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modified 7 years ago

Question about homemade inductors

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00:53:42

I wanna make a 1H (I know, it’s big) inductor for use at 60Hz with an equivalent series resistance of no more than 50ohms and that’s capable of handling 5W dissipation without overheating using only common household materials for a core (like nails and bolts and screws and stuff). How should I do it? How much wire will I need? What AWG should the wire be? I’d preferably like a design with a minimum number of turns because I’m lazy.

published 7 years ago

7 years ago

How much wire will I need? A mile? A thousand feet? A hundred feet? I don’t think I wanna wrap a one mile length of wire. I do know that wire tends to come in spools, so they might already have a pretty high inductance and are simply in need of a core.

7 years ago

If you could powder the nails, you can pack more iron ( higher density). You need a lathe for that, or can get it from lathe workshops. And make a paste with glue, to form an iron core, the glue keeps the eddy current Down., you have ti get your hands dirty.

7 years ago

I thought it had to take 5 amps and have a resistance (not lumped Z) of 50 ohms?

7 years ago

@zorgrian don' t really mean to recycle ♻ or upcycle, have you seen the price of a reel of enameled wire recently?! Or the price efficient light bulbes!!?

7 years ago

Ok wrong... It must be able to dissipate 5 Watts

7 years ago

Was just going to mention that, be careful what materials are used, temprature has a habbit of building up. It is brst to use cement to glue the nails or iron dust. Ready cement you can buy from pound shops in small containers.

7 years ago

And the second one you make is going to be better than the first one.

7 years ago

There's nothing wrong with recycling

7 years ago

Especially if you live in the united States of Trumperica

7 years ago

Or EU which both prevent importation of base metals at reasonable rates. This directly affects making electronic components such as transformers

7 years ago

One £$¥€ shops

7 years ago

Unfortunately, we allow our world to be controlled by a casino, called the stock exchange

7 years ago

5000 turns of wire on a 100mm air former (plastic plumbing tube) about 200 mm high will be 1H

7 years ago

But, with thin wire like this that you could recycle from old speaker voice coil, motor or other device, may wind up hot!

7 years ago

This is safer than nails

7 years ago

A 500 ft spool of #12 wire can cost $55. It has dc resistance of .794 ohm. Any smaller gauge comes on 100ft spool. I might have a half spool or so (250 ft), maybe I can figure out how to measure its inductance. Can you give more specs like the anticipated voltage drop and amperage? What bulb will this be for?

7 years ago

@jason, what is the 1H inductor intended for?

7 years ago

@rich you can neasure inductance the easy way or the hard way, the easy wsy is less accurate. http://everycircuit.com/circuit/6055556422041600

7 years ago

@zorgrian casino style economy, i hadn' t thought of that, it is exactly that. All i meant ti say. I am not a recyling freak. Otherwise there nothing wrong with recycling, but better policy would be not ti make the waste in the first place, then don' t have to spend even more energy recyling. 5000 turns might be more than you can imagine, it is a lot. An iron core will hipefully reduce that by quite a lot, helping lower resistance, and less pain in the wrist.

7 years ago

@jason am sire you know what uou do, but i have worked with inductors,. They can be very dsngerous like @zorgrian ssid too. Specially ehen you turn them off, they arr most dangerous,, really high voltagrs and currents are produced. Old tv,s even after they were switch off and unplugged, the tube power supply stored enough energy, high enough to knock life out of someone. They could produce 10, 30 centimeter sparks, high power, very nasty.

7 years ago

I intend this coil to be used for a mains voltage gas discharge tube with air being the gas used. Because of the DC resistance and reactive impedance it will be ok to short the electrodes to get the spark started. I understand about the switching off a coil can be dangerous problem, but what would be the best way to deal with it? Narrow spark gap (few millimeters) to discharge when high voltage strikes? Few hundred ohm resistor in parallel? Let the switch act as a spark gap to discharge the coil (I’ll have to open it slowly so as to let a spark form before the gap becomes big enough to force the spark to form somewhere more dangerous)? At any moment it shouldn’t have more than half an amp going through it, although that might actually be a lot.

7 years ago

You might get resonating, the inductor will have capacitsnce. Sprcially if you wind it loosly by hand. 5W,,,,,0.5A,,,,,,???!

7 years ago

@jason9, half an amp is 12.5W at 50 Ohm.

7 years ago

1 henry on 120v will be 1/3 amp. Then it will be put in series with the tube, so it will be less amps and less voltage drop. 1 henry is much more than 50 ohms impedance at 120v 60hz.

7 years ago

50 Ohm was a maximum requirement from jason

7 years ago

130mH has the impedance of 50 ohm at 60 hz with 2.4 amps. Maybe the primary of a doorbell transformer or a relay coil would work.

7 years ago

I think he ment 50 ohm dc resistance,. He didn' t specify any voltage, just 60Hz, 1H, 50ohm series resistance .and 5W..

7 years ago

Keep up rich, this is a matter of national security (we don't say which nation, naturally)

7 years ago

Thee stated specification is "with an equivalent series resistance of no more than 50ohms"

7 years ago

This strongly implies, yet is not implicit, that we are talking about thee non reactive Z component.

7 years ago

I must reinforce, I am not in favor of the nail bomb method

7 years ago

Unless, this device is to be used to vaporise politicians

7 years ago

60 Hz means he is not here.

7 years ago

XL= 600* pi. It will make a good resonator, cause of pi.. If it is not dipped in wax. The vibration at 60hz. Could destroy the inductor.the vibrations will also help heat rise. Whixh should help to melt the nails.

7 years ago

'He' is in the land of Trump Pence

7 years ago

When the nails melt, the induced force will propel liquid metal at the old terminator

7 years ago

2 in one... A simple liquid metal terminator reducing mechanism + added light from rapidly disappearance of everything

7 years ago

OK... Steel (nails glued together relative AK approx 100) so, a diameter of 100mm 150 windings of 2.5mm insulated single core mains wire. This should produce the desired 1H inductor. The nails must be glued using epoxy, two part glue.

7 years ago

Ak = al

7 years ago

Well Jason worried the esr could exceed 50 ohms, so having a .6 ohms esr is a major difference. I would assume this brilliant middle school kid hasn't received formal training in a electronic curriculum, I don't think he read chapter 6 last week in anticipation for his exam this week. So its not impossible for him to think esr = z, they are both AC measurements, unless otherwise specified. Just wanted to throw it out to him.

7 years ago

Maybe he has been arrested.

7 years ago

So zorgians setup: 618 ft of #10 solid with 0.617 ohms dc resistance, that's going to cost around $120 for a electrical supply shop to cut that, some times they charge you 2x if they are in a bad mood so that could be $240 worst case. Any cheaper ideas? 5 watts not 500.

7 years ago

Clarification on specifications: 60Hz at 120V RMS/170V peak, no more than 50 ohms DC resistance, and capable of handling a current of 500mA RMS/707mA peak. Forget the 5W thing, I probably messed up my calculations when calculating that.

7 years ago

If the current specification seems too high, then just call it margin of error.

7 years ago

Error in the margin, or margin in error?!

7 years ago

UM.... well that does change it a bit you could use really thin wire and upcycle it from some dead electrodomestic item at your local tip (that means trash center an AmEnglish) Alternatively, ask your leader Donald Trump, to provide access for metal imports to USA and you will wind up with reasonable prices again

7 years ago

Will you call a spade a spade? or use some error of margin = NASA?

7 years ago

@kiani, margin of error in specifications is when you use a component with specifications that are higher than necessary for what you’re using it for so that if you mess up your calculations too much or something and end up overloading it, it can still take the extra power without being destroyed. That way, there is some room to make some small errors without anything bad happening.

7 years ago

Btw, for a core I just realized I have metal stakes for holding things in the ground and I’m pretty sure they’re solid steel. That would probably boost the inductance significantly.

7 years ago

Do you know what a magnetic hysteresis is?

7 years ago

Do steel rods, remain magnetised after rubbing them on a magnet?!

7 years ago

Everything passes with time, especially lunchtime

7 years ago

Rubbing two sticks together does a similar act. Neither sticks nor stones may break my bones but words will always help me

7 years ago

Isn’t magnetic hysteresis when a ferromagnet retains some of the magnetic field even after it is switched off? And because of that it can lead to hysteresis losses in inductors? Does it have anything to do with saturation?

7 years ago

Do they use pure iron for the core?! Why?!

7 years ago

You mean my metal stakes? As far as I know they’re pure steel all the way through. Maybe not exactly high quality steel, but they’re still steel, which has a relative magnetic permeability of about 100. Also, I tried rubbing a magnet on them and measuring the magnetism of it before and after (apparently modern mobile devices have magnetometers) and it definitely retained some of the magnetic field afterwards. When there was no stake, it measured 40uT (perhaps the magnetism of the Earth or the magnetism of my iPad or something), when there was a stake near my iPad it measured 100uT (I think the ferromagnetism boosts the field or something), and after I magnetized the stake it read at over 500uT when near my iPad. The magnet itself measured at over 4000uT (4mT).

7 years ago

In transformers they use pure iron, cause they don' t hold on to magnetism. Otherwise as the voltage swings the magnetic field is free to swing without the metal core trying to hold on to its polarity. If the core becomes permenat magnet ( north pole and south) when the coil wants to swing and contineously chane the north and south, will try to resist that. But pure iron eventhough becomes magnetised, but doesn' t retain and hold on to it. That msked steel unsuitsble.

7 years ago

Yes, but it should still be better than nothing.

7 years ago

Don' t know what effect iy might hsve on the inductsnce,. Ehen i needed to build s demagnetiser, i needed 500 mH to discharge a capacitor,. I tried everything but in the end i had yo find sn old transformer and use s hsmmer to grntly work the ( E core) flaps loose ( they are purr iron, ) and rrbuild it with new windings,. It was perfect. With good oscillations,. You can experiment with steel and mske just a small inductor and do some tests on it. If msgnetic fild is not sllowed to move freely then you will just have a big resistor. Only with dc resistance. And may be a non linear inductor.

7 years ago

Right, thats correct @kiani, what jason needs is some “soft iron“ so bad nails are the best core material to not have a magnetic hysteresis and many nails avoid the second not wanted effect, “eddy current“ so best the nails have a isolating paint and no electrical contact.

7 years ago

So what should I do? Wrap wire around a box of nails (preferably insulated from each other)? How should I measure inductance? How much wire and how many turns will I need?

7 years ago

You don' t have the right info to calculate the turns, nails flux density hasn't been checked out yet. So yiu are going to do it. By experimentations and measurments. Hoe about cans of besns,. I just checked the tin of marrow fat peas. Looks ideal, seems to be pure iron. It can br filled with nails and then sealed. Spray the nails with paint first so they are idolated ( reducing rddy cuuernt hopefully). Btw. An experiment is not an experiment if it is successful! We do 20 experiments and learn a little each time. And we build knowledge, and sometimes ee learn stuff quite unrelated to what ee set out to find out by the experiment. There is no failed experiments, cause the aim is learning what to do and more importantly what NOT to do. 🔩

7 years ago

If i say “nails“ i just mean core material. So take anything you want, dont know what you have available. Use a waterheater in series, measure its resistance cold and hot, the hot one will be a little above the cold resistance. Make a coil on material of your choice and measure the current in series. Coil, heater and ampmeter. Write down the current you measure. Start with 10 turns or 100, make some calculation and get the inductivity. If you have L and its to low, double the number of turns does increase the inductivity by the factor of 4!!!! So you can get close to your 1 Henry, or you will see you are to far away. Everycircuit will help you to not do too much math.

7 years ago

Lets go, take some core material and do 100 turns, check this http://everycircuit.com/circuit/5479781461393408

7 years ago

OK, so at the risk of treading upon old ground, if you have an iPad, why are you piffling around with steel stakes? Why not buy a toroid core?

7 years ago

I cant buy an iPad

7 years ago

But toroid cores are not expensive

7 years ago

Or... If you don't like toroid core shapes then buy another core

7 years ago

I have an iPad because my parents gave it to me. I didn’t buy it myself. I might be able to get my parents to get me the core, but I’m not sure. They really don’t like spending money. I only have an iPad because right now I can’t live without one and also I only have my current version of iPad (iPad Air 2 I think) because my old one got stolen in a robbery.

7 years ago

What is an iPad?!

7 years ago

Whst you need, and want is a horse 🐴 shoe, . They are made from forged iron ( perfect 👌 for inductors), { i guess they are also made from plastic these dsys), whrn you get one test it with a magnet to see it magnetises whrn adgasent to magnets, but does not retain magnetisem when separated from the magnet. You could even make it into a toroid.

7 years ago

Plus it is a nice thing to have, anyway.

7 years ago

A@jason you arr not trying to get as many 🎃 ( thred reply icon) as possible. Arr you?! It goes yellow after a certain number, i wonder if it changes colour again at some point.

7 years ago

IRON a wonderful material. On fact it is the final product after a star burns out completely and produes all kinds of things until the end of process, only iron is left. The aim of a star production, iron. Specially when it is forged. It is magnificent have a look at it' s Atom configeration. The final producy of the sun. Some is in our blood. An important element in life. Another place you can find this wonderful material is old 🚂 train rails. Pure iron, not steel, which is man made. A determind material. The only matal that can face gold.

7 years ago

Nope, I’m not trying to get as many comments as possible here, but it is an interesting consequence to what is happening here. Btw, an iPas is basically like a mobile computer with a touchscreen instead of keyboard and mouse. I don’t think I have any horse shoes laying around. I think I’ll stick with the metal stake. Also, I’ve decided that mains electricity is way too dangerous for me to be working with without proper training and safety equipment, even if I have a switch to turn off power when reconfiguring the circuit.

7 years ago

Ok use steel and learn the hard way. And after get a horse shoe.

7 years ago

So let us know what AC source you have. What exactly is this “metal stake“ you have. Picture?

7 years ago

Where do I post a picture? I don’t have an imgur account.

7 years ago

My metal stake pretty much just looks like a giant nail. Maybe about half an inch in diameter and maybe a foot or a bit less in length. Btw for AC source my only one is mains power which is way to dangerous.

7 years ago

Haven' t you made that inductor yet?!

7 years ago

Yours stakes are propable already to hard metal, as we said you need soft metal, iron not steel to avoid magnetic hysteresis. Imgur or any other account can be created, even with an iPad. For the AC source, dont you have old heavy transformers from old toys like car racing etc. ?

7 years ago

I haven' t tried this myself, but how about putting a few ( old type) light bulbs in series with the ( 170 peak) mains and take pick a safe enough point.

7 years ago

After 12days and more then 100 comments nothing is going forward. As your manager i would a little annoyed 😁 no im not, but i wonder cuz you wished we shall stayed tuned on this topic and now its cold. Please dont tell us now a boring story why you have no time ... blaaa blaa. Or its a really interessring story!?

7 years ago

Maybe he,s bern extroditrd to mexico over trump,s wall for rubbing nails and stakes.

7 years ago

For safety I’d imagine a 100:1 ratio transformer would be best. I saw a youtuber make a transformer with literally one secondary turn for melting nails and stuff by using the high current. He recommended to never touch it even if it is at safe voltages because it is capable of delivering lethal amounts of current. Of course I’d need a large primary inductance for that to keep the mains power from shorting out through the primary which takes us right back to the beginning.

7 years ago

10:1 is fine. He recommended to not burn your fingers at hot nails. Low voltage transformer can provide high current, but your finger are much higher in resistance then a nail. Ohms law says, V/R=I for a nail 1V / 0.01Ohm = 100A while your fingers are 1000 times higher in resistance. Dont touch with you tongue 😁

7 years ago

This what you watched on video,, are you sure it wasn' t a cocacola advert?!!

7 years ago

Thetr is an easier wsy to melt nails, if you have coal fire 🔥 place just throw your nsils in there, the nrxt day you hsve pure iron, csuse all impurities hsve burnt out. And you csn use a hamner to shape the blob. Of coursr don' t do anything eithout permission fron your parents. Or else they might stop feeding you.

7 years ago

Oh, good.! He has given up on this nail inuctor thing.

7 years ago

Nails... i would start with some iron wire, you know this stuff for binding flowers. Soft iron wire. Tens of pieces few centimeter long maybe with isolation if thin

7 years ago

If I melt steel will it purify into iron?

7 years ago

How will you melt anything like steel if you have already problems to heatup your soldering iron to melt solder (tin lead copper mix)? Think you need another app around chemical things.

7 years ago

Hmm steel you need 6000. Degree centigrad to melt. Steel melting factories have to heat up their furnace for 6 monrh before it is hot enough ready.

7 years ago

Can not get iron from steel in a furnace.just foget abou steel. Ok. Think iron. there must be a broken electric shaver in your houshold. They have a transformer inside.

7 years ago

6000?

7 years ago

Well maybe about 2000 degrees for furnace. Need 6000 if welding or cutting big chunks of steel, to reach 2000 locally fast enough before obsoebtion.

7 years ago

@jason9, thread closed we can remove our bookmarks, right?

7 years ago

Sorry, I haven't been around for a couple days. How should I obtain pure iron? Is it possible for someone like me to do? I know I can melt aluminum with hot coals (I saw a guy on youtube do it) but how do I get iron? I'm thinking I'll have to burn the carbon out of steel which will require melting, but I don't know how to melt steel and if it's stainless steel then it will contain other metals in addition to just iron. How do I get pure iron? Do I have to buy it or is there another way?

7 years ago

In my view, the bestest idea is to get hold of an old transformer. The best pure iron you find has been used to make the transformers. There are a lot of places you can find an old transformer ( i mean the 50 or 60 Hz. Ones) . They are everywhere. Everything that works with mains has a transformer. The nee equipments have smps ( switch mode psu) . Theier transformers are not suitable for low frequency, they use powder core materials,. look for old transformers. The best iron already purified is there.

7 years ago

Notice bookmarks getting fewer...

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