I am adding a mod to a EM game to track scoring and throw some high intensity LEDs onto the game... using an Arduino..

I guess my question is what exactly are you thinking of doing? Pulling the score reels out and throwing in LCD's? Removing all Coils and switching to AC coils? Just removing all the relays, like the AX/Reset/Etc etc.. and running digital logic on them?

The issue to me is not the AC->DC conversion, you could simple use Opto couplers for the interface and keep the game on AC. I guess I just do not see the vision, what EXACTLY do you want to replace? Cause if your going to replace switch stacks only, which is the "flaky" part of an EM (which is in reality not that flaky) your task is fairly "easy" as the logic is pretty straight forward. If your going to go for the score motor as well... its going to get pretty damn complicated pretty fast. You have a crap ton of timing type issues you would need to code so that bonus counted down correctly (e.g. not faster than the reel could reset or the lights would blink) etc etc.. You might even run into that a little just doing relays-

I personally, have LOTS of interest in Arduino and pinball.... this particular task seems kinda on the less interesting part. The game would be essentially worthless when you were done, who would want it- the code alone would be fairly complex and large and difficult to deal with unless your a code pro who throughly self documents and you sold it to another high level person. The game would likely NOT be more reliable cause there would be a few hundred new wires with little to explain why they were there...

If its a because I want to learn and I think I can do this and it would be cool to me.... kinda thing then

DO IT. Cause you will learn a shit ton-

If you think your going to somehow make a better game- I seriously, seriously doubt it. I would bet large sums of money I do not have that it will be a larger maintenance headache when your done then it is in the condition its in now.

Also- EM's are hardly rare - and its your machine, so I have less worries about one less EM being available. Most are falling apart in place and selling for a few hundred bucks out of a garage.... you modding one is inconsequential. If your dealing with an otherwise unremarkable game. Something rare, with real value should be left alone.

Not to interrupt a ongoing discussion... with an answer to a prior question..

But with regards to my Arduino mod to sense score reel increments and animate some PWM LED's. I have this mod about 80 % done, its in or part of the end of the thread I have here on my efforts to restore the Super Spin (which was accomplished a while ago). Sadly, I have too much going on with my work on restoring a very trashed Bally Playboy PF on going concurrently with the Arduino mod and my real Job. So if your interested in how I did the circuitry and such- thats all finished and I posted detailed schematics and have tested a little bit while running the processor and all seems good.

I decided to basically build a rectifier circuit to deal with the AC voltage on the Pin and then use DC relays so that when the coil fires in the game the AC voltage rectifies to DC, triggers a DC relay which then sends a 5V DC current into a digital pin on the Arduino with a pull down resistor (to ground) being in place on the NC side of the relay. In this way I can "see" the coil fire in real time and use the processor to then run PWM output to three LED colors.

Things I need to test as of yet-
I need to plug this into the game and see if my rectifying circuit is working and the DC relays are actually triggering- this is trivial to fix if I FUBAR myself by over thinking the rectifying--- to that end... I threw in some Zener diodes to scale the voltage to a 24 V DC so as not to push the relay to hard- but if the theoretical rectified voltage is a little lower than the peak I calculated I may need to remove those... no biggie-

Any how, none of what I did really apply at all to your thoughts here.

However, in thinking about your idea, perhaps you could sorta start using something like what I am doing on a larger scale to bring in the coil firing patterns into an Arduino from some or even ALL the coils on your game-

One thing you could do would be to take my circuitry and eliminate the rectifiying circuitry and go with opto couplers (what I could/should have done) this would greatly simplify things, then you could get a big bead board and throw 100 opto couplers down and easily monitor coil firing patterns on the processor. The one limitation I am seeing in writing this, is how the heck are you going to deal with the game requiring as many as 40+ coils independently firing whereas the Arduino is limited to something like 9 outputs (maybe is 12 whatever- it is NOT 40-100). You can certainly use software and some expansion ports to perhaps get close.. but the Raspberry Pi might be better for this- Arduino might get hammered with software computes to bit bang output to 40 or 100 channels while trying to also run the code rule set.. unsure... it might be fine but its not exactly a work horse computationally and its pretty limited for memory.
Anyhow- if you DID build an input bead board set up with opto couplers and managed to interface it to a processor, you could just aligator clip to all the coils in your existing game, and basically see if you can deal with the input and the code to "fake" the output/input required to run the game- without moding the game at all... then once you know whats up its your decision to go forward. But at least you would have some idea of how the hell its all going to work and the challenges- without having destroyed the game in the learning process..

A wikipedia search for opto-isolator will inform you that you can get these with response times in the sub nano second range using a photo diode opto, which is insane compared to the coil times on an EM... so you can likely use a cheaper part like a 4N35 photodiode which they say has a response time of around 5 uS and can handle PWM control circuitry- I think a 4N35 costs about 0.37 dollars from new-egg.... so clearly we are not limited by speed with opto couplers on an EM- not even close..... but you do need to at least look up their speed cause some are in fact quite slow...

I propose to spend your 37 cents, go get one, hook it up, and see if you can see it, just use your Arduino you have laying around and bead board it up, run the 5 V DC out into the switched side and alligator clip the inputs into the game... But do your homework and check how these work, I have not wired one up but its basically a relay so nothing to fancy. Then tell us what you see... you may want to run the input coil voltage through a diode to isolate the reverse EMF from the coil when it shuts down...

Please please- I have not done this, check to see if you need to rectify etc.. just sayin- might need a zenner as well- but even with everything were talking less than 3 bucks to assemble assuming you have a bead board and wire.

Meh... I have my Arduino mod sitting 2/3 complete whilst I waste my free time screwing around with something more interesting (- another pinball project but one thats just eating time currently)- do what's interesting to you-

Have fun with the EM- they are great.

Once I get my ARduino mod done I will PM you with what it looks like just for giggles... perhaps it will incite you to do something stupid like scratch build a new machine! We all need a little push to go over the edge.

No worries on my end, I told him to purchase the equipment and start testing to begin modding away- But he wimped out! Push- Push- Push... come on! Go fer It

Awesome- I love the sense of accomplishment these EM games bring in rebuilding and fixing their myriad of mechanical contraptions. Congrats! You have the fever now...