velocity sensitivity - how does it work?

[diezdiazgiant]

How does it work? Is there a way to implement it into an arcade mod?
If the microcontroller is able to recognize, recieve, and transmit this info - there's got to be a way to implement it in an arcade button

[mastercon12]

there is absolutely no way to add velocity sensitivity to an arcade mod. They are just buttons.

[diezdiazgiant]

Uh huh well as insightful as that was, no offense, I don't believe you.
they're just momentary switchs and when I look at, for an example, the pcb under the keys of a emu xboard 49 its clearly just a basic contact switch. The same is true with an akai mpd16.
Both are just basic contact switchs.

So unless you are able to define what facet of the switch makes velocity information possible I would prefer not to hear your kurt uninformative answers

[charo]

its kind of like asking if you can turn a lightswitch into dimmer switch

you mentioned you see the arcade buttons are momentary on/offs, they are either on or off, and there is no more distinction being made.

pad controllers like the mpd don't use the same simple momentary components.

[diezdiazgiant]

I understand you can't turn the light switch into a dimmer switch but obviously there are dimmer switchs that LOOK like regular switchs.
And considering all an arcade button is is a springloaded piece of plastic over a switch, I do not believe its impossible with extra stuff to make the necessary changes.
Velocity sensitive game pads clearly exist, and if a company can make it so can I or anyone else in theory. Its not magic.


Now does anyone have any actual insight into HOW velocity sensitivity works? is it 2 parallel circuits that can measure the time elapsed between the first circuit and the second circuit closing? That would be my first guess. Considering how cheap you can get a controller with velocity sensitivity it must not be that complex if you know the basic mechanism behind it.

So does anyone have any real information on the matter? In fact just forget I said the words "arcade button", I just want someone to explain what part of the key circuit takes that information and how is that information generated?

[mastercon12]

the mpd 16 doesnt have basic contact switches. All the arcade button is doing is completing a circuit. The mpd pads are detecting velocity and sending out different midi data depending on how hard you hit the pads. If I remember correctly, they act similarly to a potentiometer.

[diezdiazgiant]

Ah thank you mastercon, that was going to be an idea thrown out there - does it work like a lightdimmer where all the dimmer does is inhibit the amount of voltage coming thru. The amount that comes thru is the basis of the value like a potentiometer.

[Fatlimey]

There are four parameters of a full MIDI key event - channel, pitch, velocity and aftertouch. Velocity is a measure of how fast a switch was pressed, so it requires an element of timing. One way is to have two switches set apart with a standard short "travel" distance. As soon as the first switch is activated start a timer that stops when the second switch is hit and that time is proportional to the velocity.

Aftertouch measures how "hard" a button is pressed once it has been activated and is a measure of pressure. These can be done using rubberised resistors that reduce resistance the more they are pressed (e.g. conductive foam being compressed and making a series of shorts through it's volume).

There is a third way and that's the rubberised contact. You can see these on the bottom of Monome -style rubber keys.



As these rings press on the PCB contacts, they conduct more the harder they are pressed. If you sample the voltage across the switch fast enough and graph this over time you get a nice curve. From this curve you can deduce velocity by measuring how much time it took for the voltage to go from zero to a certain threshold value as speed of a hit is often proportional to how hard it was hit (not always so this is really an approximation...) and the aftertouch is just the value of the curve after the threshold has been passed. That's how the MPD pads work.

[diezdiazgiant]

Sweet, thanks limey. So that's why the contact on a 49 key keyboard has 2 contacts for the switch.
Time to see how well those keys take to a dremel drill...

[CerebralExcretion]

Are you trying to modify an existing controller or is this a new DIY project? piezo buzzers are cheap, make very good velocity sensitive switches and their allot easyer to impliment than two switches along with a complex algorithem on a PIC.

Thinking about it i bet you could mount a small piezo in the underside of an archade button then you would have the appearance and playability of an arcade button with the velocity of a drum pad. Hmm i like the idea of that ill order some parts and have a play.