Calculates Q!
I don't know how accurate it is; I'll be testing some cases soon. It does include proximity and skin effects, which I think are both causing me grief just now.
-- John Larkin Highland Technology, Inc trk jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Very nice link. Thank you.
Interesting! Keep us posted as to accuracy. Thanks! ...Jim Thompson
-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
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I've had this in my bookmarks for about a decade, and have posted it many times here...
It is very accurate, more accurate than you can measure or wind a helix.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:
Is the Q value accurate?
--
Thanks,
- Win
Assumes circular conductor. Rectangular conductor as you have posted in rec ent images concentrates the current at the edges. This gives much higher sk in effect and greater losses. Try pancake inductor as I have suggested befo re. Unfortunately not handled by
A single-layer solenoid will fit on my board. #14 solid wire, about
0.5" x 1.5". That will leave a nice air gap between turns for cooling.I do need to explore the consequences of interaction with the PCB ground plane.
One other problem with the flat-winding Coilcraft, besides the proximity thing, is that the middle turns have essentially no cooling, so they get hot enough that the copper resistance increases a serious amount. It's almost thermal runaway.
The program predicts a Q of about 600 at 50 MHz for my solenoid, 4x better than the Coilcraft spec.
Where are my room-temp superconductors?
-- John Larkin Highland Technology, Inc trk jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
If you could buy room-temperature superconducting wires you could do cool party tricks like put a lil superconducting Thompson coil inside a glove with a LiPo battery and launch metal rings 100 feet in the air. "Hey check this out!" Pew!
As far as I know, yes. I don't have a fancy-shmancy Q-meter to verify.
Extensive discussion in the below-half of that page -- indulge if you have time!
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
recent images concentrates the current at the edges. This gives much higher skin effect and greater losses. Try pancake inductor as I have suggested b efore. Unfortunately not handled by
Much better. I'm glad you changed. I was not impressed with the Coilcraft p art. Great for DC, not so good for RF. It gets hot due to losses, mostly sk in effect. Got to keep the losses low. Ask any ham who has tried to make hi s own transmitting coils.
I just series resonate the L with a C and scope-probe things.
-- John Larkin Highland Technology, Inc trk jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
My customer keeps pushing us on pulse rate and voltage. The rev B board is OK at 2 MHz and 1200 volt pulses, but too many things are getting hot and he wants more. The inductors themselves could stand it, but the side effects of all that loss are terrible.
Manufacturing will not be enthusiastic about hand-winding and stripping and tinning solenoids from #14 magnet wire. Once I get it working, maybe I can find a coil winding shop in China or India to make me a bucket full. For some reason, Indians seem to be very good at magnetics.
Looks like rev C soon. This is becoming an obsession.
-- John Larkin Highland Technology, Inc trk jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On a sunny day (Tue, 03 Jul 2018 17:38:54 -0700) it happened John Larkin wrote in :
Ha, memories of old times, had coils similar number of turns on a ceramic former in the sixties driven by a PE1/100 tube at about 7 MHz. Same lighting up neons, then I put one in the coil and it exploded. So do not do that..., but if you must wear safety glasses. Also some RF transistors near it died.
How much power are you outputting? I tested with a 250W/220V photo bulb as dummy load.
Since I'm pulsing a capacitive load, my power output is technically zero. The DC input is running about 80 watts. That computes (scribbles furiously) to 0% efficiency.
I was wondering how fast a microwave oven magnetron starts up, so I put a NE-2 into one. It exploded in about 1 second.
-- John Larkin Highland Technology, Inc trk jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reactive power is power too...
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
in recent images concentrates the current at the edges. This gives much hig her skin effect and greater losses. Try pancake inductor as I have suggeste d before. Unfortunately not handled by
Where is you little pot of liquid nitrogen? Jsn Panteltje had one for his h igh temperature super-conductor coils.
A Stirling-engine based refrigerator will get you there, and won't take up much room.
t part. Great for DC, not so good for RF. It gets hot due to losses, mostly skin effect. Got to keep the losses low. Ask any ham who has tried to make his own transmitting coils.
You should be able to find a coil-winding shop closer to home.
Most enamelled copper wire is available with self-fluxing enamel - all you need to strip and tin it is a solder pot - which is a little iron pot which you fill with solder beofe you put on the close-fitting lid, which has a w ire-sized hole in the middle. Heat the pot of solder until the solder is mo lten, and stick the wire into the hole - it comes out stripped and tinned.
The coil winders at Cambridge Instruments had electrically heated pots, wit h a thermostat to keep the temperature a little aboe the melting point they were using.
Winding special purpose coils isn't a big deal.
-- Bill Sloman, Sydney
Everything you say is true. I have said equipment, plus a good supply of cores and bobbins, etc., but it's still a pain in the ass and I avoid it if possible. It wasn't so bad, when I had a good technician, who didn't complain about anything.
--
Thanks,
- Win
My next task is to wind a coil and measure its Q, and measure my existing Coilcraft parts for comparison. At a pulse rate of, say, 4 MHz, I need to know the Q at the fundamental and significant harmonics, so I can look at the FFT of the current waveform and trediously compute total power dissipation. I also need to evaluate the effects of PCB planes on inductor Q.
I'm thinking that I'll be seeing Qs from roughly 50 to 500.
I'm leaning towards parallel resonating the Ls at various frequencies and and measuring the resonance bandwidth. I can buy 0805 caps with Qs in the 2000 to 10,000 range.
The other ways might be
Pulse the LC and measure the exponential ringdown waveform with a good fet probe.
Drive a series LC, tune the frequency for input voltage null, and measure the loaded generator voltage. But the voltage would be very small, and the generator would need to have very small harmonic content. Most RF signal generators have horrible harmonic distortion.
Do the classic voltage multiplication thing. That might get tricky with Qs approaching 1000.
Maybe I'll just wind a new inductor and stick it into my pulse generator and see how it works. Avoid all that measuring and thinking.
-- John Larkin Highland Technology, Inc trk jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On a sunny day (Sat, 07 Jul 2018 11:03:53 -0700) it happened John Larkin wrote in :
You are using B = f0 / Q and Q = w.L/Rs ? And at those frequencies would not skin effect be important, silvered wire be better?
Q=1000 seems high to me, even Q=100...
Measuring bandwidth seems indeed the easiest way. Drive from a very high impedance (collector BJT out)
And then the Vce and Vcb are voltage dependent.... ooops
Seems a fun project.
You could also drive from a very low impedance in series like this:
Low Z power amp - [Rs] - L - C - ground
and measure voltage over C somehow, I have done that, HUGE voltages.... use bandwidth.
And if you use a step down transformer afer the driving power amp, say 10:1, then you have even lower series R and much lower voltages to work with.
Low Z power amp - 10:1 transformer - L --- C - ground ^ | scope | ground
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