Integrating Akai (MPC/MPD)-like pads in Midibox

[Psykhaze]

Hi !
Was wondering if anybody has even tried to deal with MPC-alike pads and sensors from mpcstuff ? (Just to know)
Link to the pad sensor
Link to a generic 4x4 Silicon Pad set
Sure some AINSER8 modules may help to midify that thing with a new core32?
Asked them a technical datasheet for the sensor part to website sales, hope they will answer positively.

Regards,
JK

[Psykhaze]

Look and these ones for backlit versions :
Link to Sensor Sheet With LED openings
Link to 4x4 Silicon pads backlight-OK

The website provides a lot of nice spare components too =)

[latigid on]

Good for DIY, but for the price I would buy a pre-built unit (e.g. MPD218 = $100) and just send the MIDI out. 

[Psykhaze]

ahah , sure :D
As i already have a mdp32 and wanted to change the pad set to another color, i told myself that with the future "old" pad set and a sensor i could make some experiments ^^
 
 

[Psykhaze]

here the Pads controller schematic from MPC2500 SM that could be ok .

[Psykhaze]

From the email discussion with MPCstuff Sales,
For thoses who wants to create all in one huge controllers with MPD-like pads :p .
( Latigid is right, 99USD is the price of a mpd218 , so it's not interesting to midify this if you only want the MPD-pad) 
But should fit for big on all in one designs 
Price for a pad set (silicon 4x4 pads+sensor) for mutiples units :
5 sets  - $85.00 / set
10 sets - $75.00 / set
25 sets - $60.00 / set
Maybe for those interested try to start a bulk order ?
regards,
JK

[latigid on]

If this only includes the silicone and FSR sheets that's still very expensive. If you don't need velocity sensing you could think about using adafruit (e.g. BLM) or Sparkfun (can be WS2812 enabled) pads which are much cheaper.

Something I don't think you've considered yet is the sensor design. You need interleaved PCB traces (ENIG plating is best) to detect different resistances as velocity changes. Unless you can clone the AKAI PCB exactly you'll need lots of trial and error to get it right. Core STM32F4 has 8 ADCs but they're apparently not that good. There's a board called AINSER which runs over SPI (I think) and might do a better job, but transfers are slower. 

If money and time are no problem, go for it of course. But if you want something that works for cheap I'd consider an existing solution e.g. Novation Launchpad Pro (8*8, illuminated, velocity/pressure sensitive) for <$300.

[Hawkeye]

+1, imho just get a cheap second-hand akai mpd and wire via MIDI, just as Andy suggests... I have one (MPD32) as well and it works great, as long as you only use the pads and don't expect MIDI magic from the rest of the thing :-). They also managed to get pressure sensitivity right and you can adjust to your own preferences using pressure curve configuration... You should be able to score one for less than 80€ second hand... and you can always rip it apart and put it in your own enclosure :-) In the end, this is one thing less to build, that is covered by an established manufacturer and you probably can't beat the purchase price (no way when calculating the build hours) when DIYing, so it makes no real sense - best to  concentrate more on the fun stuff to build, that nobody has built before :)

Many greets,
Peter

[Psykhaze]

Ok then , just was wondering about the subject . As i also have a mpd32 , this was kind just a design concept, not something i was thinking going trough.

[Psykhaze]

I think i found the idea for a DIY costless solution for velocity akai like pads!

First part :
I remembered about electronic drums and piezo sensors for velocity detection. I looked some around the forum but did not find any refs for a piezo that could fit.
May someone advice me a mouser ref @Phatline Edit : is This Piezo ok ? (seems u used some piezo for your bongo trigger) 
Second part :
I remembered that few peoples tried about moulding silicon buttons. An example Here
Now with 3D printing you can easily make your moulds made from CAD design . I'll give a draw to this and try a sparkfun-like mould too.

What do you think about this ?
greets,
JK

Edited May 5, 2016 by Psykhaze

[Phatline]

7 hours ago, Psykhaze said:

First part :
I remembered about electronic drums and piezo sensors for velocity detection. I looked some around the forum but did not find any refs for a piezo that could fit.
May someone advice me a mouser ref @Phatline Edit : is This Piezo ok ? (seems u used some piezo for your bongo trigger)

short answer: YesNo maybe...but they are allmost the same i have ordered

i am still in beta state...give me a week or two... maybe i know more then... in the mean time i have a lot of "if" "maybe" "i gues"  it works but not testet on real bongs (only on table...)

i have ordered that: EPZ-27MS44 they are not wired (you have to solder a cable) and have no feedback loop, but they have all-much the same Resistance (400-500Ohm)

when soldering a wire you have to reduce the heat of the soldering iron...with 450°C you burn a hole in the top-metal...300-350°C is ok

but they are very big about 4cm diameter...maybe for a PAD-Solution smaller are a better choise: mouser they are 1cm and used as loudspeaker thery are for high-tone (vs midtone), dont know what that means in the sensoric way, but mine have peak when hit hardest about 5V.

 

your linked piezzo have a feedback-loop - that is sometimes needed when you use it as loudspeaker(the 3rd wire)... but maybe the have use as triggers too? why that?

>>>problem: coupling vibrations from one pad to the other: if you hit the piezzo to hard, vibration goes to the other pad... this is no problem for me, because i use it on bongos...they vibrate also to the other bongos but not that much, so i programmed software side a minimum voltage threshold (software decouple) which also reduce the velocity sensitivy a bit... much more of course when you use it in pads

triggerpads are a other story...and here comes the Feedback loop in the game > maybe wired on a Digital Input, it helps to find out the correct piezzo element > means if you hit piezzo 1, the DIN Pin 1 gets HI, the software now knows - ignore all other Analog Inputs from the other Piezzos for this moment...so you have the full velocity (stroke the pad)... but that is a bit tricky software side, because- what happens if you hit more pads @ once.... like i said a lot of "if"

 

also the hardware decouple... the stand-the-base-the-case should be very heavy (kilos), it should not vibrate when you hit a pad, because every vibration give Piezzo information on all other pads

then the pad, on its backsidein a hole of diameter about the diameter of the piezzo, in it the piezzo.

and between them case and the Pad should be a very good shock absorbing material, which? > dont know? but they should make a good decouple job...and it should not be to loosy because loosy means vibration - and vibration make fail-triggers on the other pads - a internet search for such triggerpads for drummers should bring more information...but thats not my site...i am on bongos there are other problems.

just my 2 cents

Edited May 5, 2016 by Phatline

[Psykhaze]

Hi @Phatline and thanks for the answers.

The piezo linked  and was choosen to fit as possible to the hardware you have choosen in your bongo trigger design. But your size sounds better ^^ as well as akai pads are 30mm wide.
This way we could exchange about hardware design notes and experiments. I was wondering about some piezo , because i am making a mouser order list.

The feedback loop was choosen to give more hardware designs possibles, and you mentionned one =)

Stand base will , as you said, have to be heavy like in reals akai. But about vibration management, i think silicon could really help. In back like in front ^^.

I'll keep you tuned about my expermients in silicon buttons moulding and velocity sensoring with piezo .

good evening, regards,
JK

 

Edited May 6, 2016 by Psykhaze

[ssp]

only just saw this, been a while since i was last here.  weird no one referred you to my thread.  here you go.