This picture is amazing once you figure out what happened. I will let you guys ponder a bit at today's interesting scope shot.

EDIT: Hint, the "T" in the top left of the picture is the scope trigger point, 0 rpm to the left. After many many attempts for personal rpm record and I did get my high record of 3.34 Mrpm on Friday (5-17-2019), I always set the vertical cursors to my current record (in microseconds), so I can see when I beat my personal best.

I usually prepare 10~15 balls for testing that day, one day, I got to this one ball, I guess things were just right (ball/container/angle/settings). What happened was amazing and unbelievable, with about ~250W (18V ~13A). First hall sensor trigger, it gave a ~0.25 second burst, I could hear the power supply give a quick 60Hz hum, sucking some juice, then the scope displayed high 2 million rpms! WTF! The major keys it was legit was no vibrations and the ball was still spinning down from momentum. I have been running the scope at 10us/div (since going for 2+ mil), but I decided to get the big picture, zoomed out the scope to 100ms/div and set single trigger and tried again, moved the hall sensor into position and it happened again, a burst of around 200~250ms then hall stops triggering the coil. I zoom the scope into the end of the coil drive signal, this time just over 3 million in a quarter second! I stopped to think about it, no Ford transmission vib's, just pure signing spinning ball. Blown away I called a friend to witness what happened, I did it 4 more times, the most impressive time was in the picture, it shows 0 rpm to 3.2 million rpm in ~25ms!. That is an average 130Krpm acceleration every 1ms. This is what happens when you pump in~ 250W (1/3HP) to spin a 3mm ball that weighs nothing (~0.11g) AND everything is close to optimal. I have seen something similar before during testing, just not starting at 0 rpm, it hit 3.5 mil and 4.1 mil once, but I did not believe it, I did not know what was going on then, so I never posted it.

From my 40+ years playing with motors and racing, I knew the first time I saw 300K rpm on YT that containing the ball was a key instead of letting it thrashing around, efficiently coupling the flux to the ball and timing. 5mm balls were relatively simple, switching to 3mm balls was much tougher to solve. My method works (nylon standoff drilled to let the ball drop in, then contain with with a nylon screw), but by far it is not optimum, I liked that it was low cost, I can prepare a bunch before testing and provides some safety, much more than the 5mm spontaneously disassembles with a punch. I have some more ideas, but each one is more $$ and more time to develop it. I like the technical challenge, thinking of ideas, building, testing, tuning, retesting, repeat.

Nope, ain't see nothing.

wow cool, cant wait for an update.

btw.  i use c3998 transistors, they designed for tv flybacks. - 1500v and up 20amps.  -   they might be abit oldschool.  - but pretty cool i think, - ive driven up too 400watts for 1min through them with resistive loads. -  - also use them for high current, low voltage in my psu's,  try 2 use them for everything so get too know them well, - and by far best so far in my newman motor,   - my front line bad boys,  noob friendly too.  , and usually about $1,10 usd each on ali express. -

https://youtu.be/ZQE05T-3680

Today: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's
And two more dead fets, I think its time to tackle this issue, 80V from the coil (60V from flyback, added to the 20V from the power supply) on a FET rated for 55V (min, they dont give a max spec, weird)

EDIT: I remember when I was trying for 1 mil, or 60us period, now if I am not hitting 20us I call it a dud. :fdrum: Now I am under 16us.
I just found a 700V fet, but its 9A cont and 27A pulsed, I dont think its going to last. :nuke:
EDIT: Nope, I didnt kill it, but that thing has 1Ω Rdson, so it gets hot doing nothing, lol. and it does not push the current I want. It came out of a cheap low wattage PC power supply. The semi high resistance is probably great for low emi.

Having trouble hitting 4 mil, blowing more fets, lucky they are cheap, actually these were free, robbed them out of a discarded UPS, mounted on the heat sink, 4 sets with 4 fets on each. But they are cheap, less than 50 cents each on ebay. I been lazy on adding a snubber, so that is next. I looked closer at the drain signal and it clearly shows why the fet is blowing, repetitive avalanche mode, this is the reason the drain voltage is clamped at ~65V (blue trave in 3.8mil picture above, I am clearly exceeding the fets max drain-source voltage. If the snubber does not work, I will be looking at better fets.To be clear, its not just the fets holding me back, I routinly get low 3 mil, but the balls give up 1 to 3 mil often, plus some other issues.

I still am not sure why the ball flashes when she gets upset :rant: But I got a good one today at a slow 1.5 mil, I video at 1080 and 60 frames per second, this was only in 1 frame.

How do you get the " Attachments and other options…" when you start a reply? I have to save the reply and then modify the reply for it to show up?

Quote from --Oz-- on May 24th, 2019, 06:26 PM

How do you get the " Attachments and other options…" when you start a reply? I have to save the reply and then modify the reply for it to show up?

Try pressing "Preview", that brings up "the rest" ;-)

wow amazing, 20us is fast !.  exactly as fast as i have ever managed too get down too.  -  really impressive,  16us is better !!. - really getting into the realm of professional hardware now.  ....  you may want too consider scrapping DC altogether and using a gradual ramping AC signal with RF transistors

Thanks. I am pretty sure the square wave applied to the coil is really a ramping triangle wave (coil current equals magnetic field strength). I am getting tired of blowing fets, going to try a RCD snubber, if that dont work, been looking at proper rated fets for this application, I am a team budget guy, I maybe have spent $20 on this project total. Its really amazing seeing the coil current increase by just increasing gate voltage (lowers RDSon dramatically). I mostly was running the hall sensor and fet driver at 5V, turning it up to 6 and upto 10 really ups the current. Playing with gate voltage and timing I got the coil current up to 93A (from 25 to 40A normally on 5V), see picture (1800W peak and 1000Wrms), I dont plan on running it that high normally. There is so many little things to fine tune/optimize. I did find something interesting on timing I want to test and understand better and then fine tune, also some different ideas on coils I want to build/test. I also want to try some different magnets, but I am having a hard time finding the dimensions and magnetic diametric orientation I want, Alibaba has them, but they want you to buy a pallet full of them, lol.

I remember finally getting to 1 mil (60us), improving to 50us was semi easy, now down to under 20, 1 or 2us is pretty tough. I have many ideas to try but requires time.

On the back burner, I have a idea, that might just work, but it requires a few relatively difficult things worked out to make it work, its pretty bold (read as "a lot of work" :) ) I wanted to crack 4 mil with my current setup and then start testing coils/magnets/timing, but currently with my setup, low 3 mil is pretty common (maybe 1 or 2 of of ten tries), but 3.5 mil and above not happening the last few days tring, I think I just got lucky with the 3.8 mil (the stars wear aligned).

Regarding microseconds, from:
16us to 15us is 250,000rpm increase, (4.0 mil)
15us to 14us is 285,000rpm increase,
14us to 13us is 330,000rpm increase,
13us to 12us is 385,000rpm increase. (5.0 mil)
12us to 11us is 454,000rpm increase.
11us to 10us is 546,000rpm increase.
10us to 9us is 666,000rpm increase.(6.0 mil)
9us to 8us is 834,000rpm increase. (6.8 mil)
8us to 7us is 1,070,000rpm increase.(8.5 mil)
7us to 6us is 1,430,000rpm increase. (10 mil)

Yeappers, its getting exponentially harder. Houston, I need more power!

wow nice work, - erm perhais i was wrong about my 20us. - now that i recall again, i think i was measuing fall times, - and got it down too ns's - 200/400 ns. - anyways that was a while ago, - working on rosemary Ainsley heater.  (which was fail).  but good fun too really attack.

i found the best way too acheive the times i was, - too supply significantly too much current too the base, - and pull it hard too ground with like 500ohm resistor ,  just slam the cunt shut and get out.

I am more of a FET guy, I would rather charge/discharge the gate cap than have a low gain bipolar transistor (they both have their advantages). I was looking at some fet drivers, last one I looked at was 12A, lol.

At work, we measure our data signal transitions in pico and now femtoseconds (not power stuff), with 4 lanes we getting 400+Gbps.

I tested a 600V 8A fet (MTW8N60E) today with no ball, input signal was function generator.
I made a simple 10:1 voltage divider so I dont kill my scope probe (blue trace, red is gate, green is coil current).
With 4V applied to the coil, I got a flyback of 670V and no fet avalanche seen on the scope.
5V and higher avalanche was 680V.
Also the higher voltage fet was only rated for 8A (24A peak), so this was really limiting the coil current and the flyback voltage. In this picture you can see the coil current tapering off as the fet could not handle the current.
Might try a TVS (Transient-voltage-suppression) diode, never used one before.
When I used a simple diode across the coil, it killed all flyback voltage great, but it limited my RPS to something under 10,000. I should look into why that happens, might try adding a resistor in series to see if that helps. 

Regarding fet avalanche, I found this application note that explains it well, check out the first figure if interested. https://www.infineon.com/dgdl/Infineon-ApplicationNote_Some_key_facts_about_avalanche-AN-v01_00-EN.pdf?fileId=5546d462584d1d4a0158ba0210977cde

In most of my pictures, you can see the avalanche clearly, poor low voltage fet taking a beating! lol
Since I avalanche even with 1V applied to the coil (flyback way over 65V), I think when I am pushing 10~15 amps rms and 2+ mil rpm, the repetitive avalanching heats the fet up alot, the heat and the voltage stress finally kill the fet.

I would be curious what the mega inductance newman motor flyback voltage is? Careful with your scope probe rating, make a voltage divider, maybe 100:1 or more.

Some new coils to try out, its easy to see where I am headed in the next experiment. Currently I am just using 1 pole and got to 3.8 mil. If the new coil setup works, I might try a full H-bridge, and maybe 4 poles down the road. Maybe monday I will test them.

UPDATE, the two coils on the right are complete failures, lol.

I got another idea while driving home, low inductance, high current. My current probe wont fit, maybe make a current transformer. Will try to test Monday.

Quote from --Oz-- on May 30th, 2019, 04:28 PM

In most of my pictures, you can see the avalanche clearly, poor low voltage fet taking a beating! lol
Since I avalanche even with 1V applied to the coil (flyback way over 65V), I think when I am pushing 10~15 amps rms and 2+ mil rpm, the repetitive avalanching heats the fet up alot, the heat and the voltage stress finally kill the fet.

I would be curious what the mega inductance newman motor flyback voltage is? Careful with your scope probe rating, make a voltage divider, maybe 100:1 or more.

Wowzer that is some serious stress on those transistors, - just how we like it, or not.... at long as im gentle with one of my trannies, i will ravage the others....  still feel like a nice guy.

hehe with the old newman though, - i did look at the spikes on the scope, - i recall it was pushing 300v, from 40v input, - but i suspect it may have been higher, and i just didnt have the resolution in my cheap 9yo digital scope, - 50mhz in digital is like 1mhz in analog because of the sampling rates, - dave jones did a video on it last week, - i always knew scope sampling rate was not good, but id never setup an experiment specifically too tested it, - and i was surprised too learn how woeful even the high spec new digital scopes are.

anyway speaking of this stuff,- i may a new photocoupler circuit for high speeds too use with my bucking coil transformer, - and newman too eventually.  -  the data sheet says the photocouplers are very slow, - 10us @ 10v 2kohm from ground, - and 3us @ 5v and 100ohm from ground....  which is obviously very slow, but too my supprise, i was able too pull it down a little further, and invert the signal a few times, and get it down too 20ns fall times....  so pretty sharp,   - i must admit i feel smarter than i did yesterday, staring blankly at my desk trying too solve this one  @ 2am. 

https://www.youtube.com/watch?v=pds1x_0XXT0

You know what might be really cool...?

Build yourself a setup using a high pressure air blast to launch one of these spheres, then chamber it in such a way as to get it spinning 2M RPM just prior to launching it.  I'd love to see what kind of curve ball trajectory this thing travels in.  You may surpass the well-known boomerang.  Or, with a different angle, it might make one heck of a crazy helix.

bro, or should i say, bra.

@ Patrick, i would of thought the mega inductance on the newman would of had a hell of a kickback (flyback).

I am guessing amps and inductance are equal in some way. Example, 10A 10uH will give say 100V CEMF (just a guess), If you lower inductance by 10 and raise amps x10 (100A 1uH) you will get similar CEMF. So even though your in the mA current range, I would guess with your several heneries of inductance, you would get some serious CEMF. Would love to see the voltage waveform across the coil. Ideally you would want a differential probe, but be careful what ever you try with too much voltage smoking your scope probe or your scope.

@Matt, haha, that you be awesome to try!

UPDATE: Low inductance, high current, i built part of it, the fets/caps/coil (1 turn). Its good to 1,000 amps pulsed if fets are kept cool. I am replacing my 16 turn coil with 1 turn (more like a single "U" turn). The only reason its as long as it currently is, so the current probe will fit. My current probe only goes to 50 Amps rms, so i plan on adding a secondary loop and scale it 20x. or maybe I will try a hall effect and calibrate it. Also need to add a 10:1 voltage divider on the drain. Quick testing showed 1V on cap gave 10A, 2V gave 20A and so on, this was with a quick mock up circuit with single fet and small 470uF cap. Drain flyback ring was 50ns period (20Mhz).

FYI, here is a nice inductance calculator https://www.eeweb.com/tools/coil-inductance

QUESTION: why is this website "Not Secure"? Most of my friends complain and wont log on this site. What would it take to make it a normal site? Should I just make this its own thread?

Quote from --Oz-- on June 4th, 2019, 12:14 AM

QUESTION: why is this website "Not Secure"? Most of my friends complain and wont log on this site. What would it take to make it a normal site? Should I just make this its own thread?

I'm also experiencing this very problem, but fortunately my fellow staff members are über savvy when it comes to handling these kinds of problems, so they'll be checking this out.

No the thread is just fine, just keep posting business as usual :-)

@ Patric1, for me to understand your optocoupler speedup circuit i had to redraw it :-D You might want to download a copy for yourself.
Question: is the 3906 (plus diode) section to act as a level sensitive trigger point (and this is where the speed come from)?

I looked up your output transistor, thats an oldie. My buddy in college went to work for national semiconductor, he started testing fets, I asked if he could get me some, he handed me the databook, yep, not datasheet, I just found an online copy, from 37 years ago! http://bitsavers.trailing-edge.com/components/national/_dataBooks/1982_National_Transistors_Databook.pdf

I was racing RC cars starting in 1980, in 81 the first electronic speed control came out with FET's. I picked the best high current - low RDSon fet in that databook, the good old IRFZ44 (44A 55V TO-220), i still have quite a few of them.

EDIT, I attached the Databook pdf, in case the link goes away.

Quote from --Oz-- on June 5th, 2019, 09:08 AM

http://bitsavers.trailing-edge.com/components/national/_dataBooks/1982_National_Transistors_Databook.pdf

Very awesome share, many thanks :thumbsup: