RE: Spinner Replacement for Omega Race

> I have created a new compact circuit board that can serve as
> a replacement spinner for Omega Race. It has potential to work
> with other games such as Tron (by replacing the original counter
> board and optionally replacing the original spinner).
 
Hey Bill,
 
Nice job-- board looks good! A few things to consider...
 
1) Might work for Sega G-80 stuff too. I honestly don't remember 100% how
they worked... I think it was a four bit counter with a direction bit and
some way to choose to read buttons vs. spinner. I made a little replacement
for original ones way back when, but likely not in the last ten+ years.
 
2) Is the pulse-per-revolution on the encoder proportional to the Omega Race
encoder? (ie, does the ship stay in sync with the amount of rotation of the
knob?)
 
3) I've done a few designs of these over the last few years (the Arcade
Legends 2/Ultimate Arcade 2, Golden Tee Clubhouse Edition, etc.) all using
CPLDs for quadrature decode and other functions, so based on my experience
you might want to stick a 74HC14 on the inputs to the CPLD to clean up the
edges. With good quality optical encoders at slow speeds it's usually OK,
but with older opto setups (tornado spinners, trackballs, etc.) and higher
spin rates there can be edge chatter that'll give you false pulses (or worst
case, invert your count direction!). Also if you wanted to support older
opto boards you might want to borrow the charge pump/input conditioning
circuit from the Centipede schematics... (make it compatible with old 'opto
only' boards without logic level conversion). Even new Happ opto boards for
their trackballs with the comparitors and logic level outputs will chatter
still going straight into a CPLD. (and some places use those to make
spinner assemblies) If you want to stick with that one encoder you have,
probably no big deal.
 
4) A little MCU might be more flexible than the CPLD if you wanted to
support more input/output formats. With a ~12MHz AVR I can read four
channels of quadrature encoders and still have time to do light gun sensing
and other tasks and still get 1000's of times oversampling. Can't outrun it
with the shaft connected to a power drill. ;-) You don't need pullup
resistors either since the AVR has 'em built in and even the smallest AVR
could have multiple programs built in for different input/output formats.
Also allows you to get around input noise issues in software too, so you
save the 'HC14(s)...
 
5) What's the crystal for?
 
-Clay

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Received on Thu Jul 31 17:50:58 2008