(Topic ID: 279915)

Removing windings from EM solenoids

By MarkG

3 years ago


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  • 18 posts
  • 11 Pinsiders participating
  • Latest reply 3 years ago by astyy
  • Topic is favorited by 7 Pinsiders

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    #1 3 years ago

    I've often heard of folks removing windings or wire loops from solenoids in their EM games to get a little more oomph and wondered how that works. I don't disagree that it does work but I wanted to understand it better than I did. I haven't read an explanation that really convinced me. I had my own theories but they involved a lot of hand waving and assumptions.

    After taking a few runs at looking for an answer I finally took a stab at doing an experiment and studying the results myself. Here's the jig I put together for the experiment:
    CoilStrengthJig (resized).jpgCoilStrengthJig (resized).jpg
    It turns out that there's a lot going on and it can turn into a real rabbit hole. That may explain why I couldn't find a simple satisfying answer.

    I also learned a few unexpected things along the way. Ever wonder why a flip seems stronger or weaker every now and then? I gathered up the highlights and tried explain the important bits in an intuitive way without getting bogged down in the math. It's probably still way more than most want to know.

    But if you're still curious the whole saga is at:
    https://www.funwithpinball.com/learn/solenoid-strength-test

    /Mark

    #2 3 years ago

    Hey Mark,

    Thanks for the great writeup. I never realized that solenoid strength varied so much. Your explanation about timing relative to the 60 cycle makes perfect sense though. That factor could be overcome in your setup in at least a couple ways I can think of, but with your EE background you probably already thought of them.

    H.

    #3 3 years ago

    That was fascinating reading, Mark - thanks so much for doing all the work! You have a gift for explaining technical issues - your explanations of schematic circuits in the pinball machines you help people troubleshoot on this site are always clear and concise. I'm glad you're out there helping to demystify these machines for those of us that want to repair them and keep them working.

    I've removed layers of wire successfully on a "Slick Chick". The change wasn't too dramatic, but it was enough that the ball could get back up to the top of the playfield through pop bumper action, which made a huge difference in the way the game played. Luckily, each of the pops on that game are activated individually, so I didn't have to worry too much about excess current that you mentioned could be possible if multiple pops are activated together. I just removed half a layer at a time until I got the action that I wanted...just experimentally decided how much to remove.

    It's great to read about what's going on done in a more controlled scientific manner. Thanks for doing that so well!

    #4 3 years ago

    Veddy interesting!!

    That said ... I didn't notice any difference the time I did it on one pop (Williams Klondike) and on top of that it was an ultra-PITA.

    #5 3 years ago

    Wow, well done.
    Thanks for sharing.

    #6 3 years ago

    Very cool research, thanks! Another real-world physics aspect that a virtual experience will not emulate (until they incorporate a 60Hz clock and futz the solenoid power against it!)

    #7 3 years ago

    So Mark - since the flippers are also AC, that same inconsistency of power must happen with them as well? There are so many variables changing each time the ball is on a flipper that it would be hard to tell in the real world, but they must also be subject to that same difference in where the AC wave is when the pull begins, right?

    And as you remove windings and lower the inductive reactance, allowing the current to change direction more quickly, would the coil fire just a little bit faster as well as more powerfully, as you go down that path - even if just a miniscule amount?

    #8 3 years ago

    Thanks for the kind words everyone.

    Quoted from HowardR:

    That factor could be overcome in your setup in at least a couple ways I can think of,

    There certainly are ways to chase out the voltage variability but they wouldn't accurately represent what's going on in AC solenoids. DC solenoids are probably more consistent. I may look into that some but like I mentioned earlier,... rabbit hole.

    Quoted from currieddog:

    and on top of that it was an ultra-PITA.

    Roger that. I didn't want to alter the test jig so I removed and reinstalled the solenoid in its bracket without moving anything else. A few choice words may have been used.

    Quoted from paulace:

    since the flippers are also AC, that same inconsistency of power must happen with them as well? There are so many variables changing each time the ball is on a flipper that it would be hard to tell in the real world, but they must also be subject to that same difference in where the AC wave is when the pull begins, right?

    I'm pretty sure that all AC solenoids and coils are subject to the same inconsistency. The engineering challenge is to design the system to accommodate the variability. On a relay coil you'd need to be sure that even the worst case delay could be tolerated before the relay switches needed to be activated. On playfield solenoids they'd need to be strong enough to get the ball to its next bounce fast enough that the player wouldn't notice the variability most of the time.

    Quoted from paulace:

    And as you remove windings and lower the inductive reactance, allowing the current to change direction more quickly, would the coil fire just a little bit faster as well as more powerfully, as you go down that path - even if just a miniscule amount?

    I think with fewer windings you get more current and therefore more power but the current doesn't really change any sooner. In an inductor (or solenoid) the change in current always trails the change in voltage (by 90 degrees, but only for an ideal inductor) because the current has the extra work of having to build or tear down the magnetic field.

    #9 3 years ago

    The question of how AC and DC results might differ was nagging at me so I tried an abbreviated experiment with a DC supply. The short answer is that a DC supply gives a more consistent kick than an AC supply as you might expect. More details in the write up.

    #10 3 years ago
    Quoted from currieddog:

    Veddy interesting!!
    That said ... I didn't notice any difference the time I did it on one pop (Williams Klondike) and on top of that it was an ultra-PITA.

    If you didn't notice any difference you didn't take off enough turns.

    It's not a difficult thing to do. Cut the wrapper and cut the outside wire and start unwinding. Just check once in awhile to make sure you aren't taking too much off and end up with a dead short. Use a multimeter to check your starting and ending resistance. All there is to it.

    Removing turns of wires lowers the resistance and under Ohm's law lowering resistance with voltage staying constant increases current and thus power.

    #11 3 years ago
    Quoted from EMsInKC:

    If you didn't notice any difference you didn't take off enough turns.

    I, and a good number of other Pinsiders, don't really care what you think.

    #12 3 years ago
    Quoted from currieddog:

    I, and a good number of other Pinsiders, don't really care what you think.

    No problem. A number of other people here would tell you if you did it and didn't notice a difference you didn't do it right but it certainly wouldn't be the first time.

    #13 3 years ago

    I'd explain, but you have no tact or class and it would be a waste. We'd all be glad if you found another pursuit, such as scrapbooking.

    #14 3 years ago
    Quoted from currieddog:

    I'd explain, but you have no tact or class and it would be a waste. We'd all be glad if you found another pursuit.

    No class. Wow. Pull out the big guns next time.

    #15 3 years ago

    Hi pinsiders
    I do not like to downvote - so I upvoted a post.
    About unwinding one or two layers off a coil --- I read about, didn't believe - worked me out the solution "each bumper-coil gets its own rectifier" - with an minimum of altering wiring in the pin: The bumpers in my Shangri La changed from sluggish to lively. Greetings Rolf

    0Shangri-La-Bumper-ori-01 (resized).JPG0Shangri-La-Bumper-ori-01 (resized).JPG0Shangri-La-Bumper-DC-Work-EN (resized).jpg0Shangri-La-Bumper-DC-Work-EN (resized).jpg
    #16 3 years ago

    After reading about this on Pinrepair, I tried it, though only taking 2 turns of wire off, and it made a worthwhile improvement on a GTB Central Park. As has been said measure the coils before you begin so you know they all sound.

    #17 3 years ago

    On GTB pops and slings I have removed 3 winding layers with great results. Removing more than 3 layers might decrease the coil resistance too far for it to work.

    #18 3 years ago

    Great article and experiment, reminded me of this earlier thread with good discussion and a formula for this;
    https://pinside.com/pinball/forum/topic/increasing-the-power-to-a-coil-remove-more-windings

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