double action switch

[Semaj]

I'm trying to build my own keyboard.

I've been looking for a double action switch to use in a key board that will let me be able to press a key with a small/normal amount of force for normal key presses, but I want to then be able to trigger a different action by pressing the key harder, and use this action as a shift-key press action. Does anyone here know of a switch that works like this that I could use?

At the moment I'm thinking I might just have to use pressure sensors on the keyboard feet and calculate when the user presses hard on the key board, this would mean I could adjust the pressure needed for the second action, but I wouldn't have any haptic feed back then.

[Arcanius]

I haven't heard of any such keyboards, it's unlikely they exist, due to the complexity that would be involved. Even making a controller for one of these would be pretty expensive.
The pressure sensors may work, but I doubt it's ideal.
Have you thought of a footswitch, or using shift, but remapping it to a more ergonomic position?

[kps]

IBM patented a beam spring switch like that; I don't know whether they sold any keyboards with it.

[martinmeijerink]

Maybe you have to look at the Commodore 64's RESTORE-button. If you press this key with the same force as a regular key, nothing happens.
Mechanically the key is the same as all other keys, but due to a (intentionally) cascade switched capacitor, you had to press this key really hard before something would happen.

[The Solutor]

Obviously those switches exist, they are present in any autofocus camera or cameraphone, but I doubt the idea was ever used on pc keyboards.

[theferenc]

The only double action switch I'm aware of that is readily available is the trigger assembly in many hand guns.

You may have to use nested switches, or some such, similar to how cameras work. At least autofocus every camera I've ever taken apart, there are actually 2 switches under the shutter release, one low force that activates the focus, one high force that releases the shutter.

Another idea would be stacked switches, with enough initial resistance that the first switch wouldn't descend onto the second switch until it was bottomed out. You'd have lots of issues with that, including ignoring the first key press (possibly using break codes), stability on the top switch, and making sure the top switch doesn't release first.

But still, could be doable.

[The Solutor]

At least autofocus every camera I've ever taken apart, there are actually 2 switches under the shutter release

Same of them are builth with two separate switches, but not all.

The double action switches are in production purposely for that kind of application

http://news.thomasnet.com/fullstory/Double-Action-Switches-provide-150-000-cycle-lifespan-596722