None of the buttons in my guns have 4 leads, they aren't arcade guns.
My solution is sure not the best recommend one, but I did it to avoid touching the button boards and wires too much (I have no replacement if I damage them) or messing up with the button themselves. If I chain solder them and one point in the chain breaks or do wrong contact, it will be such a pain to troubleshoot.
I also have grounds for other things than buttons, like solenoid and rumble.
You can see pics of the inside of my guns to understand what I mean:
http://forum.arcadecontrols.com/index.php/topic,161192.0.html
They changed a lot since I took those pics, but you get the global idea.
Yeah we could do a different pcb for each, but like you said, it would be expensive, and not sure if it's worth it
Well i cant really see whats going on behind that hot-snot glue (which you can remove with rubbing alcohol, if need be
)
But the microswitch (the one you call arcade) is super easy to solder several wires onto, as it has got a hole in the lead which you can hook the end of the wire around before soldering... heck even after if you heat the solder up before.
BTW they are easily obtained, they go by the name 1c25, there are other types such as DB1, DB2 & DB3 but they have a different size, just if need be
and the pcb with the red button(s)? should be pretty easy to wire up with a common ground wire aswell.
Here's a couple of pics of my gun, which surely could use some tidying up.
https://drive.google.com/open?id=1-2D4oAQEHhFUM4F9ROmfW6oOpiYpz_iAThough there are 2 wires connected on one pin of the trigger pcb, the rest are daisychained from there. Just as it was from the factory.
Also should you need spare pcb's, provide me with a drawing with measurements and holesizes.
and i'll design a new one for ya
I could even make one that extends rearward which can hold the arduino, mosfet and all the supporting components.
You wouldnt happen to have a scanner and a ruler would you?
Cause if you lay the gun, or even guns on their (in)side next to the ruler and send me the picture i'll design it to work for that gun.
You'd ofcourse have to make sure that it is clean against the glass, so that there's no warping or out of focus places.
and i'll make it so you have several through-holes where you can attach the ground wires
EDIT:
@JayBee, if you wanted to have me take a look at your code, make a user on github and make a private repository for it and share it with me
EDIT2:
I dont think you should have the camera board act as the ground for the solenoid as that could actually deprive the camera of power on activation (read. inrush current)
what you'd ought to have is a beefy capacitor, maybe even a super capacitor to conserve space right next to the mosfet.