Single Input Multipad

[jamalpiper]

I was reading here about Yamaha 3 Zone Rides:

http://www.megadrum.info/forums/viewtopic.php?f=3&t=293

My idea, Have a multipad which uses a single TRS Cable.

The multipad would gain its velocity info from several Piezos wired in parallel under film switches.

Is this Possible Dmitri?

It seems the same theory as yamaha cymbal except the 'just piezo' note would need to be disabled.

[dmitri]

It is probably possible to add a couple more zones. The question is: is it really going to be useful?

[jamalpiper]

http://www.youtube.com/watch?v=tJdIP3kR5qA&feature=related

I'm hoping to do something similar like that.

[elrules]

I think there is no need for that as megadrum has soooooooooo many inputs that you can connect a "standard" drumkit and you still have inputs left to connect a multipiezo pad as the one shown in the youtube video

[jamalpiper]

Well I could get a 25+ ft snake to run my mobile multipad with no problem, but my main reasoning for this is to be able to walk around with only a single TRS cable. Seems alot easier, alot cheaper and alot more mobile.

[Ken Forgettable]

Well I could get a 25+ ft snake to run my mobile multipad with no problem, but my main reasoning for this is to be able to walk around with only a single TRS cable. Seems alot easier, alot cheaper and alot more mobile.

Stuff the MegaDrum in the mobile multipad and walk around with only a single USB cable instead.
Try: http://www.usbwholesale.com/active%20repeater%202.0.htm

[jamalpiper]

I suppose that would work as well. Probably the better option.

Though I like the concept of my idea. If there is a way to make mesh heads give a switch signal, one could theoretically run a large amount of pads off a single input. Even if there were a limit of 8 switches per input, That's 120 pads megadrum could support. (Assuming each set of 8 uses a second channel for piezo data, and the hihat/bass inputs are used as normal.) If several sets of 8 shared a piezo channel, it would break past 200.

Just throwing that thought out there. 120 pads Might not be very practical, but it sure would be cool.

[Synthex]

It is probably possible to add a couple more zones. The question is: is it really going to be useful?

I think this is interesting.
It allows you to connect a big pad on a single input, a multi-zone snare !
Have more inputs at lower cost.

[mcalilj]

If there is a way to make mesh heads give a switch signal, one could theoretically run a large amount of pads off a single input.

Would it work if you hooked up a transistor to the main piezo in a pad? Or maybe added an extra piezo to couple with a transistor? See:
http://en.wikipedia.org/wiki/Piezo_switch

I'm guessing the hard part is figuring out what to do in the event these pads are hit simultaneously. You'll need a sophisticated way of setting up the resistors... An example I can think of is like the options in the "chmod" command in linux. It takes advantage of the fact that the numbers 1, 2, and 4 add up to a unique sum for each combination.

If you have, for example:

Multi.png

Total resistance is:
1/R = S1/R1 + S2/R2 + S3/R3, where Sn = 0 for switch n open and 1 for switch n closed. So you can have the following selection table:

Code: Select all

I/V = 1/R              Pads active
-----------          -------------
          1                      1
          2                      2
          3                1 and 2
          4                      3
          5                2 and 3
          6            1, 2, and 3


For each value of I/V, there can only be one combination of pads that will give that resistance. For more than 3 pads, I guess you could work out a similar scheme, but it would get complicated pretty quickly. I'd have to think about that one...

[mcalilj]

Thought about it some more... selecting resistor values will be a little easier if there's no kick drum/pedals in the inputs.. then you only have to consider combinations of 2 resistors (unless of course you have 3 hands ) The series would go something like this:

1/R(n) = 1/R(n-1) + 1/R(n-2) + 1

so, for 8 inputs, resistances would be in the proportion:

1/R(1) = 1
1/R(2) = 2
1/R(3) = 4
1/R(4) = 7
1/R(5) = 12
1/R(6) = 20
1/R(7) = 33
1/R(8) = 54

I'd put the selection table up, but it's kind of long... the idea is for every combination of 2 pads, their parallel resistance is a unique number, i.e. no two pairs result in the same resistance.

For this to work, you'd also have to be able to measure the current on a pin to a minimum precision of 1/100 or so (1/87 to be exact)... I don't know much about microcontrollers... I guess the atmega is capable of this, but it's probably a question for Dmitri.

Another issue, I guess all piezos on every pad would be wired in series? If 2 pads are hit at the same time, it'd be hard to tell how much velocity to assign to each.... I guess just divide the voltage by 2?