I am setting up a project using a Sparkfun WAV trigger to run sounds in an EM Rifle game (Midway Flying Carpet). My original setup used the default “contact closure” trigger program option, which worked great on the bench (not hooked into the machine), but when I then installed into the machine I got phantom triggers in the few circuits I had hooked up. I had more sounds and triggers which I hadn’t yet hooked up, and which were not involved in the phantom/false triggering. The phantom triggers only occurred when the game was active/playing. No problems in game over mode.
I’m new to circuit cards/microprocessors. I am guessing the cabinet of an EM game in action is too noisy with EMI/RFI to try to hook things up that way (via the contact closure trigger to ground option). I tried a simple shield (small steel breadpan over the WAV trigger) but to little/no effect.
The main 2 things I was going to try next were:
instead of using contact closure (trigger to ground), install a new 5VDC power supply and run that through all the triggers circuits using the “Active- 3.3V/5V” program option.
considering also installing the WAV Trigger outside of the cabinet (maybe on top with a steel sheet under it).
I was guessing # 2 may not be necessary. At first I wasn’t sure if the EMI/RFI was inducing false signals in the wires themselves, or actually directly interfering with the WAV Trigger board. But the more I think about it, only the few triggers that I had hooked up to the machine were involved in the phantom noises, so I think that rules out the position of the circuit card being a problem, and instead means those contact closure signals were being induced in the wires to the board. So I’m thinking maybe #1 above may be all I need to do.
But again I’m not experienced with this stuff and am seeking a more knowledgeable opinion. I’d be most interested in thoughts from folks who have done exactly this (WAV Trigger in an EM game like EM pinball or EM rifle arcade). Any thoughts/insight would be most appreciated!
instead of using contact closure (trigger to ground), install a new 5VDC power supply and run that through all the triggers circuits using the “Active- 3.3V/5V” program option.
considering also installing the WAV Trigger outside of the cabinet (maybe on top with a steel sheet under it).
Yes to both. The active high should serve as a somewhat more affirmative trigger criteria.
But it would be nice to find and solve the phantoms and some shielding might help.
Make sure you’re not mixing the AC/DC voltage in the game with the inputs on the WAV trigger, that can cause issues and possibly damage the part. If the game you’re working on is what I think it is, it’s full of relays and solenoids. Those are quite electrically noisy and could cause false triggers. I don’t know that moving the trigger board outside the cabinet would do too much but you can give it a try.
What you really need is electrical isolation between the game and trigger board, that will help the most with false triggers. If you’re able to drive small relays from the game and use the contacts on those relays to talk to the board, that will help a bunch. Another option would be optoisolators, but if you’re new to electronics, that might be more trouble than using relays.
The active 3.3/5 volt option is a good one to try as well.
Yeah it is isolated in the >direct< sense: I am not using the game’s circuites/voltage sources; I am using an entirely new trigger to ground circuit path using all-new wires/switches serving only the soundcard, insulated from the game’s circuits, with no direct “conduction” path from the game’s circuits to the board. I’m guessing the fields involved are strong enough to induce signals in the wires that trigger the “contact closure” option of the board in my setup.
Think I’ll first try changing 1 thing at a time and reassessing how things improve (first 5VDC power supply to feed triggers, next moving the board outside of the game and with a carbon steel enclosure). If worst comes to worst 3rd I will also use a bank of new low power relays like you suggested for each trigger, to get everything >more< isolated from the EM fields inside the game. Thanks for your inputs!
By default, the trigger inputs use the STM32F04 internal pullups to maintain a high voltage when the trigger inputs are left floating, which is how they are when set for contact closure. With long wires, this internal pullup may not be strong enough to prevent induced signals from fooling the processor into thinking that there’s been a transition. It doesn’t take much. Normal function is for an edge triggered start, so any noise that looks at all like a negative going transition will start a sound. Before doing anything else, you might try adding stronger external pullups, say 2K, to the trigger inputs and see if that fixes your issue.
There are actually unpopulated resistors on the board just for this purpose, although you need surface mount parts to use those pads. Refer to the schematics on the product page. Alternatively, you could add resistors pulled up to 3.3V right to your input wires.
So I’m at the point where I need to go all out and use low power relays to isolate both my trigger board and it’s wiring from the noisy EM control cabinet. I’m pretty sure what I want is an old-school electromagnetic solenoid on/off relay. The wires that control the relays will come out of the game cabinet and up to the relays (which I will have shielded on top of the game). The relays will then open/close switches of wiring feeding the wav trigger board. So the board and the wiring it directly uses will be isolated from the 50VAC game cabinet and all of that noise. It will only be subject to the 5VDC solenoids which I could also separate from the board with distance if there is an issue.
>>>Question: I’m guessing I specifically_>don’t<_ want to pick up the newer-fangled relay modules which seem to work on a trigger board themselves, as they would likely experience the same phantom triggers from their control wiring coming out of the game, as the wav trigger card did. I should instead get a classic electromagnetic solenoid relay with no microprocessor board etc… Those fancy multi-relay modules that look like they run on triggers would probably phantom themselves, and wouldn’t help solve my problem at all, right?
Thanks for any advice for this noob!
YellowDog:
What you really need is electrical isolation between the game and trigger board, that will help the most with false triggers. If you’re able to drive small relays from the game and use the contacts on those relays to talk to the board, that will help a bunch.
I’ve tried doing this and it doesn’t seem to have worked for me. My set up is I have an EM pinball machine (that use to have 8 track sound) and to test I have a new switch stacked on top of the credit button AC powered switch with a piece of plastic between the two. I then have two wires running to the back box where I have the WAV trigger mounted going into the two trigger points
I’ve tried regular resistors attached to the switch and I bought surface mount resistors added to the right of the trigger resistors and tried 2.2k up to 10k and still occasionally get phantom triggers.