Hot glue on the motherboard coils

[AmberClad]

I wish I had a camera to take a picture of what I'm referring to. It basically looks like they coated the coil with hot glue, then stuck a rubber or plastic square around the coil.

If it's intended to be short circuit protection, then it's not a very effective way to achieve it, since the top of the coil is still completely exposed. The coils themselves are a little non-standard too. They're shaped like a compressed spring, instead of being wrapped around a plastic "donut" like you'd normally see.

 

[SerpentRoyal]

Noise...coils will oscillate under use.

 

[Viper GTS]

Originally posted by: SerpentRoyal
Noise...coils will oscillate under use.

Yup. Ever heard a whining motherboard? It's seriously obnoxious.

Viper GTS

 

[AmberClad]

Wouldn't wrapping the coils around a rubber donut achieve the same purpose? Submerging nearly the whole choke coil in glue doesn't seem like it would be the best idea, as far as heat dissipation is concerned.

 

[Aluvus]

Originally posted by: AmberClad
Wouldn't wrapping the coils around a rubber donut achieve the same purpose? Submerging nearly the whole choke coil in glue doesn't seem like it would be the best idea, as far as heat dissipation is concerned.

Unless something is very wrong, an inductor should have very little resistance, and consequently should consume relatively little real power. Which means not much heat to deal with.

Some inductors are wound around, say, a ferrous "donut" because this produces a higher inductance (all things being equal) than an "air core". However, in such a configuration it's just as possible for the wire to vibrate against the ferrite core and make noise. The hot glue (which is sometimes seen on "donut" inductors as well) provides damping. Since the vibration that creates "coil whine" is high frequency, that damping is a pretty effective way to deal with it.

The relevant Wikipedia article has some pictures of different inductor types, and a reasonably useful description.

 

[AmberClad]

I knew I should have paid closer attention during those physics courses . So it sounds like it's essentially a tradeoff between better inductance vs eliminating coil noise.

 

[bruceb]

Glue or wax on coils has been common practice especially in radio circuits.
In radios, quite often, you fine tune the reasonance frequency by changing the
spacing of the coil windings. Once you set it the way it needs to be, a dab of
wax or glue, holds it in place so it can't change. And you have nothing to worry
about as far as heat is concerned.

 

[AmberClad]

Come to think of it, I've seen heatshrink tubing used on coils too (the donut variety), but only in PSUs (presumably for the same reasons?). I personally haven't see it used on motherboards though, for whatever reason.

And I did finally find a pic of what I'm referring. It's not the same board, but it is the same type of hot-glued coils.

 

[jonmcc33]

Amber, why don't you leave the motherboard manufacturing to the motherboard manufacturers? I'm pretty sure that they have some sort of clue about what they are doing.

 

[AmberClad]

Oh come on, it's not like I was asking how to melt off the glue and pry off that plastic cube . Just curious, is all.

I do admit that there is no coil whine, and that it could theoretically be due to the hot-glue coils, and that therefore the motherboard manufacturer might possibly know what they're doing. There, ya happy ?

 

[wwswimming]

Originally posted by: AmberClad
So it sounds like it's essentially a tradeoff between better inductance vs eliminating coil noise.

and cost. the toroidal shaped inductors are usually
more labor intensive to make.

once i was sitting in a cafe in Berkeley - winding
inductors or transformers. i had just taken a second
class in electromagnetics and was crazed with div,
curl, and vector calculus.

a woman with long blonde hair looked over and asked
me what i was doing. ignorring the guy she was with,
i told her i was winding transformers. she said it looked
like macrame.

then they came over to my table. when the guy stood
up, i realized - it was Steve Jobs. it was his fiancee i
was checking out.

oh, and also, in a critical situation, like an airborne
high voltage power supply, the inductor and transformer
cores have a tendency to crack; the material is weak in
tension. it's a lot easier to keep a toroid shaped inductor
core in a state of compression (where it is happiest).

which has very little application to desktop computer
motherboards.

 

[AmberClad]

Originally posted by: wwswimming
The toroidal shaped inductors are usually
more labor intensive to make.

Which type of inductor is a "toroidal" shaped one you're referring to? The one that are wound around a torus, or the type that are coiled into a torus?

Originally posted by: wwswimming
a woman with long blonde hair looked over and asked
me what i was doing. ignorring the guy she was with,
i told her i was winding transformers. she said it looked
like macrame.

then they came over to my table. when the guy stood
up, i realized - it was Steve Jobs. it was his fiancee i
was checking out.

They were probably hoping that you were making one of these ...

 

[wwswimming]

Which type of inductor is a "toroidal" shaped one you're referring to? The one that are wound around a torus, or the type that are coiled into a torus?

They were probably hoping that you were making one of these ...

^ macrame ipod holder, if anyone is interested.

- - -

the ones that are wound around a torus.

coiled into a torus ? having a little trouble visualizing that.

pictures of ones i made -

http://www.geocities.com/wwswimming/toroid3.JPG

the toroid with orange and blue wire (intel colors take that
AMD fanboys, don't worry i have some green wire somewhere)
is designed for 60 Hz. (steel core)

the small one is designed for a switching frequency
of about 100 kHz. (ferrite core)

the Borg cube looking transformer core, the thing
on the far right (not a toroid) ... the guys i worked
with called them "pot cores". the aluminum thing is
a heat sink, part of it to cool the core, part of it to
cool the copper.

actually, that cafe meeting was about 20 years ago.
way pre-ipod, post Mac introduction. is there a Mac
macrame ? there has to be.

http://images.google.com/image...mputer+macrame&ndsp=20

... but i didn't find one.

then a few years later Herb Caen announced in the San
Francisco Chronicle that Mr. Jobs had been in to Gump's
in SF and spent $250K on an engagement ring.

obviously not following the 2 month salary guideline !

 

[jonmcc33]

Originally posted by: AmberClad
Oh come on, it's not like I was asking how to melt off the glue and pry off that plastic cube . Just curious, is all.

I do admit that there is no coil whine, and that it could theoretically be due to the hot-glue coils, and that therefore the motherboard manufacturer might possibly know what they're doing. There, ya happy ?

Sounds to me like you were trying to reinvent the wheel.