Topre Capacitive Switches and Longevity

[rdjack21]

A rubber dome seems inherently more likely to wear out than a metal spring. The fact that it is the spring, though, and not the rubber dome, that pushes back on the key does mean there is a difference between that design and a membrane keyboard that would attempt to be a good-quality membrane keyboard by using a similar high quality of rubber.

All the rubber dome does is change the key's tactile characteristics.

One could imitate the Topre with a membrane keyboard, then, by adding springs to the keys - and changing the dome design appropriately. Then, the rubber domes would have less work to do, and the difference would be contact switching instead of capacitative switching. But such an imitation would fall short in one important way: even if the spring pushes the key back up, the dome would still have to spring back up by itself (assuming the spring is on the plunger, not inside the dome as in the Topre).

So I suppose an interesting question comes out of this. Were there any spring plus rubber dome keyboards, and were any of them any good, even if not as good as the Topre?

First off lets clear some misconceptions up here.
1) The spring under the dome of the Topre switch provides very little if any of the feel of the Topre switch. Some think that the spring may help stabilise the dome but I'm not even sure it does that. The sole purpose of the spring is to act as the second electrode in the electrostatic capacitive non-contact switch. Go take a look here for a full explanation of the switch.

You are missing the whole point of the Topre switch which is that you do not have to bottom out the key for a key stroke to be registered. I very rarely bottom out my Topre boards even on my short throw board.

There are good rubber dome keyboards on the market but they are membrane based so you have to bottom out the key to register the key stroke. I have a few of them laying around here that I have had for 10+ years and they still feel the same as when I bought them. But very few rubber dome keyboard manufactures will spend the money to make a good rubber dome. Instead they change the geometry of the dome so that it can be stiff but require as little rubber as possible (reduced cost). So really the only way to know for sure if you have a good one is to take it apart and see how it is built. I have done this on quite a few boards and the vast majority of them have thin small domes (cheap) even though the keyboard may cost upwards of a $100 bucks. Then you have the lifetime warranty keytronic boards where all the cost of the board goes into the domes but the case and the keys suffer so it ends up feeling like a cheap board. I really wish they would come out with a high quality board then the only thing that would make the Topre unique would be the non-contact switch. But it is that non-contact switch that really makes them unique and desirable if you want to type fast.

As to your last question yes there have been other keyboards that have mated a spring to a rubber dome but they suffer from the same problem as all membrane based boards you must bottom them out for a key to register.

Fijitsu has also just released the LiberTouch as well that may be interesting to take a look at. But then again at 15,000 to 18,000 yen they are not much cheaper than a Topre and you have to bottom them out as well.

[Hak Foo]

Dell AT101W - $15 for 104 keys = 14.4 cents per key
Model  F AT - ~$100 for 84 keys = ~84 cents per key
Scorpius M10 - ~50 for 104 keys = ~48 cents per key

Considering how little these other keyboards cost in comparison, the Topre boards really have an astronomical price.

The AT101W and F are not current products, so we can't compare fairly-- secondary market pricing is not reliable.

I'm also not sure of the M10.  Did ione withdraw from the market with their tail between the legs since the quality was so poor?  I'd sort of love to buy a three-year warranty on it (noticed Amazon offers one and demand it replaced seventeen times, as my BS-powered Death Fingers smash the PCB into dust)

[skriefal]

That F AT works out to $1.19 per key, not $0.84.

[ch_123]

When in production, Model Fs sold for the rough equivalent of $500 in todays money, which works out at close to $6 per key.

[maxlugar]

When in production, Model Fs sold for the rough equivalent of $500 in todays money, which works out at close to $6 per key.

And worth every god damn penny.

Can you name another piece of office equipment that is just as functional 25 years later?  

[maxlugar]

OK, besides, the Swingline stapler  

[itlnstln]

Paper clips and coffee cups.  You will never be able to replace my coffee cup.

[jcoffin1981]

In all reality the only points of wear on a Topre keyboard are the domes and the key sliders. Topre uses a very high quality rubber for the domes so really no issue there and the same goes for the the key sliders as well.

That may be, but I can understand why this would make people nervous.

A rubber dome seems inherently more likely to wear out than a metal spring. The fact that it is the spring, though, and not the rubber dome, that pushes back on the key does mean there is a difference between that design and a membrane keyboard that would attempt to be a good-quality membrane keyboard by using a similar high quality of rubber.

All the rubber dome does is change the key's tactile characteristics.

One could imitate the Topre with a membrane keyboard, then, by adding springs to the keys - and changing the dome design appropriately. Then, the rubber domes would have less work to do, and the difference would be contact switching instead of capacitative switching. But such an imitation would fall short in one important way: even if the spring pushes the key back up, the dome would still have to spring back up by itself (assuming the spring is on the plunger, not inside the dome as in the Topre).

So I suppose an interesting question comes out of this. Were there any spring plus rubber dome keyboards, and were any of them any good, even if not as good as the Topre?

In all reality the only points of wear on a Topre keyboard are the domes and the key sliders. Topre uses a very high quality rubber for the domes so really no issue there and the same goes for the the key sliders as well.

That may be, but I can understand why this would make people nervous.

A rubber dome seems inherently more likely to wear out than a metal spring. The fact that it is the spring, though, and not the rubber dome, that pushes back on the key does mean there is a difference between that design and a membrane keyboard that would attempt to be a good-quality membrane keyboard by using a similar high quality of rubber.

All the rubber dome does is change the key's tactile characteristics.

One could imitate the Topre with a membrane keyboard, then, by adding springs to the keys - and changing the dome design appropriately. Then, the rubber domes would have less work to do, and the difference would be contact switching instead of capacitative switching. But such an imitation would fall short in one important way: even if the spring pushes the key back up, the dome would still have to spring back up by itself (assuming the spring is on the plunger, not inside the dome as in the Topre).

So I suppose an interesting question comes out of this. Were there any spring plus rubber dome keyboards, and were any of them any good, even if not as good as the Topre?

Yes I realize older thread.  The Dell L100 I belive has rubber domes with springs.  Still requires you to fully depress the keys.  Feels kind of cheap to me, but some really like these.

[quasistellar]

That would, however, mean you'd either have to store some pretty lengthy levers somewhere or end up with a severely heavy keyboard

Nearly all keyboards still have the rows of keys offset sideways from
each other, which was originally to make room for levers.
I'd bet lots of mechanical typewriters used gravity instead of springs
to return the keys.

On the other hand, the keys usually had a lot longer travel than 4 mm,
and probably didn't return very quickly, either.

This is all very true.  I've typed on old typewriters, and you can outpace them easily and make the levers jam.  That's one of the reasons QWERTY layout was invented.