Velocity Sensitive Touch Pad

[transistance]

I have comprehensive and practical knowledge of resistive and theoretical knowledge of capacitive touch pads. I was wondering if there are velocity sensitive touch pads out there.

I'm guessing if they do exist these pads will be impossible to recreate in home based workshop - kind of like the capacitive touch pads (or are those feasible?)

Just want your input, if it is not out there, I want to start a constructive discussion as how to it could be built.

 

[transistance]

Just a thought: would this be possible by implementing a piezzo array below the capacitive/resistive layers? Can piezzos be built small and thin enough?

 

[ericgibbs]

Just a thought: would this be possible by implementing a piezzo array below the capacitive/resistive layers? Can piezzos be built small and thin enough?

hi,
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[prprog]

I have comprehensive and practical knowledge of resistive and theoretical knowledge of capacitive touch pads. I was wondering if there are velocity sensitive touch pads out there.

I'm guessing if they do exist these pads will be impossible to recreate in home based workshop - kind of like the capacitive touch pads (or are those feasible?)

Just want your input, if it is not out there, I want to start a constructive discussion as how to it could be built.

Can you explain the term "velocity sensitive touch pads"?
Is this the same as pressure sensitive touch pads?

Thanks,

 

[transistance]

Not sure, i don't think so though.. It should involve some kind of acceleration sensor the way I'm thinking. Kind of like how modern synthesizers' keys.

 

[prprog]

Not sure, i don't think so though.. It should involve some kind of acceleration sensor the way I'm thinking. Kind of like how modern synthesizers' keys.

..for what I know synthesizer keyboards determine velocity value (MIDI information) by sensing 2 switches. The closure time difference between the 2 switches determine the velocity (volume) value. Is this what your are looking for?

Is there a synthesizer that used an acceleration sensor?

 

[ikennaobi]

solution for my dell laptop

please i have a dell laptop pentum m d600 and it is not charging the battery, but the computer is working properly. the only problem i am facing now is that is it not charging the battery, i need a solution and the laptop diagram.

 

[Torben]

please i have a dell laptop pentum m d600 and it is not charging the battery, but the computer is working properly. the only problem i am facing now is that is it not charging the battery, i need a solution and the laptop diagram.

Hello ikennaobi,

Please start new threads when you want to start a discussion. This thread is about something else entirely. Posting an off-topic question in someone else's thread is known as "thread hijacking" and just confuses things.

At a glance, it sounds like your laptop battery has just gotten too tired to hold a charge anymore. As far as I know the only solution is to buy a new battery.


Torben

 

[transistance]

..for what I know synthesizer keyboards determine velocity value (MIDI information) by sensing 2 switches. The closure time difference between the 2 switches determine the velocity (volume) value. Is this what your are looking for?

Is there a synthesizer that used an acceleration sensor?

2 switches make more sense, but I'm guessing it is also the reason behind having cheaper and more expensive synthesizer keyboards possibly. Since having individual accelerometers in my opinion will give better continuous data, and will cost a lot more.

 

[Nigel Goodwin]

2 switches make more sense, but I'm guessing it is also the reason behind having cheaper and more expensive synthesizer keyboards possibly. Since having individual accelerometers in my opinion will give better continuous data, and will cost a lot more.

I don't think any do such a crazy thing - two switches works perfectly - I don't see as accelerometers would improve it, quite the opposite probably as it couldn't detect a held down key.

 

[Torben]

I've heard of the two switches thing and others which use FSR (the two switches method does not allow for aftertouch). I've never heard of accelerometers being used.

Then again, I've never made a keyboard. I've cleaned lots of them, though.


Torben

 

[brett2010]

If I wanted to measure the length of time a key was pressed, I would use a microprocessor, which can be programmed to measure times. However, this does not fully address the velocity question. The microprocessor approach can measure length of depression at microsecond precision - can you somehow relate velocity to 'depression time'?

On another line of thought, I built a velocity measurer, based on 2 laser beams. When they were broken and remade, velocity was measured using pretty simple microprocessor code. This does not seem practical in your application, but perhaps a variation of it would work. I am thinking of a user-built keyboard, with 3 layers of foil, and button cutouts. When pressed, the first contact would be between layers 1 and 2 of the foil, and then layer 3. The speed beteen layers 1, 2 and 3 would give you a key press velocity. The theory is sound but I wouldn't care to have to make it.

=OR= How about a keypad with break before make contacts? The break time would be measured, also giving velocity.

 

[Torben]

If I wanted to measure the length of time a key was pressed, I would use a microprocessor, which can be programmed to measure times. However, this does not fully address the velocity question. The microprocessor approach can measure length of depression at microsecond precision - can you somehow relate velocity to 'depression time'?

Not that I know of, but if you read the posts in this thread, you will find some other ways to detect velocity. You can use a microcontroller or not--depends on how you want to solve the problem.


Torben

 

[Nigel Goodwin]

If I wanted to measure the length of time a key was pressed, I would use a microprocessor, which can be programmed to measure times. However, this does not fully address the velocity question. The microprocessor approach can measure length of depression at microsecond precision - can you somehow relate velocity to 'depression time'?

On another line of thought, I built a velocity measurer, based on 2 laser beams. When they were broken and remade, velocity was measured using pretty simple microprocessor code. This does not seem practical in your application, but perhaps a variation of it would work. I am thinking of a user-built keyboard, with 3 layers of foil, and button cutouts. When pressed, the first contact would be between layers 1 and 2 of the foil, and then layer 3. The speed beteen layers 1, 2 and 3 would give you a key press velocity. The theory is sound but I wouldn't care to have to make it.

=OR= How about a keypad with break before make contacts? The break time would be measured, also giving velocity.

You seem to be ignoring how velocity sensitive keyboards work?, there are two sets of contacts, one closes before the other - the velocity is very simply worked out by how long the time between the two closures is.

 

[b rett2010]

Re: above comment

The switch would need to be a changeover switch - and you measure th time between the NC contacts opening and th NO ones closing

 

[Nigel Goodwin]

Re: above comment

The switch would need to be a changeover switch - and you measure th time between the NC contacts opening and th NO ones closing

No, it doesn't have to be at all - two separate switches are all you need, and they are usually both normally open, with separate feeds to the controller.

 

[continentalrocket]

Hey there!

I'm just about to modify a MIDI controller that has velocity sensitive pads(the ones you guys are talking about.) to change it to buttons that respond much quicker. I'm a DJ, so I don't need velocity sensitivity, I'd prefer speed. The thing is that I'm not sure if the swapping would work because of the velocity sensitivity. So I checked the inside and all i saw was two films one on top of each other, just like the ones you'd find inside a computer keyboard. So basically each button was working the same way as any other that isn't velocity sensitive. So the idea of having 2 buttons does make sense, but I couldn't find any evidence to support it.
**broken link removed** is a (pretty blurry) picture of the insides of the pad. You can see the cables on the sides of each pad. 1 pair. Not even 3.
**broken link removed** picture shows the back of the whole panel. There is a wide copper film connecting the metal back panel to the pcb, but I couldn't find any actual connection between any wires on the pcb and the copper film.
I hope this helped in your discussion.
If you've got any explanation for this dilemma, please let me know. I'd love to know if replacing the pads with buttons is going to work or am I throwing money out the window

Peace, love and afrogrease,

continentalrocket

P.S.: I hope this doesn't constitute as "thread hijacking", I would've made a new topic, but I thought what I found out would contribute to this discussion.

 

[prprog]

Hi continentalrocket:

Is this one of those Korg controllers? Is there a option to turn off the touch sensitivity or set it to a high/low value? You should try that before any mod. Although it is not a 2 switch "velocity sensitity as old keyboards" it might used capacitance or (resitance) to generate a velocity value. You might check how it works before trying to "bend it".
This way you can add switches that mimic a the "full" resistance or capacitance.

PRPROG

 

[Mr RB]

I recently worked with capacitive touch sensors. They generate a frequency that gets lower with the closer your finger gets. You can easily implement velocity sensing by sensing the rate of change of that frequency using your software.

It's gonna be a little fuzzy as the freq also depends on finger mass (which finger/thumb) and how hard you press finger on the pad (footprint area), so using your thumb will be detected as a higher velocity for example.

But for simple electronic drum pads i'll bet it can be done.

 

[prprog]

I recently worked with capacitive touch sensors. They generate a frequency that gets lower with the closer your finger gets. You can easily implement velocity sensing by sensing the rate of change of that frequency using your software.

It's gonna be a little fuzzy as the freq also depends on finger mass (which finger/thumb) and how hard you press finger on the pad (footprint area), so using your thumb will be detected as a higher velocity for example.

But for simple electronic drum pads i'll bet it can be done.

Can you post a circuit diagram of your work? I am currently working some test with capacitive touch sensor using the 4066 quad switch IC and some copper plates and different dielectrics.