the story so far: searching for a DIY pad solution

lol, xmas come early!

re: scan matrix

it's more likely that they'd do a 4x4 scan, so rows are done by one shift register, and the columns by another (or both by one in fact, given enough inputs).

personally, i think the original pad material did not trigger when broken pieces lay on the contacts, merely because pressure has to be applied with any circuit to make contact (why do you think you have springs holding your AA batteries in your walkman?). also, until someone can confirm that the 'graphite' does indeed change resistance with pressure, i'd be more inclined to think that the varying resistance is provided by the varying surface area of contact of the 'graphite' with the underlying copper tracks when different pressures are applied. reason being that the physical design of the underside of the rubber pad (domed: to provide an increasingly large circular contact point with increaing pressure) and the copper tracks (they are larger than the initial contact point of the pad, if the 'graphite' had variable resistance, there would be two contacts near the middle, rather than spirals) both show this (to me, at least). i may yet be proved wrong (or even it's a combination of the two!).

i'd be more inclined to think that the varying resistance is provided by the varying surface area of contact of the 'graphite' with the underlying copper tracks when different pressures are applied.

if this was the case, tell me what you make of this.

any tiny scrap of tin foil that makes even the slightest connection between the two copper coils of the sensor triggers a 127 velocity note, regardless of copper coverage. there is no variance based on area covered when it comes to tin foil.

if the varying resistance is caused by varied area coverage, wouldn't that be the case with any material, not just the black squares that came with the machine?

also - you're very right about the pad not being triggered when in direct contact of the black square. it's only when pressure is applied (even just a little) that a contact is made.

oh, before i forget. check my LED post in the off topic section since you know your electronics.

Antonym wrote:if this was the case, tell me what you make of this.

any tiny scrap of tin foil that makes even the slightest connection between the two copper coils of the sensor triggers a 127 velocity note, regardless of copper coverage. there is no variance based on area covered when it comes to tin foil.

if the varying resistance is caused by varied area coverage, wouldn't that be the case with any material, not just the black squares that came with the machine?

also - you're very right about the pad not being triggered when in direct contact of the black square. it's only when pressure is applied (even just a little) that a contact is made.

i think that 'The Tinfoil Effect' (sounds like a film with ashton kutcher!) is more down to the much lower resistance of aluminium rather than any varying resistance of the 'graphite'. i'm sure the 'graphite' has a higher resistance than a metal (perhaps your semiconductor suggestion is on point) and it's this that enables the dynamic range of pad hits.

hm. this is interesting and i guess we will find out. either way, this velostat stuff should work. meanwhile i'll work on trying to get a multimeter to read this stuff.

it would be great if it were the varying resistance stuff, because then you could design a pcb to bolt straight onto the metal support, and then just use one sheet of sticky vinyl to stick the pads to that. you'd just need to make sure the unpressured resistance was high enough to not cause erroneous hits.

this is a great thread by the way, just goes to show that the 1k is the thinking man's mpc!

it's been making me think about a lot of things, for sure.

i'm looking to design a midi instrument after i'm done with this experiment.

the midi instrument would take a lot more research but i bet i could do it. the goal would be to control the first 10 midi notes of the scale--by the fingers and thumbs.

this would be done using at first a similar sensor type to what we have in the 1k, but later, with FSRs of the interlink type.

check your pm.

nym youre doin a good job i think but it would be even better if every step was visualized with a picture. my english isn't bad but step by step pictures would be more convenient if this is possible.

Antonym wrote:it's been making me think about a lot of things, for sure.

i'm looking to design a midi instrument after i'm done with this experiment.

the midi instrument would take a lot more research but i bet i could do it. the goal would be to control the first 10 midi notes of the scale--by the fingers and thumbs.

this would be done using at first a similar sensor type to what we have in the 1k, but later, with FSRs of the interlink type.

look into the zendrum i think this is the best "small" midi instrument on the market for drums. but its too bad they only sell it online as far as i know and its 2 expensive to take the guess.

Chulukinat wrote:nym youre doin a good job i think but it would be even better if every step was visualized with a picture. my english isn't bad but step by step pictures would be more convenient if this is possible.

i believe the design is still being finalised, so, it'd be useless showing people how not to do it! i think he's going to wait till he has a design that works well, then document it with pics.

there will be pictures and a little video when i'm done. and for those who don't want to do it themselves, i'll sell it for as cheap as i can without being a nonprofit organization.

i cant believe its come down to tinfoil.....lmao and my conversation on the beat was jus a joke

haha yeah when i realized it was you i figured it was a joke

tin foil is temporary - worst comes to worst, the mpc1000 pads will never be completely broken if you can afford tin foil and tape!

have you read everything else? have you gotten rid of your 1k? if not, keep it.

modnar - i've come to think you're right about the velocity being triggered by area instead of variably conductive material. thanks, wikipedia.

http://www.sensorwiki.org/index.php/For ... istor_(FSR)

look at the diagram - it's almost verbatem what we have going on.

When external force is applied to the sensor, the resistive element is deformed against the substrate....the conductive material on the substrate comes into contact with parts of the active area. The more of the active area that touches the conductive element, the lower the resistance. All FSRs exhibit a "switchlike response", meaning some amount of force is necessary to break the sensor's resistance at rest (approximately 1 MΩ), and push it into the measurement range (beginning at approximately 100 KΩ) (Interlink Electronics 2005).