not another midi drum question

MIDIbox HUIs
1

hello everyone,

it has been a long time since i posted a message, but making my next midibox was something that i have been thinking most of my time.

i have a different midibox idea (and also a school project sort of thing)

it will be something like making music using everyday-furniture like couches tables stairs and so forth.

( i know some of you will remember the midi-couch thing -http://www.midibox.org/forum/index.php?topic=4901.0- but what i am planning to do is a bit different and more “less-mechanically built” than midi couch.

what i need is something like an e-drum (please dont give me the edrum links,of course i searched it) without the velocity sensitivity info.

a small example for demonstration can be like this,

-the user sits on the couch and that sends a note-on and when stands up sends a note of (without the velocity sensitivity info)

-the user hits different sides of a table with his hands and gets different note_on and note_off messages (again without the velocity info)

i only know that messing with piezos are dangerous, because they are so sensitive. but since i dont need the velocity info,  would-could it be used as only button switches or something??

i mean when the player hits above a certain treshold it will give note on and off messages??

or is there any alternatives that comes to your mind???

one other example can be like this,

you know the beds with stairs that you have to climb on to get into, if there would be a way to hit those stairs with a stick and again get note on and off signals (without velocity)

the reason i dont want to build an edrum.info thing is the amount of inputs. you can only build 22 analog inputs (which are all velocity sensitive ok) but as you have understood from what i have been trying to explain, i need far more than 22 inputs.

so,

if any ideas come to your mind, please, please help me

thanks

onur

2

Ahh why not just use switches mate?

3

hi,

i cannot use switches for all of them for example i am planning on using the stairs of a bunk as a keyboard instrument which will be hit with sticks (for visual matters)

are there any kinds of pressure sensitive like or -i dont know i could only think of piezos- switches

4

Hi,

are there any kinds of pressure sensitive like or -i dont know i could only think of piezos- switches

Once I used for another project “pressure sensors”.

I only have the german link to CONRAD:

http://www2.produktinfo.conrad.com/datenblaetter/175000-199999/182389-an-01-de-Drucksensor_FSR-149NS.pdf

The sensors registrates the pressure between 10g and 10kg and the are changing their resistance.

greets

Doc

5

thanks for the quick answer

from the pdf i am doing some googling now and learned that there was a thing called pressure sensitive analog switch now i am searching for further info

thank you man

6

Maplin in th UK have this stuff called Quantum Tunnelling material available as small pads and as cable, see:

http://snipurl.com/13hix

It goes from virtually open circuit (10E12 Ohms) to a very few Ohms with pressue. They say it’s good for 1,000,000 operations too. I know a version is used in high end perimeter security systems, but it might work for your application. I fancied it for the action in some home made buttons.

If you’re going to ‘sensor’ the stairs, you’d have to try some of the old ‘Slinky’ toys.

Best wishes

Mike

7

hello all

i guess i found the ideal solution for my project

and i will share it as soon as i realize, test a little and take some photos

im sure someone has used it before me its not an invention

but

i cannot tell you how excited i got when i thought about it

its based on pvc conductive paint that we use in our broken resistances in car windows

8

hello

my first attempts on pvc and conductive paint was quite bad

because that conductive paint shit that i bought works as a resistance and thats too bad.

i am thinking of

glueing two piezos looking at each other with a pvc sheet with a hole where the piezos can touch

so that when im not touching, the piezos wont touch each other

when i touch, theyll touch also

by the way ill only be using the metal part of the piezos, -not to confuse anyone i thought i should be telling that-

9

You should seriously check into how op-amps work. Particularly as used in threshold switching applications. In addition, I would highly recommend you look into general data aquisition sensors.

Check over the E-drum schematics carefully. I know you wanted to bypass that whole idea, but you jumped away from it without even knowing what the designer was doing with it. Pay particular attention to the pad input circuits. You could just as easilly use the same input circuit for ANY type of sensor (provided you tune the resistors to match). Velocity data is primarily software based. E-drum would work on exactly the same electronics, with or without velocity data.

Some sensor ideas:

Piezo microphones - attached to opamps work pretty well for any input that creates sound (this is essentially the same thing as a piezo trigger like E-drum. The only difference is that the mic has more sensitivity to MANY forms of input (impact, audible, pressure, vibration), rather than just impact). Imagine that someone doesnt mearly have to sit on the couch, but need to make the couch squeek. Ummm.. how about a midi sex bed! heh…  only makes music when you are.. umm.. ‘making music’  ;)  I call it art!

Strain Gauges - these are small pieces of thin film on which a set of resistive traces are placed. As the film flexes, the resistance changes. If you put this in as part of a Whyne bridge, it is incredibly sensitive. (Ive used them to measure microflex on 3 story tall mining trucks. The twisting is imperceptable to the human eye) So, this would be perfect for items that need to flex over large surfaces. For instance, you can put a postage stamp sized (or smaller) strain gauge on the CORNER of the stair, by the wall. As a person steps on the stair, that corner is going to flex ever so slightly. You will get a good solid trigger if the output from the whyne bridge is fed into an opamp. for more fun, a two axis strain gauge will be able to ‘locate’ where on the step the person put their foot, as the corner of the stair will flex both lengthwise and depth wise in relation to the foot placement!

In the case of a couch or chair, mount it to a part that is relatively stiff i.e. part of the frame, but close to where the cushion attaches. You will get a definate response, without over flexing the gauge and breaking it.

Good ole light sensor - Get the resistive type. It is a lil glass bubble with a piece of plastic inside. On the plastic is a ‘race track’ of wire that is responsive resistively to variations of light. Again, whyne bridge to op amp, and you can tune exactly what level change you want it to trigger on. A wave of the hand.. or a shadow cast on the wall (and thus the sensor) and you have your trigger.

Even thermal sensors could be used as triggers.. perfect for that hightech fart gag. The person sits down, and warms the seat. At a certain threshold, the trigger fires.. when they get up in startled confusion, the sensor cools off and you can play that diarhea squirts sample you always wanted to use.

Point is.. if you take the time to learn a lot more about data aquisition technology, and op-amps in particular, you can make just about anything an input.

Trust me: look at the edrum again. It is only limitied in inputs because of the constraints of the pic. The input circuit itself will be VERY usefull to you.

10

wow

you really opened my mind

thanks

i will look for all

11

ya know, I looked over the input schematic for the eDrum again, and its actually a pretty impressive circuit.

It presents a 0 to 5 volt swing to the analog inputs on the PIC. It clamps the signal to not exceed 5 volts, thus making it ‘friendly’ to digital logic.

So, you could use this directly with any digital input. There will be a switching range (governed by the input chip’s 0 to 1 threshold) that you need to pay a bit of attention too.. so.. in otherwords, a small trigger on a pressure sensor might not trigger the digital input (say the signal is less than 2 volts).

But take a look at P1, P2, etc..  this is essentially a sensativity adjustment. I would guess that in MOST cases, you need mearly build this circuit for each input, and tune Px so that the output swings over 2.5 volts when you trigger it with the minumum expected trigger. This will be rather LOW sensitivity compared to how you would set it on the eDrum.  Thus, any trigger over your minimum setting will swing the opamp high, and output up to 5 volts. Even if you whack the trigger really hard, it will clip off at 5 volts, and not damage your input.

For some types of input, you might need to experiment with the gain settings (R1, R2, and R3 on the first input).  Get the data sheet on the LM324 before you go poking around.

12

hi ,

i found a workaround to do what i want

dont want to always talk about what i did but not show anything,

but i will give a detailed post. right now i can only think about doing it

13

hi there,

i know it has been a long time since my last entry, and you all forgot about my midibox thing

but i wanted to show you my beta stage midibox, i today bought some fancier stuff to make the interface a bit more good looking, but anyways this is how i solved the trigger problems,

used big piezos only for their conductive surfaces and a glove with 3 small piezos on the fingertops for the ground part of digital inputs(buttons)

i would love to share the maxmsp patch/program which i use to connect this babe to ableton ( i still couldnt learn maxmsp to build a midi sequencer/looper as good as ableton live :)) )

also i got very very interested into audiocommander’s kontaktstation that i see it in my dreams:) i will definitely try doing something like that and contact audiocommander and ask for some help:)so thats all for now have a good year

onur

p.s. i am also capable of standing like a normal person, the height of the table made me look like this i guess

14

Cool :slight_smile:

PS The reason you’re standing all bent over like that is the small screen too low and too far away :slight_smile: Screen top should be at eye level and arm’s length…