Pinball machine - switch closure timing problem

<<Conversely if a switch closure lasts longer than the scan duration it

will be read twice - if it is an intermittent contact, this may
register
as two hits, perhaps this is what is meant by "ghosted" - hard to say
really, without knowing exactly what the software does. >>

All solid state pinball switches are of the type where if held closed,
will not cause a 'multiple scoring', they will simple score once. Some
might keep telling the machine to keep trying to kick a ball out of a
hole etc. but this one I'm dealing with is just a one-shot target so
not an issue.
I understand the concept of the cap and the resistor being across the
switch, it's the values desired I am totally in the dark about. Maybe
just comes down to experimentation. But I also don't want to risk
damaging anything by using too big a cap or too small a resistor etc.
All I have to go by is the manufacturers using a .05 cap by itself on
certain switches...Frenchy
 
It seems that by 'ghosting', it is meant for example that if a diode on
one switch in a switch matrix fails, it can cause false closures on
other switches in the same row and/or column. But this is due to a
shorted part. Not sure why using a cap over a switch could or would
cause this to occur also. Might depend on using too big of a cap, too
small of a cap, if cap was polarized or not etc. Ohhhh I don't know, I
fix pinballs, all I know about electronics is how to put batteries in a
flashlight, that's why I'm buggin you guys! ; )

Frenchy
 
frenchy wrote:
It seems that by 'ghosting', it is meant for example that if a diode on
one switch in a switch matrix fails, it can cause false closures on
other switches in the same row and/or column. But this is due to a
shorted part. Not sure why using a cap over a switch could or would
cause this to occur also. Might depend on using too big of a cap, too
small of a cap, if cap was polarized or not etc. Ohhhh I don't know, I
fix pinballs, all I know about electronics is how to put batteries in a
flashlight, that's why I'm buggin you guys! ; )

Frenchy
Click to expand...
If you use a polarised cap in backwards, it will quite possibly break
(you can think of an electrolytic cap as a really shitty diode with a
lot of capacitance) if you jam enough current up its bum.

If thats what ghosting is, then I doubt it can happen at all with a cap
(unless it craps out).

Cheers
Terry
 
On 23 Mar 2005 07:11:51 -0800, "frenchy" <mf101723@msn.com> wrote:

These are brand new gold-contact switches. No relays, this is solid
state stuff on a new machine. Pretty sure they already have put
debouncing circuitry or software in pinballs for a long time to prevent
false excess scoring etc. Again the basic problem is just sometimes
certain pinball switches don't quite close long enough for the matrix
to pick it up, even if the switch itself is perfect, was done by the
factories for years on certain switches they knew would have this
problem due to a ball really zipping over a rollover switch extremely
fast or a target getting hit hard. In fact the switches in question
work better when softly hit since then the contacts are closed longer.
Hard hits where the contacts are really making even better contact and
with longer stroke due to more movement of the switch, but the total
time of switch closure is shorter due to the speed and rebound off the
switch. Particular swtich in question is same thing, works fine on
glancing hits since then it is closed longer than hard slams...Frenchy
Click to expand...
I know what you are trying to say, but with respect, you are not
correct in everything you say.

Tyhe fact that the switch is new and contacts are gold plated makes
not one jot of difference to the fact that when they are operated in
the manner you say is common, ie. 'hard hit', the contacts bounce like
crazy such that the matrix logic cannot detect a legitimate closure.
One of the main factors affecting the degree of bounce during hard
hits is spring tension on the switch contacts. This is exactly the
same phenomena which a poorly adjusted relay exhibits as I inferred.
Using the relay example, when a relay has only one or two springsets
the load on the armature is very light when it is energised. If the
contacts have insufficient tension the armature slams in hard and very
quickly in much the same manner as your swith when hit hard. The
springsets create a large amount of bounce such that they often fail
to activate the circuitry they control. The solution is to increase
the spring tension so that the tendency to bounce is minimised.

Now I would say that if the matrix logic in this pinball machine fails
to detect a legitimate closure due to excessive bounce on this
particular switch - assuming it is correctly adjusted - then the
design of the bounce suppression logic is very poor. If the switch
contacts are properly tensioned then even assuming a short hard hit
they should stay closed for at least 70 - 100mS - even if they bounce
like crazy afterwards - and this would signify a legitimate closure. I
don't know the time slot length in which the matrix must validate a
legitimate closure but it should be somewhere around 100 - 200mS I
would suggest, but you could perhaps verify just what this time period
is.

When it is all boiled down, a pinball machine with mechanical switches
is no marvel of technology, and since the switches are operated by
human beings who have quite long hand/eye co-ordination times in
comparison to what even fairly simple electronics logic can detect,
the task of detecting a valid switch closure is easy to do. Of course
this depends on the type of logic employed and from the problem you
describe it must be totally inadequate if just this one switch causes
such problems.

I would suggest that you try one of the contact bounce suppression
circuits in the links I provided just for this particular switch. If
it doesn't cure the problem I would be very surprised.
 
On Thu, 24 Mar 2005 03:30:21 GMT, Ross Herbert
<rherber1@bigpond.net.au> wrote:

Perhaps I was overly generous in my identification time period and
they should be ammended downward by a factor of 10. ie. 70 - 100mS
becomes 7 - 10mS and 100 - 200mS becomes 10 - 20mS.

On 23 Mar 2005 07:11:51 -0800, "frenchy" <mf101723@msn.com> wrote:


These are brand new gold-contact switches. No relays, this is solid
state stuff on a new machine. Pretty sure they already have put
debouncing circuitry or software in pinballs for a long time to prevent
false excess scoring etc. Again the basic problem is just sometimes
certain pinball switches don't quite close long enough for the matrix
to pick it up, even if the switch itself is perfect, was done by the
factories for years on certain switches they knew would have this
problem due to a ball really zipping over a rollover switch extremely
fast or a target getting hit hard. In fact the switches in question
work better when softly hit since then the contacts are closed longer.
Hard hits where the contacts are really making even better contact and
with longer stroke due to more movement of the switch, but the total
time of switch closure is shorter due to the speed and rebound off the
switch. Particular swtich in question is same thing, works fine on
glancing hits since then it is closed longer than hard slams...Frenchy

I know what you are trying to say, but with respect, you are not
correct in everything you say.

Tyhe fact that the switch is new and contacts are gold plated makes
not one jot of difference to the fact that when they are operated in
the manner you say is common, ie. 'hard hit', the contacts bounce like
crazy such that the matrix logic cannot detect a legitimate closure.
One of the main factors affecting the degree of bounce during hard
hits is spring tension on the switch contacts. This is exactly the
same phenomena which a poorly adjusted relay exhibits as I inferred.
Using the relay example, when a relay has only one or two springsets
the load on the armature is very light when it is energised. If the
contacts have insufficient tension the armature slams in hard and very
quickly in much the same manner as your swith when hit hard. The
springsets create a large amount of bounce such that they often fail
to activate the circuitry they control. The solution is to increase
the spring tension so that the tendency to bounce is minimised.

Now I would say that if the matrix logic in this pinball machine fails
to detect a legitimate closure due to excessive bounce on this
particular switch - assuming it is correctly adjusted - then the
design of the bounce suppression logic is very poor. If the switch
contacts are properly tensioned then even assuming a short hard hit
they should stay closed for at least 70 - 100mS - even if they bounce
like crazy afterwards - and this would signify a legitimate closure. I
don't know the time slot length in which the matrix must validate a
legitimate closure but it should be somewhere around 100 - 200mS I
would suggest, but you could perhaps verify just what this time period
is.

When it is all boiled down, a pinball machine with mechanical switches
is no marvel of technology, and since the switches are operated by
human beings who have quite long hand/eye co-ordination times in
comparison to what even fairly simple electronics logic can detect,
the task of detecting a valid switch closure is easy to do. Of course
this depends on the type of logic employed and from the problem you
describe it must be totally inadequate if just this one switch causes
such problems.

I would suggest that you try one of the contact bounce suppression
circuits in the links I provided just for this particular switch. If
it doesn't cure the problem I would be very surprised.
Click to expand...
 
<<<The fact that the switch is new and contacts are gold plated makes
not one jot of difference to the fact that when they are operated in
the manner you say is common, ie. 'hard hit' Now I would say that if
the matrix logic in this pinball machine fails to detect a legitimate
closure due to excessive bounce on this
particular switch - assuming it is correctly adjusted - then the
design of the bounce suppression logic is very poor>>

You are assuming it is failing to register due to bounce, but I am
pretty sure this is not the case. Pinballs are expressly designed with
debouncing built into the switch detection, and to NOT reject a switch
closure just because it bounces. They will not reject a 'good' switch
closure (i.e. long enough to be detected) simply because it bounces
afterwards, AND they will debounce it so it doesn't score more than
once. The last thing they want in a switch is for it to multiply
scoring just because the contacts are too close and let the player have
a free advantage. And they also do not want the player cheated so they
do not reject a good closure just because it bounced. So I still think
this is a case of closure time only. Sometimes manufacturers even had
to put caps on rollover switches, which have ZERO bounce by design -
they simply closed and opened too quickly to be detected. There may be
a ton of bounce in a slammed target switch that is not registering due
to small closure time, but I don't believe the bounce has anything to
do with it not registering (in a pinball)...Frenchy
 
On 23 Mar 2005 10:01:14 -0800, "frenchy" <mf101723@msn.com> wrote:

Ok I will keep this in mind, there is nothing that will piss a pinball
player off more than something that is supposed to score when you hit
it, and it doesn't. Bugs in the software can be tolerated to a point,
but when it comes down to a target acting like you never even hit it in
the first place, that's another story. (Electromechanical games did
this routinely since they could only do one thing at a time but that
was expected by players...not so with electronic games.) Right now I
have a 4.7 uf cap and a 150 ohm in series across the switch and seems
to be working flawlessly (so far anyway). If this ends up not being
foolproof I may get back to you on how complicated this opto thing
would be. thanks!....Frenchy
Click to expand...
This is how one guy did the opto thing.
http://www.johnsretroarcade.com/hardware_pinball.asp

Perhaps you could contact him for more info.
 
Thanks. Right now I have experimented a bit based on the .05 uf and
22uf/150 ohm setups used by the companies, and settled on using a 4.7
uf electrolytic cap in series with a 150 ohm resistor across the
switch. It is registering 100% now and I have been purposely hammering
at that target every chance I get for two days. I think I'm calling it
done! Thanks everybody for the input...Frenchy
 
In article <gem0e.12297$1S4.1274812@news.xtra.co.nz>, my_name@ieee.org
says...
frenchy wrote:
Ok I will keep this in mind, there is nothing that will piss a pinball
player off more than something that is supposed to score when you hit
it, and it doesn't. Bugs in the software can be tolerated to a point,
but when it comes down to a target acting like you never even hit it in
the first place, that's another story. (Electromechanical games did
this routinely since they could only do one thing at a time but that
was expected by players...not so with electronic games.) Right now I
have a 4.7 uf cap and a 150 ohm in series across the switch and seems
to be working flawlessly (so far anyway). If this ends up not being
foolproof I may get back to you on how complicated this opto thing
would be. thanks!....Frenchy


Hi Frenchy,

I think you are on the right track. Its been 15 years since I had to
repair a pinball.....

The switch matrix gets scanned frequently - guess every 64ms (numbers to
make maths easy). If there are 64 switches, then each switch gets
scanned every 1ms. Just like ADC sampling, the worst-case is a switch
gets hit the instant after the micro looks at it. If such a switch
closure lasts less than the entire scan duration (ie how long it takes
to have another look) it will be missed.

Conversely if a switch closure lasts longer than the scan duration it
will be read twice - if it is an intermittent contact, this may register
as two hits, perhaps this is what is meant by "ghosted" - hard to say
really, without knowing exactly what the software does.

If you place a cap across the switch, then switch closure will discharge
it with a time constant (Rswitch + Rseries + ESR)*Ccap. The peak current
flowing through the switch is Vopen/(Rswitch + Rseries + ESR). Rswitch
ought to be extremely low, but increases as the switch craps out. ESR
may be low, depending on cap type, but it may also be many tens of Ohms.

The switch then opens, and the cap starts to charge up through the
matrix pullup transistors/resistors. These are usually current limited
in some way, giving a not-too-high charging current to the cap.

You want a nice, fast discharge and a slow charge. For fastest
discharge, set Rseries = 0. Beware the peak current through the switch
though, especially for large C. Many electrolytics have high enough ESR
that this alone will protect the switch. Note that smps electrolytics
are (or bloody well ought to be :) selected for extremely low ESR....

To ensure a slow charge, put a series R between the switch/cap assembly
and the matrix, thusly:

The only thing you guys are forgetting is that with a matrixed switch
Click to expand...
the strobe or ground isn't always there. If the switch gets closed when
the strobe is providing ground for another column of switches the
capacitor is going to do squat. The cap MAY stretch a closure because
of the speed of the strobing, but it is not going to act like a switch
on a "normal" switch.

Jim
 
In article <e34541h7tob8tr5dscq41f38ibkcd2tdcs@4ax.com>, rherber1
@bigpond.net.au says...
On 23 Mar 2005 10:01:14 -0800, "frenchy" <mf101723@msn.com> wrote:

Ok I will keep this in mind, there is nothing that will piss a pinball
player off more than something that is supposed to score when you hit
it, and it doesn't. Bugs in the software can be tolerated to a point,
but when it comes down to a target acting like you never even hit it in
the first place, that's another story. (Electromechanical games did
this routinely since they could only do one thing at a time but that
was expected by players...not so with electronic games.) Right now I
have a 4.7 uf cap and a 150 ohm in series across the switch and seems
to be working flawlessly (so far anyway). If this ends up not being
foolproof I may get back to you on how complicated this opto thing
would be. thanks!....Frenchy

This is how one guy did the opto thing.
http://www.johnsretroarcade.com/hardware_pinball.asp

Perhaps you could contact him for more info.

This is NOT what he needs, and you have to keep in mind, most debounce
Click to expand...
techniques are NOT directly attachable to a switch matrix.

Jim
 
On Thu, 24 Mar 2005 18:11:34 -0500, Dana Raymond wrote:

Uhm... Have you cleaned the contacts? Pinball contacts need to be
periodically cleaned with a small file intended for the purpose. Its been a
decade or two since I repaired pinball machines for a living, but surface
wax cleaner and a point cleaning file and tension adjuster were my stock in
trade.

Don't use a file, sandpaper, emery cloth, matchbook cover, or any other
Click to expand...
abrasive to clean switch contacts. There's a tool, called a "contact
burnisher" that has a metal strip, like a piece of shim, with a rough
surface that's rough enough to clean off dirt and oxide, but not to
grind off the contacts themselves.
http://www.google.com/search?q=%22contact+burnisher%22

Cheers!
Rich
 
yes this is a new machine out of the box and a swtich that most owners
have a particular problem with even after it is cleaned and
doublechecked. These gold ones you just clean with a piece of clean
paper or business card, the old silver ones are filed or
burnished...Frenchy
 
So can you explain in more detail why it MAY be stretching the closure
then? Not sure I understand. Say a switch is closed for an instant
right AFTER being scanned, and opened again before it's row is scanned
again. I.e. switch is closed and opened during a period it was not
being scanned. Why is the cap going to help at all? I know caps DO
help somewhat on matrixed switches, just not really sure why now.
thanks
 
On 23 Mar 2005 21:37:01 -0800, "frenchy" <mf101723@msn.com> wrote:

The fact that the switch is new and contacts are gold plated makes
not one jot of difference to the fact that when they are operated in
the manner you say is common, ie. 'hard hit' Now I would say that if
the matrix logic in this pinball machine fails to detect a legitimate
closure due to excessive bounce on this
particular switch - assuming it is correctly adjusted - then the
design of the bounce suppression logic is very poor

You are assuming it is failing to register due to bounce, but I am
pretty sure this is not the case. Pinballs are expressly designed with
debouncing built into the switch detection, and to NOT reject a switch
closure just because it bounces. They will not reject a 'good' switch
closure (i.e. long enough to be detected) simply because it bounces
afterwards, AND they will debounce it so it doesn't score more than
once. The last thing they want in a switch is for it to multiply
scoring just because the contacts are too close and let the player have
a free advantage. And they also do not want the player cheated so they
do not reject a good closure just because it bounced. So I still think
this is a case of closure time only. Sometimes manufacturers even had
to put caps on rollover switches, which have ZERO bounce by design -
they simply closed and opened too quickly to be detected. There may be
a ton of bounce in a slammed target switch that is not registering due
to small closure time, but I don't believe the bounce has anything to
do with it not registering (in a pinball)...Frenchy
Click to expand...
Is it possible that the series diode on this switch could be going
intermittently open cct? Remove it and connect to your DMM diode test
while placing stress on the leads.

Are you aware of this website http://www.marvin3m.com/fix.htm
 
I read in sci.electronics.design that Ross Herbert
<rherber1@bigpond.net.au> wrote (in
<jdh741t2rjk7gpo7l8oar3av99hku3j3tk@4ax.com>) about 'Pinball machine -
switch closure timing problem', on Fri, 25 Mar 2005:

Are you aware of this website http://www.marvin3m.com/fix.htm
Click to expand...
Spit! I thought it might give a cure for pains in the diodes down your
left-hand side. (;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
On Fri, 25 Mar 2005 09:24:40 +0000, John Woodgate
<jmw@jmwa.demon.contraspam.yuk> wrote:

I read in sci.electronics.design that Ross Herbert
rherber1@bigpond.net.au> wrote (in
jdh741t2rjk7gpo7l8oar3av99hku3j3tk@4ax.com>) about 'Pinball machine -
switch closure timing problem', on Fri, 25 Mar 2005:

Are you aware of this website http://www.marvin3m.com/fix.htm

Spit! I thought it might give a cure for pains in the diodes down your
left-hand side. (;-)
Click to expand...

Do you suffer from this painful affliction? :)

Personally, only my knee diodes give me problems.
 
"Ross Herbert" <rherber1@bigpond.net.au> wrote in message
news:1un741l4df4o03stnuopa9eda646evruct@4ax.com...
On Fri, 25 Mar 2005 09:24:40 +0000, John Woodgate
jmw@jmwa.demon.contraspam.yuk> wrote:

I read in sci.electronics.design that Ross Herbert
rherber1@bigpond.net.au> wrote (in
jdh741t2rjk7gpo7l8oar3av99hku3j3tk@4ax.com>) about 'Pinball machine -
switch closure timing problem', on Fri, 25 Mar 2005:

Are you aware of this website http://www.marvin3m.com/fix.htm

Spit! I thought it might give a cure for pains in the diodes down your
left-hand side. (;-)


Do you suffer from this painful affliction? :)

Personally, only my knee diodes give me problems.
Click to expand...
"Huh huh huh! Very good, Will Robinson."
 
"frenchy" <mf101723@msn.com> wrote in message
news:1111773643.996054.144630@z14g2000cwz.googlegroups.com...
diode tested good. As I said, looks like the 4.7 cap and 150 ohm
resistor have made the switch register every hit now. But don't ask me
how I came up with the values - I guessed ? : / ? ..Frenchy
Click to expand...
I'm sure you experimented and found quantifiable evidence that it was the
appropriate value combination.

Cheers.

Ken
 
On Fri, 25 Mar 2005 10:00:44 -0800, frenchy wrote:

diode tested good. As I said, looks like the 4.7 cap and 150 ohm
resistor have made the switch register every hit now. But don't ask me
how I came up with the values - I guessed ? : / ? ..Frenchy
Click to expand...
That is called "Empirical Design". Don't be ashamed of it - that's the
way most people do it, and the rest lie about it, kinda like wanking. ;-)

Cheers!
Rich
 
On Sat, 26 Mar 2005 10:17:03 +1200, Ken Taylor wrote:

"frenchy" <mf101723@msn.com> wrote in message
news:1111773643.996054.144630@z14g2000cwz.googlegroups.com...
diode tested good. As I said, looks like the 4.7 cap and 150 ohm
resistor have made the switch register every hit now. But don't ask me
how I came up with the values - I guessed ? : / ? ..Frenchy


I'm sure you experimented and found quantifiable evidence that it was the
appropriate value combination.
Click to expand...
I think he slapped it in and played the game, and tested different
values until the game worked. To me, 4.7 sounds a little high, but hey,
whatever works!

Cheers!
Rich
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top