Wooden Pinball + Arduino DIY (40x40cm mini size) 

Ball lock is using step motor. Forward and backward is well calculated and controls

For parts infomation, please check end of this video.

@@Adam-do3ny thank you for the reply! I have watched your amazing video and I saw that you mentioned 'micro switch', but unfortunately it is too general... There are hunderds of micro switch types. No worries mate, I will find the one I need. Thank you anyway.

There are actually tons of optical sensors used in pinball, especially along steep ramps and tough shots. Looking at 92's Bram Stoker's Dracula, for example, the video mode right orbit uses an optical, the entrance to the loop uses an optical, and mist multiball uses an optical + a laser to determine if the ball was knocked off course. (A magnet is dragged across the field by a motor, the magnet drags the extra ball across the field and you need to knock it loose to claim your multiball). But both of the left loop exits and the coffin loop use mechanical switches . . . why? Far. More. Reliable. But you don't want to place them at the entrance because they might slow down the ball and prevent it from making the full loop. So you only place them on parts where the ball is coming out of the path and falling down. Mech switches are moreorless designed so that a pinball sat right on top of them will always have enough energy to roll over/through them from a sitting position. Optical switches fail whenever there's a bit of steam or condensation, whenever there's wear on the glass plating, (a big reason not to mount them facing up from the whitewood), whenever there's dust that sets off the sensor, whenever the balls are either too dirty or too clean, if the board backing is the exact wrong colour, if a nearby lamp shines into them . . . Backing up a moment, optical switches are really reliable, despite many modes of failure, they're all low probability. They also don't take as much direct wear as mechanical switches . . . but the surfaces around them do. And a pinball machine deals with a 2 ounce ball of metal bouncing around at upto 150 km/h, whacking everything with about 50N of force. And it's going to rollover some switches dozens of times per game. (The inlanes, particularly). And you want this machine to last years without serious maintenance, preferably with lots of people playing it every day if you like profits and money. Fixing a mechanical switch usually just consists of rebending a piece of metal. Or bending a paperclip into the right shape and slotting it in. Fixing an optical switch is usually a complete replacement, but sometimes also necessitating refinishing the playfield near the optical switch, fixing lamp housings, and other problems. Because of the variety of ways an optical switch can fail, and because the failure usually isn't visible, fixing one usually requires a good bit of guesswork. But checking your guesses takes a lot of time, especially for intermittent problems . . . which optical switches also tend towards when they begin failing. So, what does maintenance actually look like in the long term? When restoring a 30-year-old game, it typical involves screwing with about half the mechanical switches, replacing one in full usually and the rest just need some tinkering with. And fully replacing all the optical switches . . . if you can even find suitable replacements. The '92 BSD near to me actually didn't need any of its optical switches replaced, but all three needed new glass in front of them because the damage meant they weren't seeing the ball all the time, and the video ramp one needed a lamp replaced and brightened near it as it became less sensitive with age and wasn't triggering every time, (I think it still undertriggers). The mechanical switches were all also fairly good, only an arm missing from the switch on the (non-secret passage) loop exit, which was easily replaced with a paperclip bent into shape. (I told the operator about the missing switch and got to watch him replace it in front of me :P) . . . except . . . the EOS for board control in that machine also uses optical switches! The left flipper is fine, but the right flipper's EOS only decides to work randomly, which means you can't reliably use it in video mode, to check status report, or for lane switching. The mechanical switch part of the EOS, which is used to switch from inrush to holding current, of course is working or else the solenoid would be burnt out. But you don't plug the high-voltage mech EOS directly into the low-voltage computer! (This is an excellent use for optical switches as well: not mixing two different voltages on nearby switches, thus not even having any wires nearby to mis-connect and blow your control board) TL;DR: Pinball machines do use optical switches, but not for everything Mechanical switches are far easier to repair Mechanical switches have fewer modes of failure and are easier to diagnose Mechanical switches fail less catastrophically over long periods of time and wear. Mechanical switches require less guesswork to fix, which means far less time to fix The downsides of mechanical switches have been designed to a minimum since before optical switches existed

Ya, drill the small hole must be very catefull, haha

No sensor, it use steel ball to contact and short the circuit inside the hole, then use servo to push out.