Homebrew turbo-fire circuit?

[DarkBubble]

I've decided that since I've got several systems that I want an arcade stick for, my first project is going to be an all-in-one setup.  I've got plenty of spare controllers and plan to pick up some used pads for the systems that I don't have any extras for to use in the project.

For the most part, I'll be using them for fighting games.  I was originally going to either leave out turbo altogether or wire it only for the controllers that had a Set and Clear setup for controlling turbo.  However, when I thought about how that would include only one of my controllers and how many shooters I have on the systems whose controllers have a physical switch for turbo, sometimes for each individual button, I realized that I'd have to take a different approach.  I've got a combo SNES/Genesis board that I could mount in such a way that would allow access to it's row of turbo switches, but it wouldn't be easy and would bloat the overall project.

I tried cracking open a bunch of my pads, all 3rd-party, only to find that they either had used a different chip in them or had the old black epoxy glob over them so that I couldn't get a look at how they did it.  I figured that if I could find some sort of circuit that could pulse the input from the button to the board, it could be used for each board since my switching method between systems would be networking patch cables.

I've been searching today, and I haven't been able to find anything yet.  Does anyone know if there are any simple turbo-fire circuit projects out there?  I'd love to be able to build one that's adjustable in the way that the old NES Advantage was.  Any help would be appreciated.

[Dave_K.]

http://www94.pair.com/jsoper/autofire.html

Disregard the connection stuff at the bottom, its the circuit at the top that you want.  There are other more complicated autofire circuits for arcade cabinets (which key off the composite sync of the monitor), but I think this simple 555 circuit is what you were looking for.

[DarkBubble]

   That's excellent!  Thanks a lot!

It's been nearly ten years since I took electronics, so my knowledge is extremely weak.  Maybe you can help me out.  Could I make the autofire frequency adjustable by simply replacing one of the resistors with a potentiometer, or would it require more alterations to the values of the other resistor and capacitor?

[Dave_K.]

Yes you could add a potentiometer in one or both of the resistors in that diagram.  Sorry can't help you much more than that, as I'm no EE major myself.  I have planned to build this myself, but lack of time. 

[Spaz Monkey]

http://www.syste.ms/guncon/

Same reference but with pictures.

[Dave_K.]

http://www.syste.ms/guncon/

Same reference but with pictures.

Nice!

[DarkBubble]

God I love how helpful this forum is!

If I want independent turbo for individual buttons, is it as easy as making more than one ciruit, making sure to daisy-chain the +5V from pin 4 of the previous chip in line to pin 8 of the next in line, and so on?

Thanks for all your help up to this point, Dave and Spaz!

[Dave_K.]

Simple, just daisy chain the "rapid gnd" wire from the diagram for any button you want to make turbo.

[Spaz Monkey]

I don't know if this is an option for you, but I have a PS controller made by High Frequency.  (Clear plastic with groves for your fingers).  It has a Slow button, Turbo, and Reset.  Hold down whatever button, push Turbo *poof* you got turbo on that button only.  To reset it, hold the button down, push reset.  Maybe find that controller and hack it.  It sounds that you have some soldering skills.

(Sorry, I'm not trading the controller)

[DarkBubble]

I don't know if this is an option for you, but I have a PS controller made by High Frequency.  (Clear plastic with groves for your fingers).  It has a Slow button, Turbo, and Reset.  Hold down whatever button, push Turbo *poof* you got turbo on that button only.  To reset it, hold the button down, push reset.  Maybe find that controller and hack it.  It sounds that you have some soldering skills.

(Sorry, I'm not trading the controller)

That type of turbo scheme's pretty common on 3rd party PS controllers.  I've got a Performance pad, two Mini Shock "arcade" sticks, and a 2-player Blaze arcade-style panel that all operate that way.  While it'd be great if I were planning to only use a PS board, even if just the turbo circuit from one of them could be hacked and adapted for use with multiple boards, I'm pretty sure that I don't have the skills at this time.  Maybe it's something I can look into later, when I'm a bit more confident.  Now that I think about it, I think Blockbuster had a used pad like the one you mentioned, but it was grey.  They're liquidating a bunch of stuff in the Game Rush department at 50% off, and it's $3 before the half off.

Simple, just daisy chain the "rapid gnd" wire from the diagram for any button you want to make turbo.

In that case, rather than using a single switch to turn on the turbo circuit, would I want to use a SPDT for switching a particular button between ground and rapid ground?

[Dave_K.]

In that case, rather than using a single switch to turn on the turbo circuit, would I want to use a SPDT for switching a particular button between ground and rapid ground?

Sounds like a good plan to me!