This is it !

[gmeast]

interesting scope captures

Hi all,

I want to share a couple of scope captures of an air-coil that weighs about 5Lbs.

The following pics are of the same setup, just at different time scales. Also res_air0 is is the classic 'ringing' everyone has seen. The scales are on the pictures. The Green trace is battery(-) or ground.
http://02d1852.netsolhost.com/radian...g/res_air0.JPG

res_air2 is the same as res_air0 but with the frequency raised so that ALL of the ringing oscillations are gobbled up except the first negative-going spike.
http://02d1852.netsolhost.com/radian...g/res_air2.JPG

res_air1 is res_air2 at a different time scale.
Please notice that most of the spikes (or at least the spike 'volume') are negative-going. Notice the big negative bump on the (-) part of the waveform opposite the biggest (-) oscillation on battery(-). THAT is a 'Pulse Charge' ... albeit on the battery's cute little behind: where most folks are not accustomed to seeing a charge placed.
http://02d1852.netsolhost.com/radian...g/res_air1.JPG

This 'holds its own' on the battery. It does NOT discharge the battery. It appears to have the possibility of being a self-charging configuration.

**************THERE IS NO DIODE IN THIS SETUP************

What's hard to realize is that the actual 'fall time' is as fast as the 'rise time' ... which is a few hundred nanoseconds as far as what the switch (transistor) is doing. The 'fall time' shown in the scope capture is actually the first 'negative-going' oscillation. But you can't see the 'fall-time' characteristic of the switch because the pulses are scrunched up together to create the waveform you see.

As I write this, the temperature is dropping yet the voltage in the battery is creeping up ever so slowly.

******I MUST STRESS THAT MY TRANSISTOR IS STAYING STONE COLD******

Well, I'm excited. Enjoy

Greg

[Farmhand]

Hi greg, those are interesting shots. You should be excited looks like your making good progress.

When you get time to make a cicuit drawing i'll have a go at that. I got some new equipment and some parts, I wasn't sure what componants you are actually using now, I thought I would wait until you'd made a decision on which parts you will end up using.

I've got mountains of work to do and the rain has stopped, now it's darn hot and humid like a sauna. No AC here for me.

I wondered if it was possible to charge a battery by making the - go below zero rather making than the + go higher. Is that what you have happening ?

I still need to get wax and wire and winding tape.

It seems to me that four primaries like in the Tesla drawing would work much the same as three, Bob probably used three for some reason though, I wonder why.

Actually with a choke on the charging line would a diode be necessary, wouldn't the choke stop the back flow but also allow negative oscillations through ? I have no idea. I think the diode would stop any negative element from passing wouldn't it ?

Boy oh boy this is more complicated than I first imagined.

Anyway I have to do some outside work in the sun, so I may be too messy to use the computer for a couple of hours. I have muck raking to do.

Back later, i'll think while I work.

[cikljamas]

Maybe this can help somehow someone :
watkykjy1 - nilrehob

[gmeast]

might can help

Maybe this can help somehow someone :
watkykjy1 - nilrehob

Hey cikljamas,

Thanks allot! This is what I pictured it as. I also see that the freewheeling diode is shown for the IRF540Z. It has an internal but I think the sketch means that. I have to look up the MUR410 charge-circuit Diode ... wonder if it's special.

Thanks cikljamas. Later

[cikljamas]

Hey cikljamas,

Thanks allot! This is what I pictured it as. I also see that the freewheeling diode is shown for the IRF540Z. It has an internal but I think the sketch means that. I have to look up the MUR410 charge-circuit Diode ... wonder if it's special.

Thanks cikljamas. Later

I am glad if i can help at least by patrolling other threads...
So, you are not alone, not at all, we are here stuck as label to the box...

Cheers !

I hope your diagram is on the way

[Farmhand]

MUR410 is an ultra fast rectifier, 25,50 ns

MUR410 pdf, MUR410 description, MUR410 datasheets, MUR410 view ::: ALLDATASHEET :::

Nice diode.

I have some 1n5822's they should do.

1N5822 pdf, 1N5822 description, 1N5822 datasheets, 1N5822 view ::: ALLDATASHEET :::

Maybe

[gmeast]

Mur410

MUR410 is an ultra fast rectifier, 25,50 ns

MUR410 pdf, MUR410 description, MUR410 datasheets, MUR410 view ::: ALLDATASHEET :::

Nice diode.

I have some 1n5822's they should do.

1N5822 pdf, 1N5822 description, 1N5822 datasheets, 1N5822 view ::: ALLDATASHEET :::

Maybe

Thanks Farmhand

[7imix]

Hey guys. I got a very fast op amp and built the op amp impulser with some high precision pots to allow for very fine tuning. I am very very pleased with the circuit. It works extremely well. I have been busy and haven't made a full video but very soon I will be testing some of my faster mosfets with it and will make a video.

cikljamas, I think I made some mistakes with some of the component values in the unijunction transistor circuit. I don't think it's going to be easy to find a unijunction transistor that has fast enough rise times though, so the op amp circuit is probably the way to go. Also if you don't have an oscilloscope you are going to have an impossible time with this project -- you need to pay very close attention to the shape of the waveform and the frequency of the oscillation. Try to find an old scope or pick up one of the little dso nanos, otherwise you will just be banging your head against the wall in frustration.

The op amp chip that I am using now is the NTE859. It has a slew rate of 13v/us.

[gmeast]

tle2074

Hey guys. I got a very fast op amp and built the op amp impulser with some high precision pots to allow for very fine tuning. I am very very pleased with the circuit. It works extremely well. I have been busy and haven't made a full video but very soon I will be testing some of my faster mosfets with it and will make a video.

cikljamas, I think I made some mistakes with some of the component values in the unijunction transistor circuit. I don't think it's going to be easy to find a unijunction transistor that has fast enough rise times though, so the op amp circuit is probably the way to go. Also if you don't have an oscilloscope you are going to have an impossible time with this project -- you need to pay very close attention to the shape of the waveform and the frequency of the oscillation. Try to find an old scope or pick up one of the little dso nanos, otherwise you will just be banging your head against the wall in frustration.

The op amp chip that I am using now is the NTE859. It has a slew rate of 13v/us.

Hi 7imix,

Glad you found a good one. I'm using the tle2074. It boasts a slew rate of 45v/usec. I used the leftover amp as a summing amplifier to provide an offset adjustment and I'm glad I did because I've been using it to drive a 2N2955 transistor. I'm getting 400nsec rise time pulsing a transformer primary at 34kHz and almost rail to rail battery (avg 12.75VDC) and the transistor stays stone cold ... or nearly so.

We might be successful using this approach.

Later

[Farmhand]

Ok i'll ask the nooby question.

So 45v/usec is better than 13v/usec ?

Anything else special I need to go with that ?

Ta.

[gmeast]

v/usec

Ok i'll ask the nooby question.

So 45v/usec is better than 13v/usec ?

Anything else special I need to go with that ?

Ta.

There are other limiting things such as a coil's capacitance as well as its inductance and reactance to slow things down. Mosfet drivers are a niche thing. It seems like you need the right one (and kind) for the job. The Hex Controller uses gate drivers. I've been pouring over these things and the manufacturers of these driver ICs are quite specific as to what driver waveform should be used for what kind of load ... resistive or inductive or some of both ... I think there is always some of one in the other. I know I can ping a carbon film resistor and get oscillations.

You already have logic-level device experience. There are volumes of books written on 'Designing for Mosfets' ... where to start? I know I'm no expert on the things myself. I would think you would put some sort of bias, maybe drive it with a signal diode or opto-isolator ... I believe some drivers integrate opto-isolation into their architecture ... not sure ... think I read it somewhere.

Later

[Farmhand]

Ok i'm going to go ahead and make two fairly quick gate drivers and try to work out how to lock them 180 degrees out of phase to each other.

Still no core's and it's friday afternoon, the 17th, hope they come next week, not really a good time of the year to get stuff mailed. Oh well.

I've slipped a disc in my back now, in the vertebra right at the base of my rib cage. I'm in agony and doctor don't believe me.

So when I get my toroid core wound and a working circuit, i'm gunna swirl the hell out of it. I don't have a lot to lose. With any luck i'll get hit by lightning, survive and get some proper medical treatment for my spine.


Cheers all

[gmeast]

struck by lightening

Ok i'm going to go ahead and make two fairly quick gate drivers and try to work out how to lock them 180 degrees out of phase to each other.

Still no core's and it's friday afternoon, the 17th, hope they come next week, not really a good time of the year to get stuff mailed. Oh well.

I've slipped a disc in my back now, in the vertebra right at the base of my rib cage. I'm in agony and doctor don't believe me.

So when I get my toroid core wound and a working circuit, i'm gunna swirl the hell out of it. I don't have a lot to lose. With any luck i'll get hit by lightning, survive and get some proper medical treatment for my spine.


Cheers all

There we go ... my way of thinkin' ... the indirect approach. Somehow it all makes sense.

[Farmhand]

Any idea's for a phase lock ? I suppose I would need some flip flop thingy or some 555's or something like that.

Also slightly off topic, I have some copper coated carbon rods 10mm diameter 300 mm long, can carbon be used for a coil core? Because its conductive. I wonder is it magnetic ?

I also have some flat one's 15 mm x 5 mm x 300 mm Maybe I can use one of those to make a big sliding potentiometer ?

That could be usefull.

Cheers all

[Farmhand]

I thought it might be worth a mention that in Tesla's time I don't think they had a way of actually measuring frequency. I think that is why we see in documents the phrases "reletively high", "high", and "very high frequency".

Now unless a spark gap was used they would have been restricted in operating frequency relative to the number armatures or commutators or whatever and the speed they could rotate them at, (excluding resonant causes).

So it stands to reason to me that the phrase "high freqency" would probably refer to the Khz range, probably only the lower part of it and the phrase "very high frequency" would have been anything over that.

So i'm thinking for the effects we want, really high frequencies will not be necessary, just better. A bit of accuracy and phase adjustment should be all that is needed.

Of course the sharp rise and fall times are important, in my opinion.

Well thats how I see it, we really do need to swirl it and put some extra wire in there that we are not directly pulsing (secondary).

There is obviously no harm in having a secondary in there. Going by the vids.

The secondary might be the origin of another different frequency.

Cheers all.

P.S. I've just discovered IC sockets are very usefull. and cheap.