large scale buttons

[yaiy]

hi all

i am building a midi carpet based on the mios platform.

i have a peace of clothe sandwiched between to pieces of PVC. on the bottom PVC there are 90 large 20x20 cm positive charged buttons. on the other side theres a negatively charged one big piece of aluminum foil.

the carpet size is 2x3 meters.

heres a pic

the piece of cloth is a kind of resistor, only when you stand on the mat the button closes.

my problem is i only built a small scale version of this, one meter in size.

i was wondering if building it full scale will the large foil of aluminum would offer to much resistance.

i hope I'm making sense.

i guess what I'm basically asking is,

can i use the same ground source for all the buttons at the same time?

how can a measure a Resistance of a substance to know if it is too much?

i first used buttons like the ones used in ddr diy kits, basically two slabs of metal with window insulator in between which is used as a spring. its mechanical and so it simply works great,  clean signal. but its to heavy and expensive at large qt. you can see on on the left of the pic.

the new system is portable and (hopefully) it will work but the signal is pretty noisy.

i think i need some kind of gate or process the signal again at the processor. (false positive and false negative are rare but they happen)

thank you for any input

yair

[TK.]

Hi Yair,

I've absolutely no experiences with such a material, but the idea sounds exciting.

Yes, you can use the same ground.

The noise can be filtered by using a "schmitt trigger" before the DIN input - a description can be found here: http://www.play-hookey.com/digital/experiments/rtl_schmitt.html

I would suggest the use of an integrated circuit - eg. the 7414, which provides 6 schmitt triggers in a single chip: http://www.nullohm.de/datenblaetter/index.htm

Best Regards, Thorsten.

[yaiy]

thank you for the replay.

i thought about using that windows osscilator to test the signal.

but i cant figure it out completly.

i orignaly planed on using analog inputs for the midi and cleaning the signal after using the host program.

ill check that "schmitt trigger"