's no foam on the top plate. Only between the two plates, so most of it is unexposed and in good condition.

[msiegel]

On the AT Model F, there's no foam on the top plate. Only between the two plates, so most of it is unexposed and in good condition.

right, that shot shows what's under the top plate

[msiegel]

Everything looks pretty similar from the F AT vs F in the pics except the metal back plate and the notches in the plate are in a different part relative to the circle.  Controller obviously.  Wonder if springs/hammers are the same?

yes, they're quite similar.

the top plates have a different surface treatment: painted on the XT, and what looks like black oxide on the AT.

the hammers are slightly different in shape, as are the barrels (one difference being those notches you mentioned).

not sure about the springs. one day i'll have to get a set of XT springs/barrels/hammers to compare and build with


on an unrelated note, the switch modules from (3) 122-key model F terminal boards could be used to build (5) of these mini keyboards

[msiegel]

Is the pad active next to the Rshift key?   I still like the traditional T style better.  It  would be offcenter by a 1/4" but still not bad.

hmm... if you did that, then the ~ could be moved to the lower right corner of the board, and a standard double-wide backspace would fit in the top row

[JBert]

Everything looks pretty similar from the F AT vs F in the pics except the metal back plate and the notches in the plate are in a different part relative to the circle.  Controller obviously.  Wonder if springs/hammers are the same?

One difference I've found is that the backplate of the key assembly is a lot more "loose", i.e. you can slide it open by hand and the barrels can still move a bit when the thing is assembled. Compare this with an XT where I needed a hammer to shift the plates and where the barrels are clamped down.
Maybe as a result, you get the different key feel like a de-revetting model M compared to a complete one.

[msiegel]

making progress, slowly and steadily

[lowpoly]

Maybe use a Dremel?

[chimera15]

Really interesting.  What are you using for the electronics of it?  The same controller?

[msiegel]

Really interesting.  What are you using for the electronics of it?  The same controller?

the controller is a Teensy mini AVR development board, which will be running open-source GEEKey software.

this mod will also use a homemade capacitive sensor PCB, thereby replacing all of the Model F's original electronics

[chimera15]

the controller is a Teensy mini AVR development board, which will be running open-source GEEKey software.

this mod will also use a homemade capacitive sensor PCB, thereby replacing all of the Model F's original electronics

So cool,  I have to get one of those teensy's.

I'll have to look up GEEKey, thanks a bunch.

What's the capacitive sensor going to do?

[msiegel]

What's the capacitive sensor going to do?

the capacitive matrix pcb senses whether each key's hammer is in the down or up position (close to, or far away from, the pcb)... in order to register keypresses.

this is similar to the model m's membrane sheets, but instead of relying on the conduction (or not) of electricity, it uses "capacitive coupling" of a test signal:

if a hammer is close to the pcb, a test signal will pass through sensor pads and be detected; but if a hammer is far away, the signal is blocked.

[msiegel]

This is where it gets interesting.  How are you going to reverse engineer a Model F capacitive circuit??

operation of the sensor matrix seems very straightforward, which leads me to believe the circuit is so simple it does not even use an oscillator.  

so far the theory is:

row traces are on the pcb's front, and the controller chip applies test pulses to each row. column traces are on the pcb back, connected to a few (inverter?) chips that clean up any test pulses that make it all the way through to the rear pads. then the pulses (if they made it through) are read by the controller chip.

no diodes

it looks like all the hard work is being done by capacitive coupling between the two front pads, mediated by the hammer.  the magic of capacitive coupling is also used to pass the signal *through the pcb* from the second "floating" (electrically unconnected) front pad, to the back-side pad.

[chimera15]

the capacitive matrix pcb senses whether each key's hammer is in the down or up position (close to, or far away from, the pcb)... in order to register keypresses.

this is similar to the model m's membrane sheets, but instead of relying on the conduction (or not) of electricity, it uses "capacitive coupling" of a test signal:

if a hammer is close to the pcb, a test signal will pass through sensor pads and be detected; but if a hammer is far away, the signal is blocked.

Do you have to do that because the teensy won't register the electrical connection or something?  Why not just use the normal matrix?  Oh because you ruined the matrix when you hacked the board apart?  Why not just rewire it? Or it's easier to do it this way?

[msiegel]

Do you have to do that because the teensy won't register the electrical connection or something?  Why not just use the normal matrix?  Oh because you ruined the matrix when you hacked the board apart?  Why not just rewire it? Or it's easier to do it this way?

ideally i want to gather enough information, materials specs, cad files, source code, assembly techniques etc... so that keyboards based on model f technology can be manufactured again, in a modern and affordable form.

[chimera15]

ideally i want to gather enough information, materials specs, cad files, source code, assembly techniques etc... so that keyboards based on model f technology can be manufactured again, in a modern and affordable form.

So you're using that method so that you can manufacture it down the road, not for any practical reason?

[msiegel]

So you're using that method so that you can manufacture it down the road, not for any practical reason?

practically, the bottom row of the original pcb doesn't match the new compact layout, and there are too many rows+columns for the Teensy controller

[chimera15]

Ah that's interesting.. how many keys will the teensy support?

[msiegel]

Ah that's interesting.. how many keys will the teensy support?

i'm planning a 15x5 matrix (using 20 pins), and saving a few more pins for an rgb led...

a maximum of 75 keys are possible in this configuration.

the compact layout i have in mind only includes 66 sets of sensor pads though

[Mnemonix]

i'm planning a 15x5 matrix (using 20 pins), and saving a few more pins for an rgb led...

Great to see progress here!

A 15x5 matrix will be quite dense and introduce a lot of possibilities for ghost keys to occur; at least on a conductive matrix w/o diodes this would be the case. If there is no connection between the pads, there is no way for ghosting on a capacitive matrix, right? That would be quite cool, actually.

Otherwise I would be a bit worried about the Function key you wrote about somewhere because it needs to be detectable in any key combination, thus requiring a row of its own.

EDIT: A 12x8 matrix seems attractive, too. It would allow for 96 keys and looks nicer from a software point of view.

[msiegel]

A 15x5 matrix will be quite dense and introduce a lot of possibilities for ghost keys to occur; at least on a conductive matrix w/o diodes this would be the case. If there is no connection between the pads, there is no way for ghosting on a capacitive matrix, right?

yes, this is still an open question... although there's no conduction path between "switches", i don't know whether there's still a way they can interfere with each other.

i plan to test this. hopefully a 2x2 matrix made of cardboard and aluminum foil will be good enough to know for certain

[JBert]

Well, your research can also be handy for buckling beam keyboards in case those need a new controller board.

[Mnemonix]

i plan to test this. hopefully a 2x2 matrix made of cardboard and aluminum foil will be good enough to know for certain

I'd guess so.

Great, now I want a Model F, too. Congrats.

[microsoft windows]

I never knew Model F's had green Alt keys.