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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!
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