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**blackchisel97** · 04-13-2011, 11:23 PM

Originally posted by dR-Green View Post

Hi all, I've been wondering how big is too big to make the coil for a Bedini machine? Both length and thickness of wire, or weight if anyone knows. The fact that people sell spools of wire by weight rather than length confuses matters, so it would be good to know if it's possible to just use a whole spool of wire rather than having to measure it because it can't be too long? Or does it not matter if it's a pretty huge length, if you used 1KG of 22 SWG for just one winding for example?

I also have 500g of 15 AWG wire here that I bought to make a Tesla coil, but I've been wondering lately whether to stick a transistor on it and hook it up to the SG to see what happens. Is this too thick? Is it worth buying more and using them to make 6-filar power coils for example, or is it too much? How about 6 x 1KG 15 AWG wires?

I've been concerned whether the 250g available from Maplin or 500g from RS [edit] of "recommended size wire" that I'm using were long enough for the coils because I had absolutely no idea how long that is, so yesterday I had the idea to look on ebay for wire, and there's a guy selling 1KG spools of wire for a pretty good price so that's why I ask about the 1KG spools (and also he states approximate lengths. Which btw RS have changed from selling by weight to length since I bought the wire from them and now the 500g of wire that I have is claimed to be 200m on the product page, which doesn't match the numbers the guy on ebay gives, so I still have no idea how weight relates to length). They cost less than 2 x 500g spools, so I thought if the bigger the better then I'll go with the relatively cheaper 1KG spools and make huge coils

So any words of wisdom on this matter would be appreciated

dR-Green I can share something based on my experience. The thickest wire I've been using for all my builds was AWG#18. As far as the length goes I never went under 100 feet. I found best deal when buying large 9-11lb spools. There is a chart - Engineering Data which helps to find needed values. And another one - MAGNET WIRE 12 to 19

As an example; AWG 18 which is 0.0393" or 1mm thick is rated at 1.21A. 70m or 208.3' weights 500g or 0.5kg. Has 6.9Ohms per 1000' or 22.63Ohms per 1000m (1km).
I have used those charts to easily determine how much wire I need to make a coil which will have a certain resistance or if given spool will yeld enough wire for my project. While it may seem annoying that different sellers operate in different spools sizes, weight etc. all you need to do is to calculate the unit price eg. how much will cost me a 100 feet and compare data among sellers.

I hope you'll find this helpful

Vtech

**dR-Green** · 04-17-2011, 07:31 PM

Thanks for the reply and links. It was from your solid state video I saw the 18 AWG being used which first got me thinking about bigger wires. Is there a maximum length of wire recommended for a coil though? And do you use 18 AWG just because you like it, or would any bigger not work?

I should think I wouldn't have any problems with the wire being too short from a 1KG spool, but could I use that whole spool as 1 length of wire, or would I need to cut it shorter?

Is there any practical purpose or application for knowing the length of the wire or making it a certain length, besides to know that your coil won't be too small?

Thanks

**blackchisel97** · 04-17-2011, 08:13 PM

Originally posted by dR-Green View Post

Thanks for the reply and links. It was from your solid state video I saw the 18 AWG being used which first got me thinking about bigger wires. Is there a maximum length of wire recommended for a coil though? And do you use 18 AWG just because you like it, or would any bigger not work?

I should think I wouldn't have any problems with the wire being too short from a 1KG spool, but could I use that whole spool as 1 length of wire, or would I need to cut it shorter?

Is there any practical purpose or application for knowing the length of the wire or making it a certain length, besides to know that your coil won't be too small?

Thanks

@dR-Green

Coil should have certain impedance in circuit to match the impedance of charging battery. Not to confuse with physical resistance of copper wire.
While you can make your spool bigger by using 150 or more feet of each wire there is no benefit from such. I found 100' a minimum required to work but again, you can use 120 or 150 and get the same results.
I found #18 being the thickest you can employ in those circuits without having problems.
Keeping those in mind you can imagine expanding it. If I may use analogy from nature: Imagine a tree with branches collecting and passing into the main trunk. You want as many of the branches as possible to collect but also, you want them to be of certain size. Not too long and not too thin but not too thick either so the flow isn't obstructed or delayed. In other words, as efficient as possible. Multiple branches are better than just a few.
Coil windings are the branches and trunk is the bus terminal where all diodes meet.
When working with iron core SSG keep ID of the spool not larger than 3/4".
In case of NeFeB magnets ID should be smaller than that.

Vtech

**Neight** · 04-18-2011, 06:28 AM

I actually just learned about this today

for what i am doing with my build, I couldn't have more than 4-6 ohms resistance from my power coil. I measured what i had and wound up with about 7.5 ohms. I am going to unwind a bit of my coil and test until i get down below 5.5 or so and see if that doesn't fix my current problem (coil self oscillating/motor not spinning). It will depend on gauge and impedance as blackchisel97 pointed out, but apparently there is indeed a too long

hope this helps (nice to be able to put info in instead of just asking questions!)
N8

**dR-Green** · 04-19-2011, 12:28 AM

Originally posted by blackchisel97 View Post

While you can make your spool bigger by using 150 or more feet of each wire there is no benefit from such. I found 100' a minimum required to work but again, you can use 120 or 150 and get the same results.
I found #18 being the thickest you can employ in those circuits without having problems.

Ah I see. So length doesn't make a difference (as long as it's long enough) in terms of how much energy you collect, but thickness does? That's weird. I like your tree analogy, that makes sense. Thanks for clearing that up.

Also thanks for your input N8, good to see you are learning even though your motor wasn't running at the time

I guess that explains the negative effect I noticed when I put the 2 power windings of my tri-filar coil in series. Putting them in parallel to use on 1 transistor as 1 wire popped the transistor when it wasn't connected to a charging battery, although in that instance it wasn't earthed, and was attached to a battery on the input as opposed to a PSU so no current limit, so I can't actually be sure as to what popped the transistor in that case. I'm assuming it was due to using both wires in parallel as 1 wire.

**blackchisel97** · 04-19-2011, 12:52 AM

Originally posted by dR-Green View Post

Ah I see. So length doesn't make a difference (as long as it's long enough) in terms of how much energy you collect, but thickness does? That's weird. I like your tree analogy, that makes sense. Thanks for clearing that up.

Also thanks for your input N8, good to see you are learning even though your motor wasn't running at the time

I guess that explains the negative effect I noticed when I put the 2 power windings of my tri-filar coil in series. Putting them in parallel to use on 1 transistor as 1 wire popped the transistor when it wasn't connected to a charging battery, although in that instance it wasn't earthed, and was attached to a battery on the input as opposed to a PSU so no current limit, so I can't actually be sure as to what popped the transistor in that case. I'm assuming it was due to using both wires in parallel as 1 wire.

Well, the length makes a difference since there is a higher inductance but there is no need to wind more if you can get the job done with less. Too much wire may cause your coil to self oscillate. It will become a solid state but spikes won't be powerful enough to charge. What you may get is referred as "surface charge".

You have to make sure your charging battery is connected before you connect your input. Even with wheel not spinning. If your circuit decides to start oscillating it will switch the coil on and off very fast. The moment when goes off, coil field collapses and Bloch Wall opens wider. (This is analogy to the magnet; energized coil has two poles and zero/nul/neutral zone in the center). Same as magnet. This narrow area called a Bloch Wall will expand when coil re bounces due to the collapse of magnetic field. During this moment more energy can flow in from the vacuum (or Zero Point). The effect is manifested as high voltage, sharp spike which can kill transistor before that poor thing will realize what happened.

If I may suggest something

- leave third winding alone for the moment (if it has correct length). There is something interesting to be done with it - if you wish. Get bifilar part going and tuned first and see what it can do.

Vtech

**ren** · 04-19-2011, 01:09 AM

Originally posted by dR-Green View Post

Ah I see. So length doesn't make a difference (as long as it's long enough) in terms of how much energy you collect, but thickness does? That's weird. I like your tree analogy, that makes sense. Thanks for clearing that up.

The thickness of the wire will determine its resistance for a set length. Resistance determines the amount of current the wire can support. A low resistance is exactly that, it offers low resistance to the passage of current.

One of the reasons multiple strands are used in parallel is to lower the resistance/impedance of the coil.

As has been stated above, there still needs to be a minimum level of inductance when using these coils in a motor/monopole configuration. In solidstate there are ways to force the transistor to self oscillate (without the need for a passing magnet to trigger it) which opens up the door to different coil designs. Ive wound short single layer coils in the bifilar configuration which have much lower inductance compared to the solenoid design.

What you must understand is inductance plays a vital role in choking current as well. The larger the inductance, the longer it takes for the magnetic field to establish itself generally. Once the magnetic field is established it is no longer dynamic and thus current is no longer changing and is being dissipated as heat, not what we want, unless you plan on heating something with your electromagnet.

I dont see why the coil cant be any desired resistance, what is important to note is how this one variable can effect the system as a whole. A higher resistance coil may just need other variables like input voltage to be altered to compensate.

Regards

**dR-Green** · 04-19-2011, 01:12 AM

It's already working, I was just playing around with different configurations

I've been trying things where leaving the 3rd winding alone gets in the way as far as I can make out and it affects what I'm trying to do, so I was trying to remove that problem by making it up to be 1 (thicker) wire, also to find out what effect that had. I don't usually have a problem with not having anything connected to the output, I've been trying to do it lately (using one transistor as you suggest in case of damages) while watching the scope to get an idea of what's going on when there's no charging battery connected. 220-300v spikes

I don't get this tuning business though. On the whole I haven't had any multiple triggerings etc getting in the way (I now have 2 machines, a bi-filar and a tri-filar), at first I thought I was missing something because there was apparently no need to tune it, but it seems that under normal operation, on these two particular machines so far at least, it's just a matter of how much current do I want to be using and how long do I want to wait to charge a battery. If it's connected to a PSU on the input then I just leave it on 680 ohms and be done with it. Unless I'm still missing something

**dR-Green** · 04-19-2011, 01:38 AM

Originally posted by ren View Post

The thickness of the wire will determine its resistance for a set length. Resistance determines the amount of current the wire can support. A low resistance is exactly that, it offers low resistance to the passage of current.

One of the reasons multiple strands are used in parallel is to lower the resistance/impedance of the coil.

Well, now I think I'm starting to understand. But then, couldn't you adjust the ratio of length to thickness, and increase one as you decrease the other to keep the same resistance over the whole wire? The reason I'm thinking along these lines is to do with tuning the coil itself to whatever source we are trying to tap, like in some Tesla devices. Or is this completely irrelevant on an SG?

[edit] Oh yeah, when you say multiple strands in parallel, do you mean connected to multiple circuits (transistor per wire), or multiple wires connected to the same transistor?

**blackchisel97** · 04-19-2011, 01:42 AM

Originally posted by dR-Green View Post

It's already working, I was just playing around with different configurations

I've been trying things where leaving the 3rd winding alone gets in the way as far as I can make out and it affects what I'm trying to do, so I was trying to remove that problem by making it up to be 1 (thicker) wire, also to find out what effect that had. I don't usually have a problem with not having anything connected to the output, I've been trying to do it lately (using one transistor as you suggest in case of damages) while watching the scope to get an idea of what's going on when there's no charging battery connected. 220-300v spikes

I don't get this tuning business though. On the whole I haven't had any multiple triggerings etc getting in the way (I now have 2 machines, a bi-filar and a tri-filar), at first I thought I was missing something because there was apparently no need to tune it, but it seems that under normal operation, on these two particular machines so far at least, it's just a matter of how much current do I want to be using and how long do I want to wait to charge a battery. If it's connected to a PSU on the input then I just leave it on 680 ohms and be done with it. Unless I'm still missing something

680 Ohm as you have might happened to be the right value. What tuning means is that you want your circuit to run efficient. Too high resistance may result in self oscillation or poor charging. Your spikes won't be as high as they could. Too low resistance will cause more current flowing through the coil and transistor and result in heat - which is a waste. The beauty of these circuits is that they can run cold and efficient at the same time. They are energizers, not motors. You don't aim at highest speed because best charging doesn't happen there. It happens at lower speed, just before your wheel or rotor suddenly starts to spin fast.
When I was talking about a length of a wire I was just being practical. Of course you can wind much more and still get it to work by changing other details - as ren said.
I have 1400 turns coil and working fine. The reason was that I salvaged some wire and didn't want to cut it so I wound on the spool.
The best way to tune it is with a scope but also can be done with LED strobe or by 1 Ohm test (measuring potential across 1 Ohm resistor in place of charging battery).

Multiple parallel windings - multiple wires wound together but connected to their own transistors - If I follow ren's line of thinking.

Vtech

**dR-Green** · 04-19-2011, 02:06 AM

Originally posted by blackchisel97 View Post

680 Ohm as you have might happened to be the right value.
The best way to tune it is with a scope

To be more precise, I have a 680 ohm resistor with 1k pot, and I can't make it go crazy on the scope at any point on the pot unless I'm changing the resistance too fast or whatever and the rotor is tripping over itself. So that's what I mean by I don't see any need to tune it, with respect to multiple triggerings. 680 ohms just happens to be the lowest it will go without changing the resistor

So to put it simply, I guess it's just a matter of what do I think is a reasonable amount of current to be using and temperature of the components? I haven't really been going for higher RPMs (apart from experimenting with higher frequencies as solid state) because the only thing I've really used my tri-filar machine for since I built it is to restore a dead 36Ah car battery, which damn near took 6 weeks with all the experimenting with different circuit configurations and what not lol. So that's another reason I have decided to leave it on 680 ohms otherwise I'll be waiting all year

**Neight** · 04-19-2011, 02:40 AM

apparently my coil was not causing too much resistance to make my motor work, as I have not changed my coil yet, and it is working. Though i do feel like i could get even better performance out of reducing the coil length and resistance, so I will be working on that in the next few days.
Trying to optimise my system for power draw and output!
Trying to help in what limited way i can atm!
regards,
N8

**blackchisel97** · 04-19-2011, 02:48 AM

Originally posted by dR-Green View Post

To be more precise, I have a 680 ohm resistor with 1k pot, and I can't make it go crazy on the scope at any point on the pot unless I'm changing the resistance too fast or whatever and the rotor is tripping over itself. So that's what I mean by I don't see any need to tune it, with respect to multiple triggerings. 680 ohms just happens to be the lowest it will go without changing the resistor

So to put it simply, I guess it's just a matter of what do I think is a reasonable amount of current to be using and temperature of the components? I haven't really been going for higher RPMs (apart from experimenting with higher frequencies as solid state) because the only thing I've really used my tri-filar machine for since I built it is to restore a dead 36Ah car battery, which damn near took 6 weeks with all the experimenting with different circuit configurations and what not lol. So that's another reason I have decided to leave it on 680 ohms otherwise I'll be waiting all year

Where did you connect your scope probe?

Vtech

**dR-Green** · 04-20-2011, 03:29 PM

Originally posted by blackchisel97 View Post

Where did you connect your scope probe?

Vtech

Probe A on transistor collector, and then sometimes I have Probe B on the base to see what's going on there. (But I can't enable "Glitch Detect" to see the HV spikes which it considers to be "noise" when I'm using A + B so B is off most of the time.)

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How big is too big? (Bedini monopole coils)

How big is too big? (Bedini monopole coils)

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