Friday, September 14, 2012

door actuator pin - starting the design

Ok, so I may not have even drilled the first hole in wood, but that's just how I am.  I tend to overplan, but it really does prevent issues from happening during assembly.  It's the measure 10 times cut once mantra that loops in my head.

Anyway, I have enough modeled in solidworks at this point where I could at least get the flippers mounted and wired up.  I started creating an apron troft, even if I don't quite yet have the ball eject worked out (probably going to use another actuator with a lever that flings it up).  I plan on using 1/16" aluminum and getting it lasered from a place like ponoko, as I think it will cost less than waterjet (my local place tends to do more industrial jobs, and usually has a minimal $50 lot charge plus programming)  My goal is to get all the rails to fit within a 12" x 24" piece, which on mcmaster is about $22.

Here are some photos of what I have so far.  I decided to go minimalist (and save precious playfield space) by having the ball eject ASAP.  This has been done on other pins, and it seems to work well:

Since my mechanism doesn't have a base plate, or any specific pinball parts (pawls, flipper bats and bushings are non-specific to any company), it will be cost effective and not infringe on any design patents.  Also the hole on the end of the solenoid should interface with the pawl beautifully.


  1. Looks good so far. I like that you are going electric, but well, I'm an EE, so that's kind of what I'm into. I think that going electric feels more like a pinball machine to me. All the other early versions of pinball with just jostling the cabinet feel more like a ball maze than an actual pinball machine.

    The Williams type ball ejector idea might work well with your design. If you make the race from the ball drain position to the shooter slowly rise in height until you get to the shooter (basically use it as metal rails), it might allow you to use a simple solenoid to kick the ball up the hill and put a ball in play.

    If you want help on the door actuator driver, send me the part num (need specs for voltage and current), and I can probably make you a driver from the spare parts that I have lying around. (I'm also working on the AC to 50 VDC bridge converter design which might be useful to you. I just need to toss on the voltage regulators and test it, but once that is done, I have 4 extras of those boards, and I'd gladly give you one of them. You just have to get/solder the parts on yourself) I'm using 3 TL783's in parallel to drop the voltage and I'm not sure it will handle the current gracefully.

    Looks like you are making good progress. I'm enjoying the Craigslist blog. So many things are true with people believing that they have a $2000 1975 pinball machine. Have you guys been watching Pawn Stars too much? Look in the back corner, the machine is still sitting there, so evidently it wasn't worth that much.

    Black Knight was one of my favorites from back in the day. (They had it at the local roller rink). One bummer about it was it could be a real drain monster. Played one down in Allentown this year, and it was in such poor shape, it wasn't worth the time. One of those machines in tip top shape is a lot of fun. How many machines do you have at this point?

  2. Yea, I still might want to do an all mechanical at some point (perhaps hand crafted by amish people I know), but I think a 12v system is still minimalism. Yea I'm not sure if my ejector will really work or not, I think it needs a bit more than just walls (unless I go only one ball at a time).

    To power the door actuator, I'm just going to wire it directly into a cherry switch, which seemed to work good in my early test:

    I don't know if it's pawn stars, or ebay, but people ARE getting the wrong idea of what things are valued at. American Pickers doesn't help either, and it's the same thing (oh look, there's that Ali pinball you bought 2 seasons ago for $600).

    I've only played black knight in person maybe once before it broke (never had one in arcades growing up, but played the hell out of bk2k). Been loving playing it on future pinball and pinball arcade, so I decided to find one. Found one 4 hours away in indiana for $750 in sad shape (dirty, coin mechanism jammed with 9 quarters, flippers barely hanging on, ball ejector solenoid hanging from the playfield). I'm touching up the outside cabinet first, then diving in.

    I own 5 pins now, I'm on pinside:

  3. Looks like you are also getting more into fixing the electronics in the machines. Nothing better than being able to fix all of that stuff yourself. If you can do that, you can pick up a lot of good machines that others won't touch because the electronics are in bad shape. (The old Williams mantra of if the board doesn't work swap it out, makes for an expensive proposition for somebody who isn't running 20 or 30 machines and doesn't have any spare tested parts lying around.) Sure you could toss a new MPU board in the machine for $300, but that's a pretty expensive proposition.

    Nice collection of machines. None of the things you mention on BK are too worrisome. As long as the playfield is nice, and there is only a little to no battery acid damage, everything else will work out fine. (ooh, except broken displays...those can get expensive) Even the battery acid stuff can be worked out usually if you spend the time.

    A power door actuator is usually just a solenoid in a different case. Can be either AC or DC, but usually for cars it is 12 VDC. You should still consider tossing a diode across it to protect your battery/power supply. Otherwise you can get a nasty voltage spike.

    Keep plugging away. I got a chance to work on the main controller code for the open pinball project stuff this week. (Basically the MPU for the project). I made a little mistake in using the MCF52212 processor, and not noticing that it didn't have enough memory for running the USB CDC stack and the RTOS. It took me a couple days, but now takes less than half the resources (RAM and Flash) of the processor. Full steam ahead.

  4. From what I know, a power door actuator is usually a solenoid in different clothes. They can be either AC or DC, but if you grabbed it from an old car, it will be DC. It cracks me up looking at the video. Don't know if you ever played it, but Atari put out a machine called Hercules. I think it had the same size ball as the tennis ball you were using in your flipper test. When you switch from using a battery to using a power supply, you should consider a diode across the actuator. Otherwise you will get a nasty voltage spike which may or may not hurt things.

    The things that I fear at this point are nasty worn playfields, peeling painted backglasses, and smoked displays. Most small amounts of acid damage can be fixed as long as it hasn't completely corroded off the pads. The black knight machine looks in really good shape in those aspects.

    Running a pinball off 12V would be spectacular in being really cheap to make, but I just don't know if it is possible. Williams went to 48V to get the extra kick for the flippers, bumpers and kickers. Things are a lot more efficient now, but you still run into the fact that you need a lot of turns and current to get a good pull on a solenoid, and the best way to increase current is to toss voltage at it. Using FETs instead of Darlingtons gives you back some of the power, but not a ton.

    I'll be interested in how it all works out.