Homebrew Pinball #3, Part 76

Cross posted from the original Pinside thread, this is one of many posts regarding my third homebrew pinball machine, creatively nicknamed 'P3'

Small updates...

Added a bunch of high scores to the attract mode. Besides stuff like a regular leader board, "best spinner rip", "most hands won", etc I also added a 'lowest scores' board for fun, since technically players can do so bad at poker that they end up in the negative. Could be an interesting thing to compete on!

Had another playtester over for a few hours of gameplay. I noticed they weren't really reading some of the mini screens much. Part of that, I think is just because they're generally really weird. It's hard to get used to looking all over the playfield to see what the writing says. But there's a second issue, which is that some screens were just hard to read. Part of this is due to the viewing angle I think. Displays towards the back of the playfield are both farther away and at a more extreme angle, so they lose contrast. Both of those make them harder to read. But the other thing I realized is that my larger rectangular displays were much dimmer than the smaller square displays I was using for the cards themselves. Each of these displays has a BL pin on them, which is supposedly for the backlight, but I was never able to find much documentation about it, so currently I have it disconnected, and the backlight does seem to work. I wondered if maybe the larger displays needed some extra power on that pin or something, so after failing to find any solid info, I gave up and just started sending random signals in to see what happens. It seems like the BL pin is an active low 'disable' pin to turn it off. Not really useful to me. But while trying to find documentation on it, I also saw some places talking about 3.3V vs 5V. Apparently the actual controller chip on these display boards can run off either voltage, and some manufacturers include level shifting chips so either voltage can be used to communicate. But again, I had no documentation for my boards, which I'd sourced from a random shop on ali express from china in bulk. So I figured, only one way to know for sure!, and just hooked one of the displays up to 5V to see if it smoked or not. Luckily it worked fine, AND got brighter! So I had to rewire all my displays get 5V for power instead of 3V :/

Playtesting also revealed a lot of switch issues. My modified small rollover buttons keep getting stuck in a few places, leading to the game going crazy or balls getting stuck, or sometimes just missing switch hits. I'm hopeful that when I get my CNC fixed and cut a new one, I can align these better, but I'm getting really tired of dealing with issues regarding this. Need to come up with a more permanent solution. I've ordered some proximity sensors to play with, and I also have some other ideas regarding the rollover design to play with.

Around the third hour of playtesting, my new thicker acrylic playfield cover started buckling slightly I'm not sure what causes the heat to do this at this point. I left it for like 8 hours plus with the game on, and had no issues, but now after a few hours I'm having issues? My only other thought at this point is that maybe it's the heat of the flipper coils themselves causing the issue. I've noticed that, especially after long games requiring lots of cradling, the lower flipper coils get quite hot and you can smell them sometimes even, despite the EOS being adjusted properly. I think this is due to the capacitor I've added to the power supply to give them more power. I've ordered some high wattage resistors to attempt to wire in series with the hold winding in a way that they'll reduce the strength of the hold circuit (which is already plenty strong) without affecting the power winding. If that doesn't work, then I may have to mount some tiny fans like people are doing on newer games in order to cool them off.

On the subject of heat, I've also gotten some 120mm computer fans to try to get some airflow moving through the whole cabinet. Even if running the electronics minus the flippers isn't enough to affect the playfield, it still does get quite hot in there and I don't like it. I've also realized that my RPi is mounted upside down on my MPU board, which probably isn't helping things. RPi 4s apparently already run hot, and I had installed some aftermarket heat sinks on mine, but a passive heat sink on the CPU doesn't matter that much if it's upside down. So I've designed a new version of the MPU board which will mount above the RPi to fix that. It should also give me enough space to give the RPi a small dedicated cooling fan if needed.

Pintastic New England has announced their next show will be this November, so bringing the game there is my new goal for the machine. I think it's achievable, in some form, but that means it needs to be able to survive a full day of the public playing it without me being around. At a minimum, I need to fix all these ball hangups. That'll mean fixing some switches, tweaking a few areas of the game slightly, and installing plastics and an apron in case of air balls. I also need to get the action button installed on my lockdown bar to get that presentable. If I can get the game bulletproofed, it'd also be really cool to get some cabinet art, but that might be beyond my capabilities right now. Time will tell...

Posted Tuesday, November 16, 2021
at 11:42 AM

Tags: Blog Post, Pinball, Project, P3,

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