Another KeyTronic F&F with CommonSense

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OldIsNew

03 Dec 2019, 07:09

I recently came across Sangdrax's very nice write up of his General Rad KT F&F board - 1983 General Radio / Gen Rad LM2 (vintage tall keytronic) - and figured it was about time I tried CommonSense with one of my F&F boards too. Sangdrax covered things nicely in his post so I'm going to be fairly brief as far as redoing the board itself.


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It was the usual replace the rotten F&F:
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Wired up the Cypress:
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and TADA!!



Well actually ...

It definitely took me some fiddling to get the basics of CommonSense, especially since I've never played with PSoC Creator before. As I think DMA may have remarked - READ THE DOCUMENTATION. I really found snacksthecat's guide very helpful too!


One notable thing on my board was that key presses do pull up keys in the same row on adjacent columns - more so downstream than upstream - for example pressing a key on column five might pull up the key on column four by 6, the key on column three by 4 and the key on column two by 2. Less effect upstream with the key on the next upstream column bumping 1 or 2 and no changes above that column.

This caused me a bit of a problem in a few spots - probably due to variation in my homemade F&F - where occasionally a key press on an upstream column would would pull up an adjacent key on that row beyond the maximum value reached when pressing the adjacent key itself - making it hard to set thresholds. At first I wasn't sure if this was a wiring issue but I did see that Sangdrax noted something similar a well:
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It was mainly a matter of fiddling around with the F&F disks to get around this - again I suspect that inconsistencies in the thickness, etc. of my hand cut F&F disks was largely contributing this issue.

Another big thumbs up for DMA's CommonSense from me and I know I'll be using it more in the future.

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XMIT
[ XMIT ]

03 Dec 2019, 21:31

Excellent!

I wonder, how well would these F&F boards work replacing the foil with conical springs? That might make things a bit more consistent.

I have an old Sperry F&F board that I'd like to convert now...

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snacksthecat
✶✶✶✶

03 Dec 2019, 21:36

XMIT wrote:
03 Dec 2019, 21:31
I wonder, how well would these F&F boards work replacing the foil with conical springs? That might make things a bit more consistent.
"Hey guys, look at my 1977 Topre."

Also, darn you for putting this idea into my head.

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Sangdrax

03 Dec 2019, 21:37

Topre springs should click right into the 11mm holders, no mods required. The problem is acquiring them in bulk at a non-topre price. I've never had the luck to find their souce. Plus you'd have to lacquer the boards with bare metal pads I suppose.

Nice work on the board, OldisNew. Always love seeing the stuff you find and bring back to life.

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ZedTheMan

03 Dec 2019, 23:50

Darn all three of you for making me want to do something with my F&F board now....

We gotta find those topre springs, yo.

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XMIT
[ XMIT ]

04 Dec 2019, 16:51

Surely we can find a Chinese vendor who will make and sell them on the cheap. It's just coiled steel, after all.

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snacksthecat
✶✶✶✶

04 Dec 2019, 16:56

I actually just bought a Plum keyboard that was for sale with no caps or domes. Seemed like a good candidate to pull springs from (I presume this keyboard has the conical springs, right?)

I'm sure there's stuff that pops up on tao bao but I'm no good at finding things on there.

This should be a fun little experiment, thanks for the idea.
Sangdrax wrote:
03 Dec 2019, 21:37
Plus you'd have to lacquer the boards with bare metal pads I suppose.
Hi Sangdrax, good to see you again. This part wasn't clicking with me. Mind explaining what you mean?

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XMIT
[ XMIT ]

04 Dec 2019, 17:58

snacksthecat wrote:
04 Dec 2019, 16:56
Sangdrax wrote:
03 Dec 2019, 21:37
Plus you'd have to lacquer the boards with bare metal pads I suppose.
Hi Sangdrax, good to see you again. This part wasn't clicking with me. Mind explaining what you mean?
What happens when you put a conductive metal spring across exposed copper capacitive pads?

I'd use Kapton polyimide tape here, it's thinner, neater, and more consistent than lacquer.

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snacksthecat
✶✶✶✶

04 Dec 2019, 18:13

Oh duh, it's like when I put the conductive side of the space blanket disks down instead of up last time when I fixed up one of these keyboards.

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