Nathan Stubblefield Earth battery/Self Generating Induction Coil Replications

[MW383]

Regarding induction heating....

I have 1st hand knowledge of these and do play with commercial units of this nature. Basically they take an alternating current and throw into a pancake coil. The circuitry is complex but along fundamental lines that Tishatang discusses. These are high frequency devices 25-50Khz. Assuming proper cookware placed on them (something ferrous), the circuit senses current draw on particular piece of cookware and applies current to the coil accordingly. Circuit is tuned from impedance aspect to recognize ferrous cookwares. I have heard that they can be tuned for other materials such as aluminum but this is not done in the industry as of yet.

I have buried a pancake coil and ran at a 400w power level. Frequency decreases as power increases with these things. It is my craziest experiment so far. The problem here is that I believe 25K frequency way too high. The other problem I have is in tricking the circuit into thinking it has a piece of cookware on it because if it doesn't sense cookware, it will not operate. I got around this eventually. I have noted that as long as I have a field running, it decreases in frequency the further you move away from coil. So indeed I can have frequencies below 10Hz at certain distances away from the coil. This is still not an ideal experiement though but I will post any interesting findings I may come up with.

As you move up the frequency scale you get to devices like microwaves. I worked on designing a combination microwave / convection oven once. It was a nasty combination because you cooked food placed in it internally via the microwaves and used the convected heat for browning purposes. We used to take frozen pizzas and cook them perfectly inside and out in 2.5 minutes. And that was from a cold start of the cooking unit. Thinking back though, I hate microwaves because no matter how much faraday type caging is done, I can physically feel them whenever I am near them. This is the same reason I hate commercial induction cookers, I feel them too.

[jeanna]

MW383,
I know what you mean about feeling these things.

Now, are they not using a standard wall outlet and transforming it to higher voltage?
If so, that means to me that the wave is still a sine wave, and the rate of change is slow. (which means shape not really speed.)

A straight up then straight down spike is what we want.
You won't feel a bad feeling from that either!

So, can this kind of thing make a ferrous coil get hot enough to cook?
Or, I don't care aluminum would be ok too, cuz you can use tankless hot water heat transfer once you get the heat.

I have wanted to try this for a while, you can tell.
Do you still have this set up? If you do, I guess you haven't made a joule thief yet... darn! always something! 

thanks,

jeanna

[MW383]

Now, are they not using a standard wall outlet and transforming it to higher voltage?

I will get back to you on exact circuit function. I am under the impression that the main portion of the circuit is supplied by 18VDC after conversion from higher AC input. I also know that there is ultimately an alternating current going into the core. What happens in between I will have to check.

A straight up then straight down spike is what we want.

Circuit above does have a resonance circuit within it but I have to get the details. From what I know it switches at a zero point (not sure if voltage or current being = to 0) Rumor has it we are getting an oscilliscope. When we do you can be sure I will be checking out waveforms.

So, can this kind of thing make a ferrous coil get hot enough to cook?

For general cooking in the kitchen it works fairly well. It is 90% efficient which is above standard resistive heating systems and also above gas based systems. Through controls, you have essentially 100 unique power increments so if making candy, an omelette or something tricky like this, then induction would give precise control of the process. Inexpensive consumer units can be had for less than $100 (single hobb). These are generally of very poor quality and have a high failure rate. The ones we make at work are for commercial cooking industry and are way more rugged.

For screwing around, the pancake coil can be dumped and replaced by tubular coil (like we are familiar with). In this case an induction cooker drawing only 100watts @ 120VAC, will take a piece of ferrous metal up to 800F. Run 1000watts and the metal will glow bright red. One must be careful when swapping coils like this because the induction circuits very complex. One needs to stay within a few general parameters otherwise you will most likely ruin the unit. There are a few youtube videos where people have hacked them to these effects. I reproduced their results quite easily. Heating the end of a screwdriver to cherry red not my bag but this method of heating metal very popular in industry for quite some time now. I have something much cooler in plan...

Coil still in the ground. Basically I sealed it within a vacuum seal bag. I didn't really have to do this because all copper windings are coated. I did it because once I am done in the dirt I want to reconfigure it into the cooler thing I mentioned. So basically I didn't want dirty. I can get all kinds of strange things to happen in ground and around simple EB's. It's so inconsistent and finicky though that I have little sound results on anything yet. Basically an induction cooking system very unoptimal for ground work. We need ULF interaction not this high stuff.

Main problem with my test unit is the circuit is not easily hackable. Way too complex and way too many inter-relating things going on, not to mention a ton of logic held in a CPU. I have hounded our induction engineer about many of its aspects, like dumping current sensing option, its ferrous detection scheme, lowering its frequency, having manual adjustability to frequency, etc.... Basically you can't do it easily because every aspect of it is optimized for cooking. I also asked about just isolating/modifying the switching circuit in order to pirate it into our sort of uses but got the same reply 'not easily done' Oh well....

Meanwhile, I think Tishatang has made some very interesting posts of late....

[Pirate88179]

For what it is worth, I too can "feel" when the microwave is on.  I can also "feel" when I put my cell phone in my hip pocket, which I hardly ever do now.

These are great posts you guys (and Jeanna) and I hope to be able to contribute more soon.

Bill

[jeanna]

@MW383,

The problem here is that I believe 25K frequency way too high.

I would agree if you want to keep using high amps draw.
What I am working on in my mind is that since the frequency goes down when the voltage goes up, it might be doing something similar to amps when in a pulsed circuit.
Frequency is not really a thing, but if you look at it as the number of times the voltage passes by an 'amp' spot then many of them and fast, might do the same work.
(I also think the 'amp spot' is the moment of change from one direction to the other which as we know creates very high volts- -- Now,because at that moment the resistance is also low , then, I=E/very small number which also means I is also very high at that short moment)
So, I want to avoid the lower frequency to start it. (25k is possibly high enough.) I have also seen that the frequency will drop as the draw pulls power from the pulses.
So, I am trying to steer you  into trying this too. (rude of me but if you know about it then maybe it is not so rude.)

Thanks for all this information.
Do you have a suggestion about a ferrous material?
Should I use one of these welding rods I got for the bedini? (soft iron)
or...
My hardware store has this really thick copper wire. 1/8 and 1/4" diameter. expensive, but an immersion coil only would take a little, Do you think this is the right direction? or do you think iron is?
I know there is only one way to know... I'm just asking while I am wondering.

thanks for your valuable input.

jeanna