Membrane Swtiches

[Digineural]

I opened up a PC keyboard to use a case and found about 100 or so individual membrane switch domes.  They have a condusive carbon/rubber pad underneath.  Luckily my job is getting rid of about 10 of these types keyboards.  Each keyboard has 100+ domes, so if anybody want to try these out, let me know, I have plenty to go around.  They're also getting rid of 20 or 30 working PSUs from machines no longer under lease. 

I'll try to get a picture of all them up.  The domes about 1/4" high by 3/4"inch in diameter ... roughly.

Let me know if your interested.

Dan

[Jidis]

Dan,

What exactly are those PSU's. Somehow I've always got a shortage of spare working ATX's here. :'(

If they are ATX, what are the average wattages and generation of machines they were pulled from, and are they regular pinning or any of that weird Dell or Compaq stuff that used to be around?

Much much thanks, and PM me if you like, I'll keep an eye out.

George (in VA, USA) 

[Jidis]

PS- On the keys,

Do you or anyone here know if it's possible to etch or otherwise construct the sort of pathways used under those type of switches, in case you wanted a "custom" matrix layout?

I've run across a few myself, and couldn't help but wonder. I've got plenty of regular two-pin momentary equipped keyboards anyway.

Thanks!

George

[Digineural]

A common method to  create a membrane switch board is to use an interlocking pattern like E-C

For example

      +===

      |  ===+

===+==    |======

      |  ===+

      +===

When the carbon pad hits the E and reverse C, the circuit is closed.

Good Luck,

Dan

(BTW, if anyone is willing to design a membrane SEQ panel, I'll pitch in part of the PCB cost and all the membrane switches)

[Jidis]

Dan,

Thanks Again :)

I was mainly wondering more about the actual surface and conductivity requirements of that stuff. It seems like the board's surfaces are always something a bit less "DIY friendly" than regular etched copper traces.

Take Care,

George 

[el-bee]

You could always coat the board and/or button contact surface with some graphite spray. I've used that (namely Kontakt Chemie's Graphit 33) for fixing old console controllers, works fantastically. You need to make a custom spraying mask or tape/cover the areas where graphite isn't wanted though..