From: bcasper@eos.ncsu.edu (Brian Casper)
Subject: Re: What are Solid State Flippers
Originator: bcasper@c00100-100lez.eos.ncsu.edu
Reply-To: bcasper@eos.ncsu.edu
Organization: North Carolina State University
Date: Thu, 1 Oct 1992 16:19:59 GMT


wwg2101@venus.tamu.edu (GILPIN, W.W.) writes:
|>Solid State flippers are supposed to hit harder or softer depending on how
|>hard the player taps the flipper button. Data East tried this for a while. I 
|>don't think they're doing it anymore. They had reliability problems and also
|>were inconsistent (my nature). I hate 'em cause even if I time a shot perfectly
|>I also have to hit the button with a certain amount of force to get the ball
|>to go where I want it to.

Not exactly...  To understand the need for a SS flipper, let me first explain
for the millionth time how a regular flipper works.

There are two seperate windings in a flipper coil which are wound side by side.
One uses a relatively larger gauge wire and relatively fewer turns, and the
other uses smaller guage wire and more turns.  The two coils are wired in
series and main power to the flipper is supplied from the large transformer
through a relay controlled by the CPU, through the cabinet flipper buttons,
then in to the small coil.  The circuit is completed from the transformer to
the large coil.  The relay is used to turn the flippers on/off during
play/attract modes.  A normally closed switch is located on the flipper
mechanism such that it is opended when the flipper is in the up position.
This end of stroke switch shorts the small wire coil when the flipper is down
so that all of the current will flow through the large portion of the coil and
produce a field strong enough to raise the flipper to the up position.  The
downside to this is that the stronger coil produces a lot of heat - especially
if the player traps the ball by holding the flipper button in for a while.
Once in the up position, the amount of magnetic 'strength' required to hold it
there is comparatively less.  So, to cut the feild strength and the heat, the
eos switch opens and allows current to flow through the smaller coil as well.
The two coils combined maintain the flipper in teh up position until the
flipper button is released.  Once it drops to the lower position, the eos
switch closes again and the process repeats.
  
The eos switch is the weak link in this setup.  Since there is a lot of current
flowing through it, the contacts arc a lot and tend to get pitted and dirty
very quickly.  Better yet, since the flipper crank is always whacking into
one of the blades of the eos, it can crack off.  Now, if the eos isn't making
a good connection, the flipper will be weak because the current is not flowing
entirely through the larger gauge wire in the coil.

Another problem that can cause weak flippers is if the cabinet switches are
pitted and dirty.  Since they carry the same current as the eos switch
contacts, this frequently happens.  All of these problems means more service
calls and less profit for the operator.

The idea behind the SS flipper is to replace this two part coil/eos switch
setup with a timer, and at the same time get rid of the high current cabinet
switches by letting the CPU, or a daughter board and some transistors do the
work.  First, the cabinet switch voltage is dropped to a logic level rather
than 40+ Volts.  As far as the CPU is concerned, it's just another switch
closure like any on the playfield.  Next, the coil is wound using only the
larger gauge wire, and the eos switch is removed altogether.  Now, when the
flipper switch is pressed, a circuit is activated which gives full power to
the coil for a second, then cuts back to about 40% (I think...) for holding in
the up position.

Theoretically, it's a much better setup.  I always thought that the slop
provided by dirty switches slowed the regular flippers down to a manageable
level and that's why they seemed to have better 'feel'.  SS flippers are just
too damn strong and they tend to beat themselves up more quickly.  So either
way, they need service calls.

Although the technology for velocity sensitive switches has been around in
audio keyboards for years, nobody in the pinball arena has tried using them
yet.  I wonder how well a high speed servo and a velo sense key combo might
work...

Sorry to have gotten so long winded, but I tend to do that ;-)
-- 
-- 
Brian Casper                |   "I like to study psychologists.  It gives
bcasper@eos.ncsu.edu        |    good insight into what rats are thinking."
  Pinball Consultant        |     -  Dr. Oscar Wesler