Buttons double firing -- please help

[ahofle]

Hello,
I have a bunch of happ pushbuttons with horizontal microswitches and a 4 player I-pac in my mame cab.  I seem to have an intermittent problem when pressing buttons occasionally, in that it will register two clicks with one press.  Bringing up notepad and pressing the buttons, several of them occasionally register two characters instead of one.  Is this a common problem?  Any idea where to look?  It makes certain games very difficult to play (not to mention entering my initials in the highscore screen lol).

Thx,
Andy

[cholin]

Im guessing theres probably a short in the wiring connecting some of the NC ports to NO ports so when the button is down, it registers a press and when it goes up, it registers another.  Check your wiring, since that's usually the problem.  Best thing to do always though when you have a problem with Ultimarc is to email andy.

[MonitorGuru]

Are your buttons (well, at least the switches) old?  Are they genuine Cherry switches or some off brand?

My first thought is very dirty contacts/bent connectors inside the switch.   

Do all switches do this? or just a few?  If All, then it is some common wiring problem or a failure in the IPac, because to have that many switches go back is highly unlikely, unless they all came out of 20 year old cabinets.

Is this a USB or PS/2 IPac?  If USB you may have USB driver issues on your machine. If PS/2 are you trying to connect a PS/2 keyboard at the same time? That could cause some problems if done through a Y connector/etc...

If you're certain it's a few switches, don't spend too much time diagnosing as replacement cherry switches are only 90 cents each or so from Bob roberts (and new switches with new buttons are only like $1.45 from him)

[tetsujin]

Interesting.  Could this be an effect of switch bounce?  (Does the I-Pac not de-bounce switch inputs?)


Educational Segment:

For those not familiar with switch bounce, here's what it is.  When a switch is pressed, its two contacts come in contact, allowing current to flow.  But there's some impact there, so a terminal that hits its mating terminal with some force may contact, bounce off, and contact again.  (I imagine this is especially true in microswitches, where the transition from one state to the other is rather fast.)  This can cause a device, over the period of a millisecond or so, to see the button change state several times as it's being pressed.

De-bouncing is the process through which devices counteract this phenomenon, by using a timer to ignore state changes that happen too close together.

[ahofle]

At first, I thought it was only a few buttons, but I will test that theory in great length tonight and report back.  The (cherry) switches and buttons are all less than 2 years old.  The weird thing is it's very intermittent.  I would think if it were wired incorrectly, it would fail every press.  But it's more like every 10 presses or so.  Good idea about emailing Andy...I'll do that now too.  Just wondering if this was a FAQ.
Thx all for the input!

[MonitorGuru]

The way microswitches are made, it's' very hard to get bounce. A lot easier on a leaf switch.

A microswitch includes a curved piece of metal. Once it is pressed enough, the metal QUICKLY and securely snaps to the opposite terminal (usually) providing almost zero bounce and always BREAK before MAKE functionality.

The only thing that would give bounce would be very dirty contacts inside (e.g. ones that are simply old, or ones that have succumed to oxidation through sweat/oil falling in them from a bad control panel/button or other humididty changes)

To control bounce, you can put very small ceramic disc capacitors on the line.

[ShinAce]

Yep, sounds like an old switch that soon needs replacing.

[tommy]

Do you have a few buttons wired to one microswitch , sounds like a ground oroblem.

[redcoats]

This actaully sounds like the buttons are hooked up wrong? There should be three prongs on the microswitches. Ground goes on the further back prong and the power goes to the middle if it is not hooked up this way it will be like auto fire. If you do have them hooked up correctly I have no idea what the problem is?

[cdbrown]

I had this problem on one of my buttons.  Push it in slightly and it would register the press, keep pushing in further and it wouldn't register anymore.  I opened up notepad to test all my buttons - all but one would register the corresponding letter once when pressed quickly, if help down all but one would repeat the corresponding letter.  Replaced the faulty microswitch and everything works.

[ahofle]

Update.
It seems that about half of my buttons (around 10 or so) have this problem.

[ShinAce]

Until you replace one of the microswitches and retest, stop making foolish assumptions.
Two years of heavy use should show AT LEAST one failure. Look at the joystick switches, and you'll see one is clearly more worn that the others. From experience, I can tell you that's likely the switch for down. If that cherry actuator on it shows enough wear to expose the white, that's a clue to keep a close eye on all switches.

[Lilwolf]

but having 10 fail? 

I'm guessing its either a single wire on the grounds or something with the ipac.

But since you have soldered the wires... you can't easily check that... so try this...   Reprogram the ipac (since its easy).  Then try swapping a button that is working with one that isnt (at the ipac... two screws and your done).  Does the problem follow the button?  If not the ipac might have some issues...

Ok, now we know its the wiring.  Do you have the 10 buttons on the same ground (and the others on another one?)  Then you probably just want to redo the ground wire end to end. 

You can also write a quick program that detects key presses / releases and sends them to the console.  Then force a button down (either by hand or with a wire) and then start shaking each ground wire.  See if you can make it fault. 

Good luck

[rdagger]

Your picture of the buttons shows a brownish discoloration where the ground terminals meet the plastic base of the switch.  There's a possibility that you heated the microswitches too much when you soldered them and shortened their life.

[Flinkly]

if you do end up witching them, invest in some quick disconnects...

[ahofle]

OK I'm ordering a bunch of new microswitches from therealbobroberts.com.

[cholin]

Solderring is frowned upon because if you order some Quick Disconnects for $6, you have better contact and it's easier to remove.  Basically, its the idea that you don't have to take apart the whole thing to replace a switch or two, instead, you pull the connect off and slide it onto another switch.  Solderring is fine, but QDs are cheap and reliable.

[ahofle]

Where'd you get them for that cheap?

[cholin]

The quick disconnects?  Peale has a link in his sig and if you look under Connectors, he sells them by the bag of 100.  I plan on buying some when I get some cash in the good ol paypal account

EDIT: Sorry, I said Paige, meant Peale, fixed.

[ahofle]

Well I found a new unused cherry switch in my garage from a 3 player start button I never got around to installing.  I replaced one of the buttons that always 'skipped', installing it with no soldering.  I haven't been able to get it to happen yet in about 100 clicks.  So it looks like it must be that my switches are bad.  10,000,000 click MTF ---my bottom---.    Very odd.  Maybe overheating them with the soldering gun was the catalyst that accelerated their premature failure. 

Thanks for all the help. 

[Apollo]

If it does become a problem the best way to solve it usually to slow down key repeat in windoze.

[paigeoliver]

I don't have quick disconnects, but darn near every auto parts store around sells them in both common arcade sizes (both of which are also common car stereo sizes).

[ShinAce]

Please, if you use disconnects, get the non-insulated ones. That way, you can solder your wire to the disconnect, and get the best possible connection. At that point, your disconnect will have good enough contact with the switch to ensure good operation. But a crimped connection is never 100% reliable.

A switch wears down both electrically and mechanically(related though). You can always open yours and blow out the dust.

I had a friend have hid 'down' go out on a MAS stick. Checked the switch, it was awful, and replaced it. Later that night, I opened it just to see how much wear there was. Welll, it turns out the switch had a dust ball in it. Cleaning it might have let me use it a few more months, but overall, not worth it.

[NoOne=NBA=]

Solderring is frowned upon because if you order some Quick Disconnects for $6, you have better contact

Wrong.

1) Soldering is NOT frowned upon by alot of people around here.

2) A good solder joint is a better connection than disconnects.
Do you suppose there's a reason they don't put all the guts of a radio in with press fittings?

and it's easier to remove.

True, but not THAT much easier, and not a big deal unless you plan to rearrange stuff regularly.

Basically, its the idea that you don't have to take apart the whole thing to replace a switch or two, instead, you pull the connect off and slide it onto another switch.

Nor do you with solder.
You just desolder the switch you are replacing, and solder the new one in.

Solderring is fine, but QDs are cheap and reliable.

Cheap compared to what?
I've got a $3.19 roll of solder sitting here that's done EVERY project I've done (arcade, school, personal, etc...) for the last 15 years, or so.
$6.00 for one or two machines sounds kind of expensive by comparison.

[BackAgain]

I always use a heat sink while soldering.

[tommy]

Solderring is frowned upon because if you order some Quick Disconnects for $6, you have better contact

Wrong.

1) Soldering is NOT frowned upon by alot of people around here.

2) A good solder joint is a better connection than disconnects.
Do you suppose there's a reason they don't put all the guts of a radio in with press fittings?

You dont need to make your microswitch hold up in a hurricane, just as long as the wires are touching it will work, dissconnects are fine , why dont you weld your tire on the hub so theres no chance it will ever fall off, microswitches and radios , apples and oranges.

[ahofle]

Well I did take apart the switch that was bad, and I tell you it's as clean as a whistle in there, with absolutely zero oxidation.  The contacts all look correct when I press the red button.  I just don't get it.  Andy from ultimarc mentioned that American made cherry switches succumb to this problem much more than the European ones.  Anyway I ordered a bunch of replacements.  I also had a friend of mine test out his buttons and he found 4 that exibited this same behavior in notepad.

Thanks again for all the help.