Re: Good keyboard
On 2/11/16, Martin Smith <lists@rakupottery.org.uk> wrote:
> On 11/02/2016 06:22, rlharris@oplink.net wrote:
>> The essence of a keyboard is found in the keyswitch -- the plunger and
>> the contacts.
>>
>> A good plunger is not lubricated and does not bind even if the key is
>> struck at an angle. Any external lubricant eventually wears through.
>>
>> Good contacts do not bounce.
>>
>> Good contacts do not fail because of oxidation or exposure to common
>> atmospheric contaminants such as moisture, ammonia, and oil vapour.
>>
>> Gold is not necessarily the best contact material for very low voltage
>> and
>> current, because oil vapour can form an insulating film (a polymer, if I
>> recall correctly) on gold. I think that it was Honeywell which published
>> a report on this matter. For a quality keyswitch, a wiping silver
>> contact may be a better choice.
>
> Rhodium may be better, but probably a lot more expensive, we used it a
> lot in difficult conditions
> at sea and in other dirty environments, even in the 70's it was about 3
> times the price of gold, but reckoned to last for years
The previous thread was a good one - I think I saved it. I'm typing this on
one of my old clicky IBMs. Love 'em to death.
Not all keyswitches use(d) electrical contacts. My first keyboard, back
in the mid-70s, was a surplus item made by Microswitch that used
Hall-effect switches and I had to make my own encoder for. Not tactile,
but reliable as the day is long, and no debouncing required. Over the
years I also had a few Keytronics (including one in the Sol) that used
capacitive switches. Again, not bouncy, but in the long run not reliable
either - as the foam pad between the plunger and the little dielectric pad
aged, the force it contacted the underlying PCB pads with dropped and
it stopped registering the keystrokes. I've been meaning to look around
again and see if there are still any replacement pads out there for that
thing.
Jonathan
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