Mosfet Heating Circuits

[Harvey]

Hi Gad,

Can you give us a snapshot of how your probes are connected to the circuit?

I notice that in one of the shots we are getting good clamping by the internal diode but in the other there is some shoot through and that is the one that looks as if the CSR has a superimposed frequency on it. Also I notice (but very hard to read because of the blurring) that you have Volt Avg set on one screen and on the other you are setting the trigger? Hard to tell for sure what is happening. But perhaps something is setting the DC or AC coupling in different settings? I'm also not sure of what you mean by "Battery or load Resistor". Do you mean that one of the shots was across the battery and the other was across the load resistor?

On the 555, the one pot is supposed to adjust the amount of time the gate is high and the other pot adjusts how long the gate is low. So they both impact the frequency and duty cycle but because the base settings were originally structured for "3.7% On" the effects are greatly imbalanced. Reducing the capacitance on pin 2 will increase the frequency while increasing the overall pot resistance path will lower the frequency. The series resistors in line with the pot set the base settings and then the pots deviate from there. I can help you tailor it to your specific needs if you tell me what they are.

[gadh]

Hi Gad,

Can you give us a snapshot of how your probes are connected to the circuit?

See attached (ignore the 555 circuit part - mine is newer, according to your modifications)

Do you mean that one of the shots was across the battery and the other was across the load resistor?

Yes, as i mark in the images filenames.

[Guruji]

Hi Guruji,

That's what Glen's circuit seemed to do and that's why everyone got excited because it got hotter than expected and ran longer than expected based on the preliminary expectations. It was not until I did the transient analysis here in this thread that I fully grasped how the energy was being moved around and misread. But even then, there does seem to be some extra energy but the tests are inconclusive to pin down the exact detail

Thanks Harvey for response. Is it possible to post Glen's schematic?
Regarding the inverter I thought to put it on the resistor only not the whole circuit.
Thanks

[Harvey]

Hi Gad,

Now I see the file names

All three grounds (blue, red, purple) need to be the exact same physical position. Otherwise any voltage produced across the inductance of the wire between them will cause a current to flow in the probes reference leads and that can cause weird readings.

One thing I see in your pics is that the BEMF energy is passing right through the resistor as if the resistor has no impedance to it. In Glens pics, it can be seen that this energy is almost fully dissipated in the resistor and according to my analysis that is where the heat is coming from.

In other words, the battery shot should look almost flat except for an inductive bump from battery wire inductance and the energy should be greatly filtered by the battery capacity. You may want to review Glen's pics to see the difference between the Battery and the Load shots.

If the energy is passing right through your resistor, then we have to ask why. Perhaps it is passing 'around' it via some type of capacitive relationship due to the Teflon between the windings. The dielectric of the Teflon may be storing the energy and passing it from winding to winding instead of forcing it to go around the loop of each winding essentially bypassing the resistor. I wonder if it would read on a capacitance meter

I hope that helps. Please keep in mind that you are working in uncharted territory as your resistor is unique. But you are certainly asking the right questions

Does your battery get warm during the tests?

[gadh]

No, my battery does not get warm at all.

[Mr.Whip]

Interesting resister change

Hello all Just wanted to post a note that I'm getting very exciting results using a Toroidal Mobius coil for my resister. Easy to make and try your self.
Mobius Coil winding tutorial - toroidal . The only thing I did different with my coil was make mine bifillar and connected the end of one wrap to the begining of the second. I used 2= 120' lenths of plactic coverd solid copper door bell wire. Looks to be like 14 gauge. Much more heat than my same ohm resister. Or I just might be over reacting.
Great thread, informative posts Thanks
Randy

(Sorry not 14 gauge it was 18)

[gadh]

Hi Mr. Whip.
could you please explain what are the exciting results you've had ?

[Harvey]

No, my battery does not get warm at all.

Interesting

It makes me wonder where the energy is going that is represented in that high voltage across the battery. Is it bouncing back through the resistor a couple of times and being dissipated, or is it being passed capacitively through the battery and dissipating in in the MOSFET body diode?

I suppose it could be radiating some.

When Glen had the best results, the ringing was practically non existent and all of the energy was spent on the resistor. In that case, the voltage bump on the battery was less than 1/10 the BEMF on the Drain. I even talked with him about the battery bump being an illusion due to the inductance and length of the wires leading up to the scope measurement location that was some feet away from the battery. Also, when he placed a meter directly on the battery we did not see that bump in the average voltage so I questioned that it was really there.

Your shots seem to show nearly all of the BEMF on the battery side of the resistor as well as on the Drain side and that's curious.

[Harvey]

Hi Mr. Whip (Randy),




So are you getting heat from your plastic coated wires? If so how much?



EDIT:
240' of 18 AWG at .00639 Ohms per foot is 1.5 Ohms - does that match your winding resistance?

[Mr.Whip]

Mobius coil

Hello everyone: Actually Harvey I was just guessing on the wire lenth. But the coil had 3--3.2 ohm. I'll have too post more once I return to my shop. I'm in China right now and cannot access Youtube from here. China locks us away from many sights here. But I'll post more when I return too USA. The mobius toroid gave off much more heat than a wire wound resister (Self wound) of 3 ohm. I'm just wondering if it was because of the magnetic streams on the outside of the wires crossing because of the mobius wind creating more heat. I have no measurement equipment here. For me this will have to wait. But for those who are trying different resisters You could wind a mobuis with 10 ohms or what ever Ohms you would like. and try it your selves. I just happen to hook up and mobius coil I had wound for another project.( Watch out for the coil levetating off the table at higher freq. JUST KIDDING)

Randy

Opps I forgot to meantion that I used 2 wires like 120' + each in the wind so like around 240 + feet Aprx.

[sucahyo]

Hello all Just wanted to post a note that I'm getting very exciting results using a Toroidal Mobius coil for my resister. Easy to make and try your self.

I thought that iron heat up because of changing magnetic flux? Wouldn't zero flux of mobius coil make the iron cooler?

[Harvey]

I thought that iron heat up because of changing magnetic flux? Wouldn't zero flux of mobius coil make the iron cooler?

Why would that have zero flux?

[Harvey]

Hello everyone: Actually Harvey I was just guessing on the wire lenth. But the coil had 3--3.2 ohm. I'll have too post more once I return to my shop. I'm in China right now and cannot access Youtube from here. China locks us away from many sights here. But I'll post more when I return too USA. The mobius toroid gave off much more heat than a wire wound resister (Self wound) of 3 ohm. I'm just wondering if it was because of the magnetic streams on the outside of the wires crossing because of the mobius wind creating more heat. I have no measurement equipment here. For me this will have to wait. But for those who are trying different resisters You could wind a mobuis with 10 ohms or what ever Ohms you would like. and try it your selves. I just happen to hook up and mobius coil I had wound for another project.( Watch out for the coil levetating off the table at higher freq. JUST KIDDING)

Randy

Opps I forgot to meantion that I used 2 wires like 120' + each in the wind so like around 240 + feet Aprx.

You mean like this one?: YouTube - Antigravity Technology Boyd Bushman Lenz Levitation Law

[sucahyo]

Why would that have zero flux?

Maybe wrong term. zero induction?

[gadh]

to Harvey

Hello Harvey.
i finally got my hands on a professional RCL meter , and measured my load resistor's RCL values. The device allows measuring at max. 100khz so that's what i've used:
R = 11.2 Ohms (I assuse its resistance, not impedance)
L = 23.36 uH
(at 1khz, L = 23.5 uH so we can assume that in 200-300khz the L would not change much as well)

parasitic capacitance between windings:
1 binding = 0.93pF
between 2 bindings = 0.83pF
between 3 bindings = 0.80pF

My question:
Since the load resistor in the first reported test was measured as 8.64uH, and mine is 3x greater , should i change the 555 frequency range acordingly (in order to seek properly for the right resonance freq.) ?
which values should i change in the 555 circuit ?

Thanks in advance,
Gad