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(Topic ID: 218501)

Cooling off flippers with a fan?


By KurtWehrli

2 years ago



Topic Stats

  • 71 posts
  • 32 Pinsiders participating
  • Latest reply 2 years ago by MrBally
  • Topic is favorited by 3 Pinsiders

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    #51 2 years ago
    Quoted from barakandl:

    Seems like games with this setup are the only one I have seen coils heat up to the point is causes a flipper strength problem.
    My baywatch had an issue with coils heating up and causing them lose power. I put a couple of 12v fans taken from old computer boxes and have them blowing on the flipper coils. It really does help with the flipper power giving out after many games in a row.
    I found a cable with 120v on it in the cabinet. I think it was for a bill acceptor or whatever. I used that to connect to a 12v wall wart to power the fans only when the game is on.

    If you get a chance I’d love to see a picture of your cooling setup on Baywatch. My flipper strength diminishes too after awhile of playing and this may be just what I’m looking for.

    -1
    #52 2 years ago
    Quoted from mbwalker:

    Hi Guys,
    This topic really caught my attention because I deal with this daily and thought it was very interesting. Can it be true? Let's take a closer look. Apologies for a slightly long winded thread.
    First off: I'm not a thermal engineer, but rather a EE. But I design with it in mind. Thermal engineers don't tell me what to do, but rather did I do it right? I need to get the heat out of a part to the thermal guys so they can deal with it. No means an expert, far from it. But I design with an understanding of it and maybe I can clarify some of the comments here at the '70,000 ft level'. Not entirely from a flipper/solenoid standpoint, but a thermal issue in general - but it does apply to solenoids (and even transistors and heatsinks) so I will try to focus on solenoids and I hope you find it interesting. The 'things' I design can dissipate upwards of of ~700W in the space of a thumbnail. Ouch! Getting the heat out HAS to happen...no "if, and, or buts" about it or it's a 'bad design day' with big ramifications.
    So here it goes...
    1st important topic: Kurt and others mentioned thermal expansion, which is a real issue. But we will assume that is not an issue here (or could be easily determined) - but I surely won't discount his (and others) comment because it is valid concern, just maybe not here. Let's assume everything remains friction free.
    2nd important topic: Thermal resistance. This is a key aspect and directly relates to the coil temperature (but it gets more complicated in a bit!). This is measured (in my case) C/W (celsius/ per watt) into an ambient thermal sink. In other words, if the thermal resistance of a device (i.e a solenoid) is 10C/watt...for every watt dissipated in a device, the device temperature rises 10 deg celsius. NO clue what a coil dissipates, NOR the C/W, but C/W is the standard by what we go by. Let's say for argument's sake a coil really is 10C/W (into a heatsink). Also let's say it dissipates 5W, that would equate to a 50 C rise in coil temperature...but where does it go? Another heatsink (great)? Or just air (bad)? That is an important question. Everything has a thermal resistance. Let's say there was a heatsink to cool a flipper coil - that connection between the heatsink and flipper also has a C/W number assigned to it and it's not perfect - it can't dump all 100% of the heat. Of course, we all know there's no heatsink to the outside world in a flipper coil - it's all sort of stuck there all by itself w/heat going nowhere, which means the C/W is actually higher since most manufacturers quote C/W into a heatsink. At least the parts I deal with do, don't know about solenoids. Sure, there's metal around it with the brackets, plunger in the middle, etc...but no direct thermal path (i.e. low C/W path) between it and something else...so honestly - I'd write all that off as thermally not connected and it falls out of our of the equation entirely. So whatever the C/W is in air..that's what it is. A coil is a nice little heat source with no where to go, and therefore, it gets hot! Some manufactures only quote the C/W into an ideal (translate: doesn't exist) heatsink.
    3rd important topic: The C/W I mentioned above...guess what? It's not uniform. It varies in the depth of coil windings (yeah, now it is getting a little more complicated, but hold on it gets worse). At least the windings near the outside have air it can dissipate into. But air thermally sucks compared to metal, plus there's no air FLOW across. So almost nearly terrible as nothing, but at least there is stagnant air, for what it's barely worth (ugh!). What about the windings inside the coil? There is zero air movement there and basically zero thermal path. The insulation on the winding has a C/W that basically acts like thermal insulator. The nylon sleeve..great thermal insulator too. The plastic form? Forget it thermally - useless. The bottom line..it can get hot and the only way to tell what's going on in there is to insert a thermal probe in the coil itself and measure (which would make a great white paper). If people mention the outside of the coil is toasty, the inside will be REALLY toasty. Thermal resistance of the wire itself (i.e. heat in one end, heat out the other end) is so high it doesn't count unless maybe the wire is ~0.5 inch long - doesn't apply here. Bottom line- the coil is really sitting there all by itself thermally with no place for the heat to go. Wait...we're not done...it's get's slightly more complicated.
    4th important topic: So what about the wire? Nerd alert. Copper wire has a thermal coefficient of resistance of +0.00393 per C based on 25C (room temperature). Simply put, as the coil increases temperature (remember it can really heat up on the inside of the coil?), the resistance will increase, current therefore will decrease (more on that later). Spoiler alert: Generically speaking...YES, the coil will become less 'powerful' as it heats up since it is drawing less current. Therefore, it will actually will cool down slightly due to self-regulating w/respect to temperature, which means it will then get hot again since the resistance lowers, which means it will cool down again, which means... Wait, what did I just say? Now even I'm getting getting confused myself! OK, nitpicking there with minor details.
    5th important topic: "So my coil draws less current when hot and becomes wimpy, HA! I knew it!" Maybe...the other piece of the puzzle is what about the transistor or FET that drives the coil? It is essential acts as a very small resistor when on. When you draw less current, it drops less voltage and the coil gets a little more voltage which which inherently helps the coil gain just a bit back in current. Not much, but it does happen with a cheap transistor (that's why some transistors have a heatsink). But it can't be ignored. BTW, in this case, the 'on' resistance can be referred to as the 'source impedance'. The rail voltage also has a source impedance, but should be fairly low. There's also some thermal aspects of the driver transistor/FET which I won't cover which can impact the the 'on' resistance on the transistor.
    6th important topic: Let's not forget, exactly "How hot is the wire getting and how does it impact resistance?" 1%? 10%? 20%? Real temperatures are needed, not "it's hot" because it doesn't hold its weight (not picking on anyone ). But it is very important to this discussion.
    So let's wrap this up: Theoretically, YES a fan can help. The thermal resistance of everything in the coil/bracket/etc. still royally sucks - but on paper, a fan blowing air on the coil will make a difference, the solenoid will be cooler. I hear the grumbles already - "you're full of BS". I'd be the first one to say 'won't help much', but at the same time it DOES help. If it's enough, then 'good for you'. It sure doesn't make it worse. In this case, cooler is better. Pulsing coils and a low power switch mode on a coil can also help immensely. Again, I'm not going to cover it in depth.
    In closing, I've just barely scratched the surface. But perhaps I've shed a little light on what's going on. Please don't nitpick my comments - I get it, but I wanted to keep it at a simple level for everyone (and I'm very tired of typing and it's getting late) in at least a somewhat brief explanation (failed at that). This can easily turn into a Ph.D topic if warranted!
    There will be a test later!
    Regards,
    Mark

    According to others this thread was exclusively about single wound coils not the multiple sources of potential heat, their causes, or solutions although never mentioned by the OP.

    The rest is just "technical crap" so I guess it simply will remain a complete mystery to professional mechanical/manufacturing engineers, despite some working on direct applications for thermodynamic cooling along with fluid and mass transfer in heavy industry.

    PinSide does not promote forms of education, especially to those are blind to its actual value.

    #53 2 years ago
    Quoted from xTheBlackKnightx:

    If someone wants to make a new type of improved flipper assembly or even a better electrmagnetic coil (with baffling or fins), I welcome the innovation.

    I have a design that does away with the end stop, this allows the plunger to draw air through the coil cooling it.

    #54 2 years ago

    I'm going to back this down do a more basic level with some thoughts:

    I can play the shit out of my B/W games (dual coil designs) and the flipper coils never fade - they never even get warm.
    I can play the shit out of DE Maverick and the coils never fade (single coil design DE/Sega - high power coil drops to low voltage hold after non variable 40ms)

    LOTR is often mentioned as having flipper fade,
    - service bulletin points to a software upgrade
    - Pinballlifes special coil has solved flipper fade for many LOTR owners
    https://www.pinballlife.com/index.php?p=product&id=1112&parent=73

    A Pinside LOTR owners comment:
    Mine are stock and the strength is normal...
    No problems DTR past the 45 minute mark.
    Even with multiple players, it hasn't seemed to fade too much. Maybe I got a lucky one???

    Flipper fade is assumed to be caused by the coils inability to dissipate excess heat (proven because adding a fan relieves the symptoms)
    What then, is the root cause of the flipper coils in some game titles getting too hot but not others?...and why are there some owners of those titles not having the problem?

    #55 2 years ago

    Inconsistent reports are often due to a non-controlled study. As well, get two people into conversation and you eventually get three opinions.

    #56 2 years ago
    Quoted from xTheBlackKnightx:

    More
    According to others this thread was exclusively about single wound coils not the multiple sources of potential heat, their causes, or solutions although never mentioned by the OP.
    The rest is just "technical crap" so I guess it simply will remain a complete mystery to professional mechanical/manufacturing engineers, despite some working on direct applications for thermodynamic cooling along with fluid and mass transfer in heavy industry.
    PinSide does not promote forms of education, especially to those are blind to its actual value.

    Here we go...

    it’s a shame that the “average” collecting community (and general people that play pinball, including those that want to own it but not spend their time fixing it) are such a thorn in the side of “real collectors.”

    Just baffles the mind why someone would carry such a distaste for the entire buying community as a whole. Just be happy and respect folks for who they are. Geesh

    #57 2 years ago

    .

    12
    #58 2 years ago
    Quoted from xTheBlackKnightx:

    More
    According to others this thread was exclusively about single wound coils not the multiple sources of potential heat, their causes, or solutions although never mentioned by the OP.
    The rest is just "technical crap" so I guess it simply will remain a complete mystery to professional mechanical/manufacturing engineers, despite some working on direct applications for thermodynamic cooling along with fluid and mass transfer in heavy industry.
    PinSide does not promote forms of education, especially to those are blind to its actual value.

    My explanation was discussing single wound coils, and a single heat source.

    "Pinside does not promote forms of education." Thanks for letting me know that. Nor does it prohibit them. After all, this is the "Technical Forum", correct?

    I conveyed information that the OP might have thought was interesting. If not, no big deal. It was long, probably boring as all get out, and I surely don't mind if people don't read it.

    Technical crap? I'm going to quote 27dnast above.... "Geesh"

    Please accept my apologies for posting.

    #59 2 years ago
    Quoted from mbwalker:

    My explanation was discussing single wound coils, and a single heat source.
    "Pinside does not promote forms of education." Thanks for letting me know that. Nor does it prohibit them. After all, this is the "Technical Forum", correct?
    I conveyed information that the OP might have thought was interesting. If not, no big deal. It was long, probably boring as all get out, and I surely don't mind if people don't read it.
    Technical crap? I'm going to quote 27dnast above.... "Geesh"
    Please accept my apologies for posting.

    It was an interesting read, though a bit long. Don't stop posting as many others have because of the din.

    #60 2 years ago
    Quoted from mbwalker:

    More
    My explanation was discussing single wound coils, and a single heat source.
    "Pinside does not promote forms of education." Thanks for letting me know that. Nor does it prohibit them. After all, this is the "Technical Forum", correct?
    I conveyed information that the OP might have thought was interesting. If not, no big deal. It was long, probably boring as all get out, and I surely don't mind if people don't read it.
    Technical crap? I'm going to quote 27dnast above.... "Geesh"
    Please accept my apologies for posting.

    Keep it coming! Don't listening to the noise.

    It's so sad that someone has to be so negative on the vast majority of the collecting community. This archaic and detrimental viewpoint that pinball is really only appreciated or understood by a chosen few is a mound of BS. It's weak and unnecessary. Unfortunately, the Black Knight feels the need to delineate every chance he gets.

    Screen Shot 2018-06-07 at 1.29.59 PM (resized).png
    #61 2 years ago

    Single wound coil? In K2S0 voice," sounds like a bad idea to me"

    Is this a contributor to the loud annoying buzz sound? I have noticed on several twitch streams machines with the flipper on hold making a very loud buzz. Spiderman, GoT, TWD and at least a few others.

    It sounds horrible.

    #62 2 years ago
    Quoted from xTheBlackKnightx:

    It is estimated that a clean coil sleeve and polished plunger, and rebuilt parts can increase coil power by an average 25-40% dependent on manufacturer and era. Measured by a force gauge meter after restorations.

    So, where did you get this info?

    #63 2 years ago
    Quoted from mbwalker:

    More
    My explanation was discussing single wound coils, and a single heat source.
    "Pinside does not promote forms of education." Thanks for letting me know that. Nor does it prohibit them. After all, this is the "Technical Forum", correct?
    I conveyed information that the OP might have thought was interesting. If not, no big deal. It was long, probably boring as all get out, and I surely don't mind if people don't read it.
    Technical crap? I'm going to quote 27dnast above.... "Geesh"
    Please accept my apologies for posting.

    I enjoyed reading your post, don't stop!

    #64 2 years ago

    I like pie. With Ice cream.....

    #66 2 years ago

    I'm surprised that no one has put together a durable inexpensive mod to apply airflow over flipper coils.

    I'd buy it for my WOZ and Hobbit.
    I'm just too busy and too lazy to put something together right now.

    #67 2 years ago
    Quoted from pinballinreno:

    I'm surprised that no one has put together a durable inexpensive mod to apply airflow over flipper coils.
    I'd buy it for my WOZ and Hobbit.
    I'm just too busy and too lazy to put something together right now.

    Fans and other cooling methods may be options to address symptoms, that's ok for some but it doesn't sit right with me. I'd rather see solutions that address single wound coils getting hot in the first place.
    Is the only solution other than addressing the heat to revert to the stay-cool dual coil?...or can we modify the single wound designs to not get hot in the first place with changes to circuitry, software, or the coil itself?

    #68 2 years ago
    Quoted from wayout440:

    Fans and other cooling methods may be options to address symptoms, that's ok for some but it doesn't sit right with me. I'd rather see solutions that address single wound coils getting hot in the first place.
    Is the only solution other than addressing the heat to revert to the stay-cool dual coil?...or can we modify the single wound designs to not get hot in the first place with changes to circuitry, software, or the coil itself?

    Hi Wayout,

    Yes and no (and I promise not go all wordy and will refrain from using much technical crap). I would doubt if anyone would want to do it, it's not really a DIY fix. If a 'weak coil' is from the wire increasing resistance, then one fix would be to automatically increase the voltage going to the coil based on coil temperature. Several ways to accomplish this, but hardly a common sense approach for a hobbiest and I don't see this as an option unless someone wants to make an aftermarket mod. Plus the machine might not even support it.

    A heatsink with thermal grease (or a thermally conductive material) might also work, but really only if air was moving across it, plus space or other things in the way really limits a person's options. Even if you could buy one, it would be a WAG (wild ass guess) without at least doing some basic thermal analysis.

    If a fan doesn't cut it, them perhaps the dual coil approach is the most practical. I would think someone would have already made one of these for aftermarket installs.

    In the end, I assume some coils are more susceptible than others. I don't know if anyone has really looked extensively into coils vs. temperature, but likely not many in the hobby community.

    Heat in the coil is just a fact of life. Basic Ohm's Law. A coil takes a fair amount of current, and it has resistance, so heat is a natural byproduct. If the machine has software driving the coils, then maybe someone could mod the software to help limit the heat. Again, not a DIY. I'm probably leaving out some other options.

    I actually have a FLIR (an infrared camera for temperature measurement). If anyone is interested, I might snap some pictures of the solenoids at early game play and again after a good workout. Here's an example of my JD backbox

    Mark
    img_thermal_1528424915358 (resized).jpgjd_backbox (resized).jpg

    #69 2 years ago
    Quoted from KoolFingers:

    More
    It was an interesting read, though a bit long...

    As soon as I started typing I thought "Yeah, this is going to be a lot of typing and way too much info." I tried to make it simple and give easy to understand examples for those interested. Hard to do that in a few words, so I just trudged on thru it. Won't ever get that hour back, !

    #70 2 years ago
    Quoted from MrBally:

    I like pie. With Ice cream.....

    As in "A La Mode"?

    #71 2 years ago

    This is a pinball site.....

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