http://stockport.hackspace.org.uk/user/files/tiltswitched.png
1 and 2 show how a tilt switch works. Its essentially a can, with a
drop of mercury in it, and two contacts. When the mercury shorts the
two contacts, the circuit is made, and you know its at the set angle.
- shows how you would set up two sensors so that you know the direction
of a tilt. When it is tilted left, the right hand switch will activate,
and vice versa. This can be tuned simply by adjusting the angle the
switches are at.
I’ve seen a couple of boards that use accelerometers to detect nudge,
and think this might be a better way to do it, especially if you already
have a microcontroller lying about for your plunger. We may be able to
make a board using v-usb (ATMega software USB) on an atmega8 in keyboard
mode, so we can completely skip the extra keyboard encoder!
I’ll have a dig around in my bits box, see what i can come up with 
BobOn Fri, 2009-10-09 at 15:40 +0100, Scott Edwards wrote:
Wow thanks guys. I’ll bring my laptop along with the pinball machine
software then. Will try to get some research done into your
suggestions, it will also help when I get round to sorting a full cab
out as I will probably be putting the same pinball controls onto that
too.
As for the mercury switches for tilting, is there some way to rig a
few of these to sense the direction of the nudge? The emulation just
maps nudges to a button so sensing the force of the shove isn’t
important.
Forgive my ignorance, I’ll be doing some proper research in the
meantime 
2009/10/9 Bob Clough parag0n@ivixor.net
For the actual pinball plunger, I've seen a machine that used
a
replacement plunger (which you can get for next to nothing on
ebay)
connected to an optocoupler, an attiny for detecting how long
the
plunger has been pulled back (for release speed), and a relay
for
switching an input on an i-pac or similar interface.
As far as interfaces go, the main problem with using a PC
keyboard's PCB
is that they use a matrix, and therefore you can get 'ghost
keys' when
too many keys are pressed at once (i think the limit is 3 or 4
on a
modern keyboard).
If you want, i can bring along some parts to the next meeting
for us to
prototype one, as i have a bunch of parts i bought years ago
for an
arcade machine that i've still not built, including some
buttons and an
i-pac, and i'm sure i can dig out an optical sensor from
somewhere :D
If someone fancies bringing along a laptop with some pinball
software on
it, we might even be able to have a game or two :D
Bob
On Fri, 2009-10-09 at 06:42 -0700, Tallscreen wrote:
> > Does anybody have any experience building arcade machine
controllers
> > (Paul/Tallscreen has a cabinet if I am not mistaken)?
>
> Yup! :)
>
> > I am hoping to build a full arcade cabinet eventually but
in the
> > meantime I fancy building a Pinball Controller. Should be
fairly
> > simple with just the plunger and a few buttons for the
flippers/
> > nudging etc. (or perhaps even an accelerometer for the
nudging?!)
>
> By nudging, do you mean like a 'tilt'? You can probably use
a cheaper
> mercury switch.
>
> > This is the sort of thing I have in mind
-http://www.nanotechent.com/pinball-wizard.php
>
> The flipper buttons on that look like standard arcade
buttons.
>
> I'm guessing the buttons just emulate a PC keyboard? You can
just hack
> a keyboard apart and wire up the buttons, but you can
sometimes get
> problems with interference (not so much on modern
keyboards), and
> 'ghosting'. A more elegant solution, which is what I did, is
to buy a
> keyboard encoder (http://wiki.arcadecontrols.com/wiki/
> Keyboard_Encoders). I used a (now obsolete) iPac.
>
> Not sure where you'd get a plunger though!
>
> >
