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Optical Buttons?
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RayB:

--- Quote ---If you haven't built optical buttons then I seriously doubt your ability to judge their practical characteristics.

--- End quote ---

That wasn't really a fair response, given that your original intent was coming up with a noise-free solution. He was correct in saying that you'd get the same amount of noise from the button plastics and spring.


But anyways, on to what I really had to say regarding "analog" buttons:
There is a company that manufactures a "circuit" where the harder you push on the contact point, the resistance changes. I saw a sample of this back in '94 when I was working at a game company. Anyways, the "circuit" was really flat, so I guess they designed it to be stamped onto circuit boards.

The point I'm getting at is this would probably be a better solution than optical, since measuring the resistance would directly relate how hard a button is being pushed. (Unless you're more interested in how FAR it's pushed--more like a throttle?)

I THINK Sony PS2 controllers use the circuit I described above...

HEY I found it! Here it is: http://www.tekscan.com/flexiforce/flexiforce.html
NoOne=NBA=:
I've actually tried to quiet microswitch buttons using a variety of damping materials inside the button itself.
I used cotton, foam, etc... inside the button, and it did help to some extent, but also created more resistance from the damping material pressing against the internal parts on the button.
In the end I determined that the lower noise was not worth the added resistance.

As far as reliability goes on leaf-switches, consider that almost ALL arcade machines prior to the late 80's used them--in arcade environments.
There isn't a much more demanding situation I can think of than the fire button on an Asteroids machine in the early 80's.
I played the SAME machine in a grocery store near school for FOUR years, and they never had a tech out to fix it.
This was not an arcade machine with a tech on site to fix it, and got hammered for at least 8 hours EVERY day.

-----------------------------------------------------

RayB,

You've got much more manly fingers than I do.
I don't want to push ANY button repeatedly in the 5-15 lb. range.
tetsujin:

--- Quote from: RayB on February 01, 2005, 11:12:45 am ---
--- Quote ---If you haven't built optical buttons then I seriously doubt your ability to judge their practical characteristics.

--- End quote ---

That wasn't really a fair response, given that your original intent was coming up with a noise-free solution.

--- End quote ---

It absolutely was.  My concern with noise was in relation to microswitches, where the switch itself is a significant source of noise.  stevejt also implied that optical would be more failure-prone than leaf switches.  Which is possible, given that it's a more complicated solution.  But it'd also be mostly solid-state, whereas leaf switches contain moving parts that need to make electrical contact.  The real answer to optical buttons' reliability is to be determined through testing, unless someone who's built or bought one is going to tell me not to bother...

Mostly, though, I just take exception to responses of the form "you shouldn't try that".  It's entirely possible that he's right, that there will be no practical advantage whatsoever to an optical button, but telling me there's no point in trying this doesn't help me to get it done, you know?  And what if he's wrong?  What if I listened to him when he told me not to bother trying it?  Then I'd never know.


NBA: I have played games in the local arcade which had some dead-buttons.  Whether they were microswitch or leaf, and why they failed, I can't say.  Whether they would have done better or worse with optical buttons, I also can't say.
NoOne=NBA=:
The best optical vs. leafswitch comparison I know of is Tron vs. Gorf.
They used the same joystick TOP, but different bases.

Tron used leafswitches, very similar to the Pac sticks.
Both of them held up very well in arcade environments.

Gorf used an optical approach, and had two sliding "cards" on the bottom that interrupted optical sensors to determine stick direction.

Both of these approaches worked well in practice.

-------------------------------------------------------------------

My comment about button failure was not that it doesn't happen, but that it is not the widespread epidemic that everyone tries to make it out to be.
Buttons DO fail, but they don't go out left-and-right on a daily basis.
Given that alot of arcade machines saw more use in a year than most home machines will see in their lifetime, button failure is not that big a deal.

On a personal note, I've had a few microswitches fail on me in my cabinet, due to the mechanisms getting sticky INSIDE the switch.
A couple were bad straight out of the box.
When this happens, there's not much you can do, but throw them away and get new ones.

By contrast, I've NEVER had a leafswitch fail--even the ones that are 20 years old.
it's just really hard for a leafswitch to flat-out fail.
There are moving parts, but the simplicity of those parts is such that, unless you WEAR them out, they will keep working.

It's two pieces of metal.
As long as those two pieces can create/break contact, they work.
You may need to clean the contacts for optimal performance.
You may need to adjust them to lessen button travel.
But all-in-all there isn't really anything there to BREAK.
Even when the contacts get worn down to nothing, the leafs themselves will continue to open/close the circuit--albeit not as reliably as the contacts.
u_rebelscum:

--- Quote from: tetsujin on January 31, 2005, 03:19:00 pm ---I'm planning to use translucent leaf-type buttons so I can light them...

Has anybody tried building optical pushbuttons?  Or are there any manufactured?

--- End quote ---

One big thing you'll have to be careful is not to mix the button lighting with the optical emitter light.

You can get optical sensor/emitter combos for ~ $1 at newark.com or mouser.com with 0.5 mm movement (horizontal) from min to max sensor lighting.  Most PC mice have even a smaller gap (have you seen how fine the teeth are on some of those mice's encode wheels?), but don't have the shielding like the ones ref'ed above.

A good thing to do is to pass the output through a transistor so the "open"/"closed" boarder is sharper (assuming you want normal digital buttons).  A resistor to adjust the exact open/closed point (for smaller than 0.5 mm, otherwise you need to move the sensor), and maybe a cap to help stop bounce (although most BYOAC keyboard encoders cover bounce).  Take a look at an Atari, Wico, or Betson TB circuit boards for ideas how to wire (but not the new red happs boards or even the slightly older green, as they are much more complicated).

An optical button isn't that hard to make.  I'm not that picky about buttons, however, so I'm not the one to ask "which is better" opinions about button switches.


FWIW, digital Halls Effect switches (yes, digital, not analog) run about the same or a little cheaper than the optical sensors, but minus a magnet.

As far as mame cares, it does not matter if the button switch is leaf, micro, hall effect, optical, piezoresistive, POT, or whatever.  The easiest and most used in the arcades are the leaf and microswitches.  You'll see a lot more optical, hall effect, and piezoresistive in industrial areas (but the piezoresistive is fairly widely used in gamepads). 
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