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4hv.org :: Forums :: Electromagnetic Projectile Accelerators
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Another Coilgun

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Author Post
DerAlbi
Tue Jun 30 2015, 07:08PM
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Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 510
I basically google for "rectangular enameled aluminum wire" and supplier pop up. The problem is however that i need several wire diameters and quite small ones. China only supplies 0.8mm and larger. I would need to start at 0.4 or at least at 0.5mm.

The temperature rise of the coils are of no concern. The copper coils didnt even start to get warm and even with higher losses, less material, and less heat capacity it wont do much.

Just a quick calculation to be sure:
the first coil (the most inefficient one) dissipated around 23J heat. Asumed 90% fillfactor of the aluminum coils there would be 44g aluminum inside the coil. Given 23J of energy.... 0.6°K. No, not important All the focus is back on the IGBTs...

I was in contact with a supplier but those guys do not give technical advice. Every email where you describe your problem is answered by another try so sale stuff to you that you dont need.

Round Al magnet wire probably comes annealed, for best conductivity. Maybe you could reduce it to a nearly square shape and keep the insulation, by drawing it between steel rollers
Do you really think that this would work? i honestly have my doubt. Maybe multiple passes.. but that would put severe stress on the insulation - specially the corners.
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klugesmith
Tue Jun 30 2015, 08:47PM
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Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1478
Please keep us informed.

In case it plants any new ideas, here is the first Al conductor I bought for my big DC electromagnet.

Unfortunately, due to an honest mistake by the vendor, the fill factor is not much more than 50%. Peeling off the obvious layer of plastic film exposes aluminum under a layer of adhesive which is relatively thick, not very sticky, and not easy to remove.

Here is a similar thing I have been watching on ebay.

Aluminum Strip Sheet Crafts Hobbies Trim ETC 15/16x .006 18 LB
In the metals trade, you would ask for for "aluminum coil". Maybe slit it to different widths to vary the turns count from coil to coil, and use thin sticky or unsticky tape (or spray paint) for insulation. Magnetic recording tape comes to mind.

Beware that some popular non-electrical aluminum alloys have resistivity more than double that of the pure element. That came to my attention after measuring aluminum can metal.
At you can search for Al alloys by electrical resistivity. There are some around 2.7 microohm-cm, and plenty above 5 microohm-cm.
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DerAlbi
Tue Jun 30 2015, 09:14PM
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Location: Dresden, Germany
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One manufacturer i was in contact with linked me to a part of their website.
It seems that only very pure aluminium has reasonable electrical properties. (Alloy 1199) I guess that will be expensive. But i could live with it if it wont exceed 40$/kg.
I gave up with this supplier because they didnt really offer technical advice or problem oriented salesmanship. I mean.. yeah. its allways problematic to ask for know-how, but someone professional need to tell me the stuff and how i can do it right. Good coil winding is way over my head. Everything i can think of will just cost so much money and time to even begin to try...
They couldnt even state if their insulation would withstand the deformation if i would decide to make the wire square myself. Thats not so nice. I mean there are insulations out there that do withstand extreme abuse

Those alumimium strips.. yeahhh.. the problem is that i cant think of a reasonable suplier. i mean.. i would need 8µm thickness, 12.5µm thickness and so on. all that with insulation thats much thinner than this to have reasonable fill factor. i dont see that happening. Its also a problem with manufacturing a coil from such a thin material. 1) how to contact the material (the inner winding) and 2 how to make sure a little dust corn does not rip though the metal. 3) is such coil not quite capacitive? Not sure. maybe not.
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klugesmith
Tue Jun 30 2015, 09:27PM
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Location: Los Altos, California
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I don't think capacitance will be significant at coilgun time scale.
But have never (yet) made any electrical measurement on any coil of aluminum wire or sheet.

Here is one clean way to deal with the inside connection of a coiled strip.


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DerAlbi
Tue Jun 30 2015, 09:44PM
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Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
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Awwww i just tried that with paper But my conclusion was: want to see that folding with 8µm foil I am sure i would rip that apart.
However is just found that there are aluminum foils available down to 4µm.
Let me see and double check.
my 0.4mm coil would correspondent to 9µm,
my 1.25mm coil would be made out of 73µm.
While insulating the latter one would be no problem without sacrificing the fill factor the early foils are problematic. the surface would need to be chemical passivated. But there is nearly no room left for epoxy or whatever. hmmmh. ok. i will investigate that for the moment. Lets see if i can find someone who make pure aluminum foil with custom thickness and 2cm width.
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Signification
Tue Jun 30 2015, 10:52PM
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Location: Amite, La.
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OK, there are some nice packaged coilguns for sale ($1000.00 ea)...who is going to buy one and why?
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DerAlbi
Tue Jun 30 2015, 10:59PM
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Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 510
Hmmh? What? Where? who?
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Ash Small
Tue Jun 30 2015, 11:10PM
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Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4118
klugesmith wrote ...

Good discussion of fill factor and Al vs. Cu. Where do you get Al magnet wire? Where do you get square Al wire?
Don't forget that the Al coils will have a greater temperature rise per shot.

[edit]Round Al magnet wire probably comes annealed, for best conductivity. Maybe you could reduce it to a nearly square shape and keep the insulation, by drawing it between steel rollers (as opposed to ordinary wire drawing ). Also look into DIY application of insulating paint onto inexpensive plain wire. Help, somebody please stop me before I edit again! The Ring Lord company has square & round anodized aluminum wire , and we know that some vendors make Al magnet wire insulated by anodize coating instead of organic resin. [/edit]

Your pictures of blown-up IGBT array made me sad, but that's part of the energetic things business.
Does not mean the engineering or manufacturing teams are weak.





If I thought there was a demand for this I'd set up some rollers in my shed, Annealed aluminium (the pure, conductive, 1000 series stuff) is really soft.
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klugesmith
Tue Jun 30 2015, 11:34PM
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Location: Los Altos, California
Posts: 1478
This post is all "thought experiments", from someone with no foil coil experience.

Surely it's easier to get custom widths (you can do that with scissors) than custom thicknesses.
How thick is ordinary household aluminum foil? Shall we measure and report its thickness and sheet resistance?

Do your coil stages have different widths (in direction parallel to axis) as well as different wire gauges?
I couldn't get a common width by reverse-engineering your 9µm and 73µm numbers.
Area ratio between 0.4 mm and 1.25 mm square or round is about 10, but your foil thickness ratio is about 8.
To match the wire areas (square/round), thin foil width is 17.8/14.0 mm and thick foil width is 21.4/16.8 mm.

Try this on for size, assuming 20 mm coil width, rectangular conductors, and no axial or radial insulation thickness.
One layer of 0.5mm wire takes 40 turns, and has radial thickness of 0.5 mm.
25µm x 10mm foil matches the cross-sectional area.
Two 20-turn coils, in series like those in my picture, makes 20 mm width (along axis) and 0.5 mm thickness.

Now suppose we want to match a coil of 1 mm wire, with 20 turns per layer.
Use the same 25µm x 10mm foil, stacking 4 metal layers between each insulating layer.
That gives you a "stranded" 100µm x 10mm foil.
Two 10-turn coils of that, in series, fills 20 mm width and 1.0 mm thickness.

Want to go thinner? Slit the 25µm foil to 5 mm wide and stack four sub-coils within the 20 mm space.
56 turns (14 per coil) matches the turns and dimensions of 1 layer of 0.3535 mm square wire.

Now it might be more practical to start with much thicker aluminum strip material,
and make your low-N coils with that. Use Al or Cu wire for the high-N coils.
If you tell us your approximate ID, OD, and width values, my unhealthy captivation would persist.
I might be able to spare some 125-um-thick low-resistivity sheet from the larger of my electromagnet rolls.
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DerAlbi
Wed Jul 01 2015, 12:20AM
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Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 510
I just calculated it like that: sheet thickness = (od-id)/(2*N) with N being the number of turns in my 0.4mm coil or my 1.25mm coil respectively.

I dont really believe that that subcoil priciple works out. the need to make the layer changes are problematic. Its hard to manufacture and preventing short circuits requires insulation that survives sharp bends.
You basically transform the problem into using flat aluminum wire.
Thinking about that i have constantly in mind that i dont even get the usual layer change reproduceable correct. hmmmh

Edit:
i just read about foil coils.
a) their capacitance is considerably worse than wire wound coils. but its true that this might not be a problem. (the fast coils 100kHz+ are low inductance anyway. resulting in high SFR)
b) the AC resistance is extremely bad. The non uniform radial field component creates eddy currents within the coil itself. therefore the foil is not utilized completely.
c) manufacturing is extremely hard. examples used 6um insulation foil that was larger than the conductor sheet itself. cutting the indurcotrs to the right shape leads to short circuits. even if you get the conductor cut correctly, the heat of the cutting burns the insulator enough that its conductive and will fail over time.
d) however it was stated that the inductors are extremely robust and stable
e) it was stated that its possible to passivate the aluminium (oxide layer) and then just use epoxy to stabilize the turns.

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DerAlbi
Wed Jul 01 2015, 09:09AM
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Location: Dresden, Germany
Posts: 510
Small update: i contacted several companies that supply aluminium strips.
It seems that pure aluminum is quite rare and the best you can get is Alloy 1050a which would provide 77% of the conductivity compared to round copper wire. In relation to that: pure Aluminum would provide 83% of the original conductivity. Its hard to loose those %.. but if its the only way.
Its to be determined, if custom thicknesses (like 8µm, 12µm, 16µm, 24µm and 30µm) are possible.

But i have to say: i just love the german companies. Everyone you write you get an answer like "no sry dont have that, but buy this, this and that, its awsome for sure". German companys: "give us more specs, specs, specs! We want to deliver the right thing and the right thing only!". Thats problem oriented salesmanship. But the price will be high i hope i can provide shocking numbers later on Well.. what is shocking after hearing 880$/kg.. lets see

Btw: i do like the interaction with you guys. i know i am a stubbern kid... but i like the challange to explain myself and why i do it my way.
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Dr. Slack
Wed Jul 01 2015, 11:05AM
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Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1564
Random thoughts about getting the fill factor of alli windings up

If you construct windings from foil, they should be as thick and narrow as possible, so that the insulation overhead as a fraction of thickness is small. Insulation could be one or several layers of cling film / saran wrap, so ideally the strip needs to be >>10x that thickness. Narrow sounds like it should reduce the increase in RF resistivity due to current crowding to the edges, though I don't have a feel for the importance of this factor at the risetimes used in a coilgun.

Their width should be as uniform as possible, so that edge to edge tolerances don't waste valuable width. This also suggests they should be wide, so that edge wastage is small compared to their width, conflicting with the narrow and thick requirement above. What that means is you can't optimise your way out of trouble, you just have to keep insulation thin, and edges neat and close.

You could make conductor from multiple thickness of cooking foil, narrow strips layed on top of each other, or folded from a wider strip, to get the thickness up. However, cooking foil has very energy intensive multiple rolling stages during manufacture, and I guarrantee that the alloy and heat treatment will be to minimise rolling costs rather than maximise conductivity. It's worth measuring the conductivity of some kitchen foil, you might get lucky.

If you start with round wire, you can improve the packing fraction a bit with a single vertical flattening operation, even if you don't go all the way to square for 100% fill factor, it might be kinder to existing insulation as well.

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Ash Small
Wed Jul 01 2015, 12:08PM
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Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4118
From what I know about this subject, kitchen foil tends to be ~99% 'pure', as this is more malleable than alloys. It's also good for conduction.

I did measure the resistance once for a capacitor.

Surely there comes a point where thinner, insulated sections become advantageous due to skin effects?

Pure aluminium sheet is available in many thicknesses, and can be cut with a knife, if you know what you are doing.

Foil can be folded lengthways to obtain the correct thickness, it just needs rolling flat.

There are several different thicknesses available in most supermarkets, from thin 'wrapping foil' to heavy duty 'turkey foil'. Thickness also varies between manufacturers.
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DerAlbi
Wed Jul 01 2015, 03:36PM
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Location: Dresden, Germany
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Kitchenfoil is around 10µm thick. That order of magnitude is ok, but the material... i dont know. Not only that 30m is by far not enough, but even if the purity was 99%, it would be a very bad conductor. (Electrical grade starts at 99.5% (1050a alloy), and that allready is borderline usable)

In order to make propper coils one needs proper material. i dont think any improvised solution will fit into a high performance coilgun.
I mean.. in order to get my efficiency that high, i had to do everything right. I cant become sloppy at the last steps.

Insulation: i honestly think that for very thin sheets i can passivate the aluminum with an oxide layer the chemical way.. i mean.. the insulation has to withstand 3V max per layer and basically no mechanical stress/relative movement. Very thin glue/epoxy dissolved in acetone with the acetone boiled of should give a stable and long lasting mechanical solution.
As the aluminum gets thicker, the insulation can become more relaxed and thicker. The very thin coils will suffer from insulation induced bad fill factor, but those coils suck anyway. Maybe i make the wirst 2 coils from round copper and thats it.
I dont think that it will benefit the fill factor if i use 2 different thicknesses in order to get another thickness. Its much better just to have the right foil available.
I am working on that. Just wish me luch. Many have plainly said "no can do", the foreign companies said "no, but buy that, its awesome" - meaning some steel product.. and one company sound pretty promising.
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hen918
Wed Jul 01 2015, 05:05PM
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Location: Alfreton, UK
Posts: 399
DerAlbi wrote ...

Kitchenfoil is around 10µm thick. That order of magnitude is ok, but the material... i dont know. Not only that 30m is by far not enough, but even if the purity was 99%, it would be a very bad conductor. (Electrical grade starts at 99.5% (1050a alloy), and that allready is borderline usable)

In order to make propper coils one needs proper material. i dont think any improvised solution will fit into a high performance coilgun.
I mean.. in order to get my efficiency that high, i had to do everything right. I cant become sloppy at the last steps.

Insulation: i honestly think that for very thin sheets i can passivate the aluminum with an oxide layer the chemical way.. i mean.. the insulation has to withstand 3V max per layer and basically no mechanical stress/relative movement. Very thin glue/epoxy dissolved in acetone with the acetone boiled of should give a stable and long lasting mechanical solution.
As the aluminum gets thicker, the insulation can become more relaxed and thicker. The very thin coils will suffer from insulation induced bad fill factor, but those coils suck anyway. Maybe i make the wirst 2 coils from round copper and thats it.
I dont think that it will benefit the fill factor if i use 2 different thicknesses in order to get another thickness. Its much better just to have the right foil available.
I am working on that. Just wish me luch. Many have plainly said "no can do", the foreign companies said "no, but buy that, its awesome" - meaning some steel product.. and one company sound pretty promising.


I would recommend ABS dissolved in acetone, done properly a very nice very thin layer can be produced.
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Signification
Wed Jul 01 2015, 07:47PM
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What about square Cu TUBING?
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DerAlbi
Wed Jul 01 2015, 07:51PM
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Do you really suggest, that i dissolve my childhood Lego?
No, seriously: thin layer ok, but is it as rigid as epoxy?
Hmmh. actually quite an important question... if rigidity comes from the glue material or the fact that the metal is glued together.

Sry, cant follow the tube-idea.
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hen918
Wed Jul 01 2015, 09:11PM
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DerAlbi wrote ...

Do you really suggest, that i dissolve my childhood Lego?
No, seriously: thin layer ok, but is it as rigid as epoxy?
Hmmh. actually quite an important question... if rigidity comes from the glue material or the fact that the metal is glued together.

Sry, cant follow the tube-idea.


Well, the rigidity of epoxy largely depends on whether ratio of hardener to resin is correct. If it is perfect, I don't think ABS will be as rigid, however I think your second point is important, when it is all glued together, the overall rigidity will be about equal.
An important factor will be how well it sticks Al together, that I don't know, although you would coat the whole coil in it afterwards, to keep it solid anyway.
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Ash Small
Wed Jul 01 2015, 09:17PM
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If you use a slow hardener you'll have up to an hour, depending on ambient temperature, to wind it, and get it as perfect as you can.

I'll try to find a link to some tests done here with it.
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DerAlbi
Wed Jul 01 2015, 09:38PM
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Naaah.. i think the trick with epoxy is the acetone.
You mix it in and keep the mixed epoxy simply stored. The acetone not only make the mixture thinner, it also inhibits the hardener to work. Then, when you dispense the epoxy, you heat it up for a short time, evaporate the acetone and the mixture will react and harden inside the coil. That should give a good an relieable thin coating that in the end will become rigid.
I do however not think that an outside coating of epoxy will improve the coil structure..

(Maybe there is something else than acetone that works the same way but wont cause the environment to die.. but you ge tthe point.)

Edit: enameled wire can come with a heat bondable polyurethane coating. maybe thats also an option since its simply made for that purpose.
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DerAlbi
Fri Jul 03 2015, 06:39PM
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Hmmmh. News from alu foil supplier: there is no economical way to produce the foils in specific thicknesses. there are pretty much some standard thicknesses out there and thats it. I also learned that insulating aluminium foil issnt that easy. The aluminium oxide is birddle and unrelieable when thin. Therefore its better to go with an insulation foil... that would end up quite thick and with bad fill factor.

Back to square one: using round aluminium wire, winding the coil a little longer and then apply pressure untill the wires are compressed?
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DerAlbi
Wed Jul 15 2015, 06:15PM
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Coils: i finally found a supplier (within Germany) who supplies square aluminium wire. The thinner wire is quite expensive (like 60€/kg) but that is reasonable. The explaination is that the machines produce Length/Time and not Weight/Time. So thicker wire will cost much much less in the end (you pay for time). I think the overall price for all coils will be ok. Now the problem is to get sample quantities like 250g... (minimum order quantity is 60kg)
I want to try to eliminate the need for thin wire. I would allready need to start with 0.3mm square wire.. but i am using 0.4mm instead. Maybe i also can get rid of the 0.4mm wire and use 0.5mm wire instead. I could compensate the wrong diameter with PWMing the Coils... that puts much more stress on the IGBTs. This not only adds more turn-off losses, but it also adds turn-on losses. And my diodes are not fast types. that would suck. But the expensive wire...

IGBTs:
i finally experienced my first 650Vdc shock between left & right hand Survived. I never stop before it happens.
I was testing my active clamping circuit above with the right TVS diodes. Unfortunately i did not have any luck with my ordered parts because the voltage rating is way off. My IGBTs are 650V rated inside a 600V environment. I managed to set the clamping voltage to 660V but not inside the specified range. I need to order different TVS diodes again. The temperature dependence of the TVS didoes are around 30V. That leaves a quite narrow range where everything works. Managable but not nice. (Temperature range is limited anyway. Electrolyte capacitors wont work at low temps like 0°C.. the ESR rises to shitty levels.. lol.. which heats up the caps )
What is funny is that i actually used spare IGBTs that were only 600V rated. However they were totally fine with >700V between emitter and collector I know that this is to be expected as long as the IGBT is cold.. still... it was a tense moment..

Projectile positioning:
The second version of the laser distance sensor is finished. I works somehow and it was fun to develop and build. However it is not suited for use as a relieable positioning system. The projectile does not reflect the laser in a relieable and predictable way. The solution would be to add some optics to the light receiving photodiodes.
I have however a quite good plan to make a sensor system based on eddy current sensing. That should perform as good as light traps, (Which did not perform good and was a computational nightmare ) Still: when it works predictably bad, it works good.

Hmmh. Nothing else to say.
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DerAlbi
Mon Aug 17 2015, 11:43PM
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Over a moth of silence.. but i was working hard on the project. It was quite some conceptional work, simulation effort and a PCB design nightmare.
The developed system is a whole 3D-PCB design that features a main control PCB with sensor evaluation, a long connector board for all sensors and the sensor PCBs themselfes. All layouts are desgned to be 4 layer 0.5mm thick PCBs. I also upgraded the microcontroller to a floating point capable version. I hope that helps the sensor evaluation.
The sensors are now made out of PCB-coils which are connected in series. The sensor coils work inside a high frequency series RLC-circuit at resonance. In the presence of the projectile a sensor coil will change its inductance, (since its short circuited) and the RLC circuit shows a phase-change between voltage and current.
At least in theory.
Practical issues are that i dont know how the barrel will change the inductance of the sensors and i also dont know the influence of the main coils (through coupling).
What also sucks is basically the inflexible concept. The whole thing is designed to be assembled and then just work out of the box.
The build is currently designed to host a small number of coils. Just a proof of concept so to say.

Here is a paper model of the designed stuff...


Concerning the aluminium wire for the coils, there is not much going on. Hard problems.
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BigBad
Fri Aug 21 2015, 03:31AM
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DerAlbi wrote ...

But i found only chinese suppliers which ship in multiples of 10kg or if the wire is not in stock the minimum order quantitiy is 500kg
Since this seems currently unreachable i will continue to use round copper wire.. which will give better efficiency but tripples the weight.

How do you figure triple? Copper should be more like only 30% heavier- that's the advantage on overhead lines where they use aluminium. Don't forget that copper is a lot more conductive than aluminium, so you can use much thinner, copper wire and still get the same impedance.
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DerAlbi
Fri Aug 21 2015, 09:24AM
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Hmmh. Here some numbers
Alumin(i)um density: 2.7g/cm³
Copper density: 8.9g/cm³

For the same volume (and yes, the coil gemoetry remains constant) i have and advantage of factor 3.3.
However: the volume fill factor of round copper is only pi/4=78% (confirmed! by experiement, 77% or something). if the aluminium were 100% of the coil geometry the factor shrinks to 2.6. so roughly 3
(yes, your doubt was correct, but the aluminium fill factor wont be 100%, so 3 is still a goos approximation)

Thinner copper wire:
No Again numbers:
Aluminium conductivity over density: 35e6S/m / 2.7g/m³
Copper conductivity over density: 58e6S/m / 8.7g/cm³

You find that Aluminium has actually better conductivity per weight than copper. So with weight and efficiency in mind you allways can use the same mass of aluminium and end up with lower resistance. The other way around, to use less copper to meet the weight of Aluminium, will increase resistance more than using aluminium from the start.
And in my case thats worth the trouble and within technical reasoning.
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BigBad
Thu Sep 03 2015, 10:10PM
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 599
It's better, but not 3 times better.
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DerAlbi
Tue Sep 29 2015, 12:48AM
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 510
Well... to break the long lasting silence, i post some photos of some progress....
i was not really inactive, but designing all the pcbs was hard and there was some trouble with the manufacturer. Additional i relocated myself to another, much better flat where i am about to have a much better working area and actually some place left for living. that quite an upgrade compared to before.

So back to coilguns: I assembled the new main contoller. I just have applied voltage and the current is reasonable.
Top Side: (excuse the crudety of the images. since i am still bussy moving all my stuff i didnt find my camera yet - dont know which box ^_^)



Bottom Side:


Its not fully assembled. One IC is missing since i ordered the wrong part -.- 74hc126 instead of 74hc125. And there are some capacitors and 0R-Jumpers missing.. they will added when the software is ready to use the hardware features.

I tried my best here to make the controller really small and fitting perfectly to the barrel construction. That called for QFN-Packages. Both for the main processor and the guard-µC..


Yeah.. i also bought a cheap usb microscope. It sucks. But it does the job.
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DerAlbi
Wed Oct 07 2015, 01:47PM
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 510
Got the sensor system working. It seems promising. Its not too noisy and the amplitude is reasonable.
The eddy current sensor system is affected by the presence of the accelerations coils but it can be calibrated away. i could also try to use higher sensing frequency to increase the amplitude. but thats for later.
Here is a print of the sensor output voltage. Sensing frequency is around 5MHz. I just pushed the projectile in an out with my fingers.

The sensor system is susceptible to the coil switching. i can get glitches on the sensor voltage by applying a kHz-Squarewave to an acceleration coil. however those glitches are only caused by a decision previously made [about coil switching] and the glitch only lasts for 1..2µs so plenty of time for the sensor to recover until it must work again for the next decision.
I really like it. if i would do another revision (not planed right now), i would maybe add some opamp to increase the signal strength.
The noise (line thickness) you see is around 50mVpp while the sensor amplitude is 0.2V.
As far as i know i am the first one using this concept in a coilgun as replacement for light traps. it will never need cleaning, adjustment or any other form of attention.
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Zero
Mon Oct 26 2015, 10:51AM
Registered Member #3588
Joined: Sat Jan 08 2011, 11:19AM
Location:
Posts: 36
Video? :>
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DerAlbi
Mon Oct 26 2015, 04:50PM
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 510
No.. Sry, there is no point in making a fancy show. This thread is about technical coolness, not about the typical Youtube-Coilgun stuff where some 2%-eff-guns shoot at stuff that would even break if you just drop it on the floor And i cant compete with all the kJ-guns in the titles too, since i havent even that much, even if i beat most of them in projectile energy.

But its time to give another update...
I experienced quite some technical setback here. My sensors that initially worked so good are now quite useless due to some unexpected parasitic issue. One eddy current sensor worked fine, multiple sensors in series dont work. My setup is so shitty the the sensor coils have a (parallel) self resonant frequency at exactly the frequency that i wanted to use for sensing the projectile. This forces me to switch to way lower sensing frequencies where i just dont get the strong sensor readout that i have shown above.
It was not designed for such operations.

I will try eliminate the obvious mistakes i made as good as i can patch them within the current setup. If i can confirm that the system has still potential then its time for another small redesign.
I am currently also a bit slower on the thing. I simply run out of budget.
I hate it that crowdfunding refuses Coilguns. I would actually need it. Damn. Bringing this to a commercial level is really possible. i assembled the whole accelerator in under 20 minutes and i leaned that small changes would make it even easier to assemble. Ive come so far But yeah.. its normal. The last 10% are as hard as the first 90%. It holds unconditionally true.. fact of life.
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