Basic DC Controllers

[Hobby]

Showing what a coreless motor looks like in the flesh, the one that causes so may issues for some controllers and which we've been discussing. I've never seen one "broken down" before so was quite interested. OK not completely OT but quite relevant?

[Stefan Krebs]

Gentlemen,

It's got EVERYTHING to do with the thread, you just need to look properly!  :laugh:

Don't you see the mass of the anchor, and its diameter? What inertia?
Don't you notice the poles and the brushes?

Compare these details with the traditional motor we all know! Is it realistic to expect a 'basic DC controller' to work well with both types of motors? Especially, as 'basic' implies that such controller is unlikely to deliver smooth DC.  ;D ;D ;D

Obvious, my dear Watson.

Waldschrat

[Graeme Dunbar]

That's interesting - your use of the word anchor in the context of motors

In another place someone was referring to pager-type coreless motors as "clock anchor motors" (klok anker motor). I was wondering how the idiom came about. I'm guessing it is due to the similarity in shape of the eccentric counterweight to a clock anchor escapement (which I presume is so called due to its even closer resemblance to a ship's anchor).

[Hugh Norwood]

Anchor == armature in this context, I think?

[Graeme Dunbar]

Anchor == armature in this context, I think?

Yes - my mistake. I've just looked up electric motors in the German version of Wikipedia.

I got myself lost down a rabbit hole as its seems klok is both clock and bell Dutch. Coreless motors are apparently "bell armature" motors in both Dutch and German and I'd originally mistranslated the Dutch klok anker to clock anchor and not bell armature.

[JulienW]

It's all Greek to me....


:D

[Hobby]

In Graeme's case it was Double Dutch!  ;D

[Graeme Dunbar]

Touche Blair! Well played.

I have a general and occasional fascination with technical terms in other languages. klok anker motor = bell armature motor instead of coreless motor makes sense:

Apart from the specific meaning applied to the rotor of an electric motor - armature:


http://dc1240h7n7gpb.cloudfront.net/wp-content/uploads/1_WG901_EG10.jpg

plus bell:

http://www.oneworldprojects.net/Manifest/Garden/Bells/index.cfm?productID=945

equals:

https://www.motioncontroltips.com/what-are-coreless-dc-motors/

I was hoping to find a video of the armature being wound. I suspect a cunning and very precise form of knitting.  :)

[Graeme Dunbar]

Hi Waldschrat - can you say how many windings/phases does the motor you took apart have please? I can't see the commutator to count the slots. Thanks

Graeme

[Dave Cooper]

If anyone's interested in playing further, I took one out of an old mobile phone the other day. I think the eccentric whizzing around makes it 'tremble' when a certain phone notification is activated. (Incoming call ?).

I applied a 6v supply (4xAA cells) and it got quite hot very quickly. However, at 3v it seemed happy enough...

I intend to use it, with a suitable 'dropper' resistor to power an accessory on the layout where space is tight. It's diameter is about 4mm and length around 10-12mm...I assume from this it's probably coreless ? 

[Graeme Dunbar]

I think it is almost certainly coreless. In the "early days" the only way to get your hands on a small coreless motor was in the form of "pager motors" and find a way of removing the eccentric weight.

[Stefan Krebs]

Dear Greame, and all others,

Apologies for my German background seeping through: in German the armature of an electric motor is the anchor, and of course, I meant armature; I take it that doesn't qualify as typo?  :laugh: :laugh: :laugh:

...and if you take any old pancake motor (Maerklin; Fleischmann, Lima, Trix) apart, you can see where that one came from: the armatures have 3 anchor-shaped poles. To us the 'armature' is the coil only, as in relay-armature (with or without core).

Sorry Greame, I have no intention to unwind the armature. As the wire-windings are self-supporting, i.e. not wound around anything (I'm sure they were during manufacture, but that core is not part of the finished article), I'm confident that any attempt to unwind will end in a mess.
Bear in mind that motor is the diameter of a pencil, i.e. the pictures are a massive magnification! The squares on the paper have a side-length of 1mm, not 1cm, i.e. you're looking at hair-thin (or less!) wires! It appears the metal 'can' is squashed, I can't even slide the armature back in! But you don't see that un-roundness in the pictures!
I have had a look with various (Jeweller's) magnifying glasses, including 20x, and I'm still not sure how the commutation works. And I have been unable to discern the number of poles either!
The 2 plastic pieces with wires attached must be the brush holder (broken, when the can was squashed), and the grey disk joining the copper armature to the shaft are the actual commutator, but you can't actually see individual contact pads.
I suspect the actual brushes and brush springs are lost, as I said, it came like that with an engine in a plastic bag, so I don't know how careful the previous owner was in collecting all bits.  ???

Yes, Dave, I do the same with every old mobile I can get my sweaty little palms on; a cheap source of very small coreless motors, try Ericsson, the smallest I found so far. And yes, of course these are coreless motors like the one pictured. But some very new designs don't use motors anymore to vibrate.   >:(



Cheers
Waldschrat

[Graeme Dunbar]

Many thanks.

My interest is in the derivation of technical terms in different languages (and different countries speaking the same language). It is very easy to think of a word being used in just one context and that might not relate to the original use, so I'm curious as to why the part of a motor that rotates is called the anchor. From an English language perspective it seems to suggest the opposite of the idea of an anchor.

Taking a different concept, in English, electromotive force and potential difference are referred to as voltage, except when dealing with high voltages where "high tension" is used. This seems to reflect the French word for voltage - Tension.  Tension expresses the idea of forces between separated electric charges (as in a capacitor and is a good mental image of the energy stored), whereas a common English mental image of voltage is that of pressure (as in head of water and water/electric current flow). It makes me wonder whether the difference between the notion of "pulling" and "pushing" has any bearing on the way in which electricity is thought about.

[Stefan Krebs]

Dear Greame,

As I said, anchor in German goes back to the shape of the pole on old-style electric motor, like those pancakes have. It is not about the function (anchoring something), but about the shape.

The German 'Spannung' correctly translates to tension, in both English and French; as does 'Strom' to current. Voltage is a creep in English as it refers to the unit (Volt) rather than to the physical effect, i.e. tension.

But why do you charge a capacitor, and not load it when you put a load of electrons on it?  ;D It's not exactly the charge of the light brigade, or is it?  :D

By the bye, this creep of meaning in English is common and drives us foreigners nuts, especially where words of foreign origin are involved. In German, 'Hinterland' is ONLY the area of commercial interaction of a place, e.g. town; but that's not the way it is used in English. Flammable in Latin means 'it can burn', inflammable means 'it can be ignited'; a distinction lost in English.


But we're going off-topic.  :D


Cheers
Stefan

[Frank]

On the other hand ...

In the past we had radios with high tension (90 v plus) and low tension (6v) batteries.  Those were the radios with those funny glass bottles in them.

You charge a capacitor when you put the charge in it.  You also charge your glass when you pour the drink into it.

Oddly, inflammable does not mean it will not burn.

And when you boot a computer you load the bootstrap loader, the simple bit of software that loads the operating system, thereby allowing the computer to pull istelf up by its bootstraps.

Isn't English a wonderful language!

Frank