(Topic ID: 118127)

What happens if you solder a coil backwards?


By mot

4 years ago



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  • 65 posts
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  • Latest reply 8 days ago by Walamab
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    #1 4 years ago

    I've got what feels like a very stupid question. I'm talking about solid states games, coils with a diode on the board (not on the coil). Particularly White Water. Particularly slingshots and bumpers. Not flippers.

    What happens if you solder a coil backwards? By that, I mean soldering the wires to the wrong lugs.

    My first thought was that the plunger would be pulled in the opposite direction, it'd clearly be wrong, and I'd need to reverse it back to how it was supposed to be. But now, I'm questioning if that's true.

    I guess I'm wondering how coils work... I had been assuming that a force was applied in one direction through the coil. My thought experiment was putting a bare pop bumper plunger in a coil, and firing the coil. I hypothesized that the plunger would fire out of the coil like a little rail gun in one particular direction. Then I started wondering how AC coils work and figured my hypothesis must be wrong. My new hypothesis, I suppose, is that the plunger would be pulled to the center of the coil, so depending on where it was before firing, it could be pulled in either direction. Is that right?

    Edit:
    Answer to my question: All coils pull the plunger to the center of the coil. They only pull and cannot push. If the coil does not have a diode on the coil (i.e. the diode is on the board), it does not matter which way it's wired. Thanks everyone!

    Post edited by mot: Answer to my questions

    #2 4 years ago

    I had this same question this week - don't think it's a dumb question at all. Probably pretty basic one for many people on here, but not all of us. [awaits wisdom]

    22
    #3 4 years ago

    No diode on the coil - doesn't matter.

    Diode on the coil - you blow crap up.

    LTG : )™

    #4 4 years ago

    On whitewater, i don't think anything will happen. I don't think there is a backwards. They'll do what they should do.

    #5 4 years ago

    There will be no difference to the coil.
    If a diode is on the coil, then the diode could be damaged if connected backwards, then the drive transistor.

    But I don't think that's what you are asking.
    Running electricity through a winding of wire creates a magnetic field. That field will draw the ferrite coil plunger toward it, always. There is no way to "push" with an electro-magnet. They only pull, like all magnets. The only exception is lining up to ferrite magnets, with like poles near each other.
    --
    Chris Hibler - CARGPB #31
    http://www.Team-EM.com
    http://webpages.charter.net/chibler/Pinball/index.htm
    http://www.PinWiki.com - The new place for pinball repair info

    #6 4 years ago

    I did this on my SW. Coil locked on and blew a bunch of stuff on the board. It's not a fun day when you see smoke coming out of your pin.

    -1
    #7 4 years ago

    There is def. a difference to the coil, I don't think the above is correct at all. The winding isn't an "electro-magnet -- it acts more like an inductor. Magnetic fields have direction, and because the coil is taking DC voltage, the current most certainly has a direction of flow from positive to ground. Using the right hand rule, point your thumb in the direction of the current and curl your fingers to find the direction of the magnetic field. The winding is all in one direction so you should be able to push or pull by switching the polarity of the lugs. For example, outlane kickbacks aren't pulling the plunger, they are pushing it away.

    The problem is that if you connect the wires backwards, you've probably just connected a positive 28 or 50 Vdc (depending on how old your pin is) to directly to ground since ground is common and often tied together for similar parts (high voltage and low voltage (IC's) would be isolated). If you shorted the path then the coil won't fire the other way, something will probably blow up first.. hopefully just a fuse.

    The diodes allow a path for the built up magnetic field to quickly dissipate. I believe without them you also risk high reverse voltages.. when you suddenly switch off current the magnetic field tries to support itself from collapse, which causes high reverse voltage spikes and has potential to damage things.

    #8 4 years ago
    Quoted from Mbecker:

    For example, outlane kickbacks aren't pulling the plunger, they are pushing it away.

    No, this is not correct. The kickbacks are VERY much being pulled into the coil. Every coil used operates by pulling in a metal plunger, and rely on a spring to push (or pull) the plunger to the start position once the electricity to the coil has been cut.

    #9 4 years ago
    Quoted from mot:

    I've got what feels like a very stupid question. I'm talking about solid states games, coils with a diode on the board (not on the coil). Particularly White Water. Particularly slingshots and bumpers. Not flippers.
    What happens if you solder a coil backwards? By that, I mean soldering the wires to the wrong lugs.
    My first thought was that the plunger would be pulled in the opposite direction, it'd clearly be wrong, and I'd need to reverse it back to how it was supposed to be. But now, I'm questioning if that's true.
    I guess I'm wondering how coils work... I had been assuming that a force was applied in one direction through the coil. My thought experiment was putting a bare pop bumper plunger in a coil, and firing the coil. I hypothesized that the plunger would fire out of the coil like a little rail gun in one particular direction. Then I started wondering how AC coils work and figured my hypothesis must be wrong. My new hypothesis, I suppose, is that the plunger would be pulled to the center of the coil, so depending on where it was before firing, it could be pulled in either direction. Is that right?

    Its obviously a great question judging by all the different responses.

    My theory.....give it a go and see what happens.....

    #10 4 years ago

    I've seen photos of exactly the same games with the coils wired different ways.

    On my AFM, for example, a couple of the pops are wired differently to a friends - at least that's what the photos show. Maybe one of our games isn't right - but both seem to work.

    #11 4 years ago

    My theory.....give it a go and see what happens.....

    No don't do it you'll have a popbumper cap hole in the ceiling.

    #12 4 years ago
    Quoted from mot:

    Particularly White Water. Particularly slingshots and bumpers

    I was going to say that J130 (J131+J132) and J127 (J128+J129) were always used for 50Volt solenoids (!) and (therefore) the diodes are on-board, so it doesn't matter how to connect the wires on the coil.
    (And yes, since the plungers are not magnets, the metal core is always pulled into the coil.)

    But then noticed a quite rare situation that 4 drivers in sol.#1-16 are used for flashers in this section and give a situation with mixed voltages next to each other on the headers and tabs.

    note: not power supply but voltage through coil and flash during rest.
    vio = 50 Vdc Solenoid
    red = 20 Vdc Flash
    blu = GND

    Not that it does give any problems, but good to know that taking measurements on a powered WhiteWater will give other readings than maybe expected
    J127-130.jpg

    25
    #13 4 years ago

    of course you can learn from this guy..................

    #14 4 years ago

    Did this to my Monopoly during a play field swap. Damaged 2 transistors on my board. Aggravating, but was a cheap fix that took me about 20 minutes. In the future I will take a better photo and double check before putting it back together.

    #15 4 years ago
    Quoted from dendoc:

    of course you can learn from this guy..................
    » YouTube video

    Wow some instruction video!!

    #16 4 years ago

    main thing is diode polarity being correct so things dont blow out. with DC electron flow (- to +) you might get a very slight difference in the electromagnetic coil's strength one way vs the other? I'd doubt it'd really be noticeable if there is an actual difference for that, it all being "light speed".

    #17 4 years ago

    Diodes across coils are positioned in a reverse direction of the current flow, and this is why you need to follow the + and - polarity when soldering the wires. Otherwise, there is no preferred polarity on a coil; when energized, it consumes current, converts it to magnetic pull and draws the armature in. Reverse its polarity it still consumes the same amount of current and same magnetic pull. As long as the armature doesn't retain any magnetic polarity (it is special material that doesn't) it will perform the same motion regardless of DC or AC polarity.

    The diode is in place to absorb a spike that occurs when a magnetic field collapses. Energy is stored in a copper winding when energized, and has to go somewhere when it is de-energized. The coil becomes a source of high voltage when the armature returns back to its parked position, and if you don't take it down with the diode, the voltage travels thru the circuit and potentially destroys the first piece of silicon it finds. That means a transistor or possibly several transistors can be affected. The spike generally exceeds the "breakdown voltage" spec of the transistor so it can kill a device in microseconds. And even though most diodes used on pins are rated at 400 volts, the spike can actually exceed that voltage and destroy that diode.

    Most driver transistor circuits include a diode on the PC board which further protects the driver from transient spikes, but not always. The larger the coil, the more severe the spike becomes.

    Solid state components have finite life when operated at or near their maximum rating. Heat vs. time is the factor that limits the life of that component.

    #18 4 years ago
    Quoted from Mbecker:

    The winding is all in one direction so you should be able to push or pull by switching the polarity of the lugs. For example, outlane kickbacks aren't pulling the plunger, they are pushing it away.

    Dude...I'd ask you to rethink this.
    http://en.wikipedia.org/wiki/Solenoid

    If you can design a coil that will PUSH a piece of ferrous metal away from it, your next job will be to develop cold nuclear fusion, and then to turn lead into gold.

    --
    Chris Hibler - CARGPB #31
    http://www.Team-EM.com
    http://webpages.charter.net/chibler/Pinball/index.htm
    http://www.PinWiki.com - The Place to go for Pinball Repair Info

    #19 4 years ago
    Quoted from ramegoom:

    Energy is stored in a copper winding when energized, and has to go somewhere when it is de-energized.

    and...think about the way that an alternator or generator works. They work because a magnetic field is placed near a coil. A pinball coil's magnetic field collapsing because the path to ground has been switched off is the same thing.
    --
    Chris Hibler - CARGPB #31
    http://www.Team-EM.com
    http://webpages.charter.net/chibler/Pinball/index.htm
    http://www.PinWiki.com - The Place to go for Pinball Repair Info

    #20 4 years ago

    great explanation ramegoom. some of that spike may also come from the solenoid return spring shoving the steel back out of the coil same moment power to the coil is cut? I've been tinkering with PMA wind power lately, coils and magnets basically making AC spikes.

    #21 4 years ago

    Now, if you were to pass a magnet thru the center of the flipper coil, you would then produce electric current. That would then be polarity-conscious. Your current would be DC in nature, and produce positive on one terminal of the coil. If you were to reverse the polarity of the magnet, you would then produce positive current on the other end of the coil. But we're not dealing with magnets, we're dealing with ferrous armatures that don't retain magnetism.

    Spikes can be a bitch...

    #22 4 years ago

    Chris -- hang on, I need to go edit that wiki article

    #23 4 years ago

    Dang, the rest of my post disappeared. I was incorrectly thinking of the armature as polarized in which case I think you could push or pull it since the direction of the induced field would reverse if you switch the wiring. But I do conceded Chris you were correct

    #24 4 years ago

    We need some more tutorials from mr unibrow. That was funny!
    He can work with Hank.

    #25 4 years ago

    This thread is pretty funny. A coil is simply a wire, wound from one lug to the other. The piece of wire couldn't care less which way it's connected. IT DOESN'T MATTER WHICH WAY YOU CONNECT THE WIRES TO A COIL *WITHOUT* A DIODE.

    Add a diode to the coil lugs, and it absolutely matters which way it's wired.

    --
    Rob Anthony
    Pinball Classics
    http://LockWhenLit.com
    Quality Board Work - In Home Service
    borygard at gmail dot com

    #26 4 years ago
    Quoted from Borygard:

    This thread is pretty funny. A coil is simply a wire, wound from one lug to the other. The piece of wire couldn't care less which way it's connected. IT DOESN'T MATTER WHICH WAY YOU CONNECT THE WIRES TO A COIL *WITHOUT* A DIODE.

    I admitted that I thought it was a stupid question, but I do appreciate your answer. You're one of the people I know I can trust!

    I hope you can understand how this image from Wikipedia confused me. I kept thinking about the right-hand rule, too!

    solenoid.png

    #27 4 years ago

    Nothing at all stupid about the question mot, or any question for that matter as far as I'm concerned. Some of the answers were what struck me as funny.

    --
    Rob Anthony
    Pinball Classics
    http://LockWhenLit.com
    Quality Board Work - In Home Service
    borygard at gmail dot com

    #28 4 years ago

    I still can't entirely make sense of this! Why doesn't the direction of the magnetic field matter?

    #29 4 years ago
    Quoted from mot:

    Why doesn't the direction of the magnetic field matter?

    The same reason why we don't fall off the Earth when we stand upside down. Most humans don't have polarity and are always attracted to the Earth. Even at the other side of the globe.

    #30 4 years ago
    Quoted from mot:

    I still can't entirely make sense of this! Why doesn't the direction of the magnetic field matter?

    Because the ferrous core (plunger link, etc.) doesn't have a magnetic polarity, it is attracted to either polarity the coil presents.

    #31 4 years ago
    Quoted from zaza:

    The same reason why we don't fall off the Earth when we stand upside down. Most humans don't have polarity and are always attracted to the Earth. Even at the other side of the globe.

    that would be gravity... polarity doesn't exist in that world... only mass matters...

    the reason we don't fall "through the earth" (at least to the center of mass of the system) is because of electricity... even the most solid looking of things is essentially empty space, and what makes them appear to be solid is good old electricity (all those electrons mutually repelling)....

    #32 4 years ago
    Quoted from bobukcat:

    Because the ferrous core (plunger link, etc.) doesn't have a magnetic polarity, it is attracted to either polarity the coil presents.

    technically speaking, a magnetic polarity is induced in the plunger by the magnetic field... if it had "no polarity" (e.g. electrons still scattered with random polarization, no alignment), it wouldn't work at all... the "attraction" would be offset by the "repelling"... for example, you couldn't use a plastic plunger... the magnetic field can't induce a polarity alignment in plastic, and the orientation remains random, thus the plunger goes nowhere...

    see this link:

    http://www.solenoid-valve-info.com/solenoid-valve-coil-polarity.html

    and read the last 2 paragraphs... they not only explain this, but explain why direction of current doesn't matter...

    #33 4 years ago

    There's exactly what I was looking for! Thank you!

    "If the current in the solenoid is now reversed, the magnetic field of the solenoid will reverse but, since the induced polarity of the plungers will also reverse, the direction of the pull on the plungers will be unchanged."

    #34 4 years ago

    A pinball coil is just a "coated" or "painted" piece of wire. The type of wire is commonly referred to as "magnet wire" outside of the pinball world. This is the type of wire used for 99% of all coils in everything in our world.

    As many others have suggested, the pinball coil (made of a coated piece of wire) does not care how the electricity flows. Only the implementation of a diode into the circuit matters. This is one major reason why some manufacturers removed the diodes from the playfield/coils, and moved them to the head, or on an additional daughter board with plugs.

    This way, it does not matter which wire is connected to which side of the coil, since when using that type of design, all the coils would be without a diode.

    THIS IS ALSO WHY THERE IS ALWAYS VOLTAGE ON ALL LUGS OF A COIL. The most common fallacy pinball people don't realize is that when a game is in play mode, all lugs of all coils ALWAYS have voltage. The GROUNDING of a coil is what determines a coil's actuation. Furthermore, the diode is what blocks that grounding action from affecting other components in that same circuit.

    Now, most flipper coils have two unique coil windings with two diodes, bot those coils use all these same principals to work.

    If all pinball owners trying to fix a coil problem knew these two simple facts and how to use a voltmeter, they would be able to fix a large majority of coil related pinball problems.

    Now, more modern pinball designers like 90's B/W, Stern and JerJack all use slightly modified designs to "cycle" how long coils ground for... This happens in hundredths or thousands of a second and is controlled by the MPU in a game... Think of that as more of an electric determination for the time that a coil is ON, rather than a physical. It is VERY similar to the difference between an analog power supply and a switching power supply.

    #35 4 years ago
    Quoted from snyper2099:

    Furthermore, the diode is what blocks that grounding from affecting other coils in that same circuit.

    The purpose of the diode is to prevent voltage spikes, which occur when ground is removed from the coil, from damaging the driver circuitry.

    #36 4 years ago
    Quoted from terryb:

    The purpose of the diode is to prevent voltage spikes, which occur when ground is removed from the coil, from damaging the driver circuitry.

    I don't follow. If you remove all the diodes from all the coils, voltage spikes are not the only consequence.

    Oh, I think I understand what you're saying now, I fixed it. Meant to type components, not "coils".

    #37 4 years ago
    Quoted from snyper2099:

    I don't follow. If you remove all the diodes from all the coils, voltage spikes are not the only consequence.

    Coils can share a single power wire, but they all have separate grounding transistors. They are not "in the same circuit".

    #38 4 years ago

    I was using a coilgun (Gauss rifle) as part of my thought experiment, but I had misconceptions about how they worked. I incorrectly assumed that the magnetic field pushed in one direction. In reality, the projectile can only be pulled by the magnets, and precise timing is needed to pull the projectile to accelerate it, and shut off before it will cause it to decelerate.

    Now that I've thought about this a bunch, I've got a better idea how the accelerator on No Fear and The Getaway work, too!

    Gauss Rifle

    #39 4 years ago

    question has been well answered already.

    just wanted to tell dendoc thanks for sharing

    video is hilarious

    #40 4 years ago
    Quoted from mot:

    I incorrectly assumed that the magnetic field pushed in one direction. In reality, the projectile can only be pulled by the magnets

    Correct. Always pulling. In your picture, if any of those coils were flipped around so the blue end was in the back and red in the front, it wouldn't matter.

    Coils.jpg

    #41 4 years ago

    Now let's build a super fast train =)

    #42 4 years ago
    Quoted from mot:

    I was using a coilgun (Gauss rifle) as part of my thought experiment, but I had misconceptions about how they worked. I incorrectly assumed that the magnetic field pushed in one direction. In reality, the projectile can only be pulled by the magnets, and precise timing is needed to pull the projectile to accelerate it, and shut off before it will cause it to decelerate.
    Now that I've thought about this a bunch, I've got a better idea how the accelerator looks on No Fear and The Getaway work, too!

    Exactly. That is exactly how the "Getaway: High Speed 2" supercharger and the No Fear Jump ramps work...three coils timed perfectly.
    --
    Chris Hibler - CARGPB #31
    http://www.Team-EM.com
    http://webpages.chartet.net/chibler/Pinball/index.htm
    http://www.PinWiki.com - The Place to go for Pinball Repair Info

    #43 4 years ago
    Quoted from ccotenj:

    technically speaking, a magnetic polarity is induced in the plunger by the magnetic field... if it had "no polarity" (e.g. electrons still scattered with random polarization, no alignment), it wouldn't work at all... the "attraction" would be offset by the "repelling"... for example, you couldn't use a plastic plunger... the magnetic field can't induce a polarity alignment in plastic, and the orientation remains random, thus the plunger goes nowhere...
    see this link:
    http://www.solenoid-valve-info.com/solenoid-valve-coil-polarity.html
    and read the last 2 paragraphs... they not only explain this, but explain why direction of current doesn't matter...

    Of course it wouldn't work with a plunger that is not attracted to a magnetic field, but if that plunger DOES have a significant magnetic polarization to begin with, i.e. it IS a magnet, then the polarization of the current through the coil would matter as it would either attract or repel said magnet based on polarization of the field generated when energized, agreed?

    #44 4 years ago

    So how does the diode absorb the spike?
    Does it turn most of the spike to heat?

    #45 4 years ago
    Quoted from fnosm:

    So how does the diode absorb the spike?

    It lets it go one way but not the other. The not the other way is what saves the transistor.

    LTG : )™

    #46 4 years ago

    Like crossing the streams, it would be bad… Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.

    #47 4 years ago
    Quoted from LTG:

    It lets it go one way but not the other.

    Yeah but it lets it go right back to the power side. I know what actually makes it through the diode is a lot less than what hits the diode. I am curious to know where that difference goes? Heat?

    #48 4 years ago
    Quoted from bobukcat:

    Of course it wouldn't work with a plunger that is not attracted to a magnetic field, but if that plunger DOES have a significant magnetic polarization to begin with, i.e. it IS a magnet, then the polarization of the current through the coil would matter as it would either attract or repel said magnet based on polarization of the field generated when energized, agreed?

    sure... at least until you pump enough energy into the generated magnetic field...

    but plungers aren't permanent magnets... their magnetic domains are random, until acted upon by an external force... when exposed to an external force (a magnetic field) their magnetic domains line up, creating a temporary polarization of the material... since the energy contained in the magnetic field is small, when the external magnetic field collapses, the period of hysteresis for the plunger is VERY short, and it essentially returns to a random magnetic domain state instantly...

    his question was: why doesn't it matter what direction the current goes for a plunger? it is because a plunger isn't a permanent magnet, but it is made of materials that allow it to become temporarily magnetized... and because the "direction" of the magnetic domain alignment is entirely dependent upon the external force, the induced alignment will ALWAYS force the plunger to "pull in"...

    #49 4 years ago
    Quoted from fnosm:

    So how does the diode absorb the spike?

    The diode doesn't absorb the spike per se. It causes the current to loop through the diode and coil over and over and over until the voltage is dissipated by the (small) resistance in the coil.

    Here's a pretty good article about how this is used in other applications to protect the driving circuit.

    http://en.wikipedia.org/wiki/Flyback_diode

    Post edited by txx3ddq442: forgot the link

    #50 4 years ago
    Quoted from txx3ddq442:

    The diode doesn't absorb the spike per se. It causes the current to loop through the diode and coil over and over and over until the voltage is dissipated by the (small) resistance in the coil.

    Thanks txx.

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