1 Mhz Resonant Coil Setup

Home Help Search Login Register

Welcome,Guest. Please login or register.

OverUnity Research > Benches > Peterae (Moderator: Peterae) > 1 Mhz Resonant Coil Setup

2024-11-27, 04:47:39
News: If you have a suggestion or need for a new board title, please PM the Admins.
Please remember to keep topics and posts of the FE or casual nature.

Pages: 1 [2] 3

« previous next »

Author Topic: 1 Mhz Resonant Coil Setup (Read 38997 times)

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #25 on: 2010-11-02, 11:17:13 »
Group: Administrator Hero Member Posts: 3961	Hi WW No in fact thanks for the heads up. I hadn't even thought about the reactance values and certainly a good idea to calculate them. Just to be clever i thought i would use Don's suggested charts as i have the book at hand. I have attached a scan, with Don's desktop device against my device, it's interesting his device has much lower reactive Ohms. Peter PS i wonder how the ratio of primary reactance against the secondary reactance alter the performance of the energy transfer. If it would be possible to transfer the energy in the primary to a lower reactacne value in the secondary, i wonder if there would be a net power gain. It's also interesting that this should be an efficient method of transferring energy from one impedance circuit(Primary setup) to another impedance value system(secondary) without the normal mismatch losses. ------------------------ 1MhzReactanceChart.pdf (414.06 kB - downloaded 378 times.)

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #26 on: 2010-11-03, 15:30:13 »
Group: Administrator Hero Member Posts: 3961	OK tested and tweaked Coil and Oscillator Build 2 I am using a 18v Zener in place of the TVS and 1n4007 diodes this time. The coil on this one is a quarter of the wire length from coil 1 In operation it draws more current @25mA and i need to get a heat sink for the fet because as the temperature starts to rise slowly climbing the until an untimely death would occur. The coil get's hot after a while as well, and the feedback pickup has 3/4 of a turn. A few resistor value changes and an increase in the gate capacitor. The resonant frequency of this one is just above 1Mhz, i decided to use a 1n5 which brought it up to 1.14Mhz ------------------------ 1 Mhz Resonant Coil Setup 1MhzBuilt2.jpg (23.98 kB, 800x145 - viewed 1037 times.) 1 Mhz Resonant Coil Setup 1MhzOsc2.jpg (92.08 kB, 600x535 - viewed 1046 times.) « Last Edit: 2010-11-03, 20:35:56 by Peterae »

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #27 on: 2010-11-03, 20:40:41 »
Group: Administrator Hero Member Posts: 3961	A Technical question, my second builds primary is a quarter the wire length of my first build, is this why my circuit is drawing a lot more current or is it because i am not using the correct component values to bias and drive the gate properly. I notice my gate has a slightly larger sine on it than build one, i did try a pot and to get consistent oscillation it did require the resistor values i choose, maybe the pickup coil is still too much at 3/4 of a turn.

ion	Re: 1 Mhz Resonant Coil Setup « Reply #28 on: 2010-11-03, 22:02:49 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Quote from: Peterae on 2010-11-03, 20:40:41 A Technical question, my second builds primary is a quarter the wire length of my first build, is this why my circuit is drawing a lot more current or is it because i am not using the correct component values to bias and drive the gate properly. I notice my gate has a slightly larger sine on it than build one, i did try a pot and to get consistent oscillation it did require the resistor values i choose, maybe the pickup coil is still too much at 3/4 of a turn. Hi Peterae Your circuit has a resonant tank as the main coil. This will not perform as a blocking oscillator. It will perform as a nice class C oscillator. If you want this circuit to perform as a blocking oscillator, you will need more gate drive, not less. Also you would need to operate it without the tank capacitors. From the earlier pics, it looked like you barely had enough drive to force the gate high and low enough. looks like your FET is operating closer to Class A, hence the high power dissipation. If your output is a sine wave, you are not hitting the gate of the FET hard enough. The more you reduce the gate drive coil turns, the less drive you will have until it stops oscillating. Better to have a little extra drive, but adding resistance in series with the gate coil slows the circuit down. With the existing circuit arrangement, and at 1 MhZ there may be a limit to how fast you can charge and discharge the gate of the FET. The 47nF is sucking up all your drive current. I prefer a slightly different circuit arrangement with the drive coil not grounded. The coil instead is inserted between the gate and the bias network. This eliminates the 10nF cap. The placement of the 47nF is slowing the gates ability to swing. By re-arranging the circuit the gate will not "see" the 47nF except as part of a stiff bias supply. Keep the protection diodes close to the gate. If this is not clear, I'll try to supply a schematic. Sorry I didn't catch that 47nF problem before. Edit: OK posted the schematic. This is what I was getting at. Now the 47nF is in the proper place and not sucking base drive. Note: designators in my circuit are arbitrary and do not conform to yours. ------------------------ 1 Mhz Resonant Coil Setup Block Osc.jpg (14.67 kB, 391x275 - viewed 971 times.) 1 Mhz Resonant Coil Setup Blocking Osc wPOT.jpg (20.51 kB, 444x326 - viewed 1023 times.) « Last Edit: 2010-11-03, 22:51:59 by ION » --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #29 on: 2010-11-04, 10:46:28 »
Group: Administrator Hero Member Posts: 3961	Hello ION Thank you for the time you have given to this, i am sure there are many that will find this circuit invaluable for future experimentation. I will built it and post the details.

ion	Re: 1 Mhz Resonant Coil Setup « Reply #30 on: 2010-11-04, 12:22:46 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Quote from: Peterae on 2010-11-04, 10:46:28 Hello ION Thank you for the time you have given to this, i am sure there are many that will find this circuit invaluable for future experimentation. I will built it and post the details. Hi Peterae Let me explain the circuit a little further. The driving end of the coil, that is, the end connected to the gate now will "see" only the gate capacitance as a limiting factor. The end which you had grounded is now the biasing end and sits on a "virtual ground" as far as AC frequencies are concerned. The bias voltage (DC) is applied to this end via the voltage divider or pot. Keeping this end "stiff" with the 47nF to ground insures that all current generated by the drive coil is sent to the gate. What you need to decide is: Do you want the circuit to be a blocking oscillator (rectangular pulses out) or a resonant tank oscillator (sine wave) or some combination thereof? Typically, blocking oscillators are operated such that the driving transistor is fully on and fully off for each cycle. Also typically there is no resonant tank (LC) load, just the L. The circuit I posted shows no capacitors across the drain connected L, hence is a typical blocking oscillator. It will produce rectangular pulses at the drain of the FET. If a capacitor is added across the L. it becomes a resonant tank oscillator, and will produce a nearly pure sine wave at the drain of the FET. A resonant oscillator will drive the transistor less hard and the transistor will typically be biased inside the Class A region of an amplifier. If you try to drive the transistor harder, you will begin to distort the sine wave, and the circuit becomes a hybrid resonant tank / blocking oscillator. In any case, be sure to maintain proper polarity of the gate drive coil or the circuit may operate in a parasitic mode. Best of Luck --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #31 on: 2010-11-04, 13:09:20 »
Group: Administrator Hero Member Posts: 3961	Ok ION i see, my understanding of the Blocking oscillator was wrong in that case, i am after the tuned pure sine wave output across the primary coil, as you have posted an incredibly simple FET based pure sine oscillator i would like to explore and build your circuit and i am sure others will also follow. I have had some real good fun playing with the fet oscillator so far

ion	Re: 1 Mhz Resonant Coil Setup « Reply #32 on: 2010-11-04, 13:21:04 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	There is another form of this resonant tank oscillator called the "tuned plate-tuned grid" oscillator from vacuum tube days. In this case the resonant tank is calculated for the desired frequency and a small variable tuning capacitor is placed across the gate drive coil in order to tune it and allow it to "resonate' at the same frequency. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #33 on: 2010-11-05, 10:57:55 »
Group: Administrator Hero Member Posts: 3961	I have now connected my secondary caps and trimmers to each secondary coil. Here's a snap of the setup And here's a video of me pulling the primary in and out of the 2 secondary coils, each secondary is being scoped on chan 1 and 2 The scope is set to 100V/Div [youtube]http://www.youtube.com/watch?v=3VYZiXYwruU[/youtube] ------------------------ 1 Mhz Resonant Coil Setup 1MhzSecondary2.JPG (53.32 kB, 600x450 - viewed 2752 times.)

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #34 on: 2010-11-05, 11:06:30 »
Group: Administrator Hero Member Posts: 3961	@ ION Would you know if it's possible to have a fet oscillator that uses the LC to set the resonant frequency of the oscillator but does not require the pickup coil for feedback. Maybe a capacitor coupled to the drain as feedback? Thanks Peter

ion	Re: 1 Mhz Resonant Coil Setup « Reply #35 on: 2010-11-05, 12:24:50 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	The criteria for an oscillator is that you need a gain > 1 in the amplifier and >180 degrees of phase shift, which the pickup coil provides. Your pickup coil can be located some distance from the resonant tank, since the tank will be transmitting to the pickup coil so this should not be a problem. You might need more turns on the pickup coil if it is located a distance from the tank as the drive signal will fall off with distance and you need to replace the lost voltage gain. Also tuning the pickup coil with a small variable cap will up the gain. Note also that physical orientation will change the phase of the pickup coil so be sure to keep the vertical polarization of the coils in alignment. If you absolutely must eliminate the pickup coil, you might consider a colpitts oscillator, a phase shift oscillator if you have enough gain in the circuit, or a Wein bridge. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

ion	Re: 1 Mhz Resonant Coil Setup « Reply #36 on: 2010-11-05, 12:35:31 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Quote @ ION Would you know if it's possible to have a fet oscillator that uses the LC to set the resonant frequency of the oscillator but does not require the pickup coil for feedback. Maybe a capacitor coupled to the drain as feedback? Thanks Peter A capacitor from the drain probably will not work, as it does not provide the required phase shift, it is negative feedback instead of positive feedback The criteria for an oscillator is that you need a gain > 1 in the amplifier and >180 degrees of phase shift, which the pickup coil provides. Your pickup coil can be located some distance from the resonant tank, since the tank will be transmitting to the pickup coil, so this should not be a problem. You might need more turns on the pickup coil if it is located a distance from the tank as the drive signal will fall off with distance and you need to replace the lost voltage gain. Also tuning the pickup coil with a small variable cap will up the gain. Note also that physical orientation will change the phase of the pickup coil so be sure to keep the vertical polarization of the coils in alignment. If you absolutely must eliminate the pickup coil, you might consider a colpitts oscillator, a phase shift oscillator if you have enough gain in the circuit, or a Wein bridge. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #37 on: 2010-11-05, 13:16:10 »
Group: Administrator Hero Member Posts: 3961	Just an idea ION, i was not sure if it was possible Thanks for your reply anyway. I have now added a diode of each end of each secondary as in Don's table top and these feed a 2uF cap, i then use a 90V spark gap to drive a 12V 5 Watt bulb, the gap fires like mad the bulb does light but not very brightly. Psu was set to 125V @35mA 4.375 Watts SG is on left and bulb filament on right [youtube]http://www.youtube.com/watch?v=YHmtAEU1rgQ[/youtube]

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #38 on: 2010-11-05, 13:32:40 »
Group: Administrator Hero Member Posts: 3961	Phase shift oscillator seems to require RC for timing, but the Colpitts uses the capacitor but center tapped, now this is interesting. but then the article goes on to say biasing resistors are needed

ion	Re: 1 Mhz Resonant Coil Setup « Reply #39 on: 2010-11-05, 13:44:37 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Those circuits get messy, if you've got a lot of time and FET's in you parts bin you might get something working. I think the circuit you now have or the ones I supplied are the cleanest approach. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #40 on: 2010-11-05, 13:59:38 »
Group: Administrator Hero Member Posts: 3961	OK ION thanks for the advice, i will soon build your circuit up as my build2 is proving temperature dependent.Doesn't always start from cold.

ion	Re: 1 Mhz Resonant Coil Setup « Reply #41 on: 2010-11-05, 14:07:19 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	It is a good idea to make sure you've got the voltage divider for the FET bias worked out. I prefer to temporarily replace the resonant tank with a resistor, say 10 K, then make sure the divider has been worked out to supply the required 2 to 8 volts to the FET gate. This is why a potentiometer is better as you can precisely adjust the turn on threshold of the gate. The divider string will change as supply voltage changes, so if you plan on a lot of different voltages, best to zener regulate the divider. I'll put together a good circuit I have tested. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #42 on: 2010-11-05, 14:14:38 »
Group: Administrator Hero Member Posts: 3961	I fully understand what you are saying, the regulated reference supply for the pot shouldn't be needed for me as i will always use 125V, i will use a pot, i could even leave the pot in circuit this time.

ion	Re: 1 Mhz Resonant Coil Setup « Reply #43 on: 2010-11-05, 14:27:15 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Here's a preferred circuit. Actually R2 can be much lower than 100K, low enough to bias up the Zener to 10 volts. ------------------------ 1 Mhz Resonant Coil Setup Tuned Plate Tuned Grid.jpg (26.89 kB, 485x294 - viewed 762 times.) --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #44 on: 2010-11-05, 14:52:13 »
Group: Administrator Hero Member Posts: 3961	That is a pretty handy circuit ION thanks for sharing with us

ion	Re: 1 Mhz Resonant Coil Setup « Reply #45 on: 2010-11-05, 15:08:33 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Quote from: Peterae on 2010-11-05, 13:16:10 Just an idea ION, i was not sure if it was possible Thanks for your reply anyway. I have now added a diode of each end of each secondary as in Don's table top and these feed a 2uF cap, i then use a 90V spark gap to drive a 12V 5 Watt bulb, the gap fires like mad the bulb does light but not very brightly. Psu was set to 125V @35mA 4.375 Watts SG is on left and bulb filament on right [youtube]http://www.youtube.com/watch?v=YHmtAEU1rgQ[/youtube] Interestingly, the youtube link does not show up in your post #37, but shows in the quoted text, only before I save the quote, then it disappears. I copied it out of the text quote, here it is. Seems to be a glitch in the program. http://www.youtube.com/watch?v=YHmtAEU1rgQ As a control maybe take some light meter measurements of your bulb at various power levels directly off your power supply. I like to use a distance of one meter through a darkened cardboard tube. You now have a calibrated light source. Then hook up to your circuit and using the light meter / tube again and you can reference the power level output versus input. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #46 on: 2010-11-05, 16:00:00 »
Group: Administrator Hero Member Posts: 3961	That is strange shows for me ok in my post, anyone else having trouble.

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #47 on: 2010-11-05, 16:22:57 »
Group: Administrator Hero Member Posts: 3961	I've had a few hours playing with my build so far today. I ended up driving a 2.4V bulb in series with a 90V Spark gap, it's quiet bright, i added another 10uF cap to the cap bank bringing in a total of 13uF now, the bulb then flashes at a number of hertz(Difficult to judge), but this gives me an indication of how much energy the tuned system is provided to the bulb, all i need do is change tuning and config to look for faster flashes which inturn would indicate more captured energy from the system. I have not done any calcs, but it is definitively way under unity. I have tried all sorts of coil cap configs and can conclude as follows. 2 tuned secondary's do not provide as much power as 1 tuned secondary no matter how much you play with the primary position and tuning of both secondary's, i believe the reason for this is that when 2 identically tuned coils are placed next to each other they will inherently pull each resonant frequency away from the tuned primary frequency. This actually is quiet interesting because when you scope the 2 unloaded secondaries there's equal potential in each secondary, so if you can draw 1 watt from one secondary what do we need to do to draw 1 watt from the other at the same time and add this together to get 2 watts.What ever the answer i could not do it. I tried one secondary with series capacitive inductive resonance and it made no addition to the net energy whats so ever. I tried one secondary with no tuning at all as in Don's bench top coil with no cap and again it appeared to make no more gain to the net energy whats so ever. Not sure where to go with this, maybe tune one secondary to a harmonic on the other secondary

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #48 on: 2010-11-05, 18:12:31 »
Group: Administrator Hero Member Posts: 3961	Quote 2 tuned secondary's do not provide as much power as 1 tuned secondary no matter how much you play with the primary position and tuning of both secondary's, i believe the reason for this is that when 2 identically tuned coils are placed next to each other they will inherently pull each resonant frequency away from the tuned primary frequency. This actually is quiet interesting because when you scope the 2 unloaded secondaries there's equal potential in each secondary, so if you can draw 1 watt from one secondary what do we need to do to draw 1 watt from the other at the same time and add this together to get 2 watts.What ever the answer i could not do it. maybe 2 tuned secodaries just introduce more losses to the system hence less output

Peterae	Re: 1 Mhz Resonant Coil Setup « Reply #49 on: 2010-11-10, 18:28:35 »
Group: Administrator Hero Member Posts: 3961	If i build a coil tuned to the 3rd harmonic of my 1Mhz driver coil, will it resonate at the 3rd harmonic, if not what do i need to do to get it to. I tried just the trimmer across my secondary coil, using math i worked out it should resonate at the twice the frequency, but it didnt, all i had was the 1mhz imposed from my primary? Do i need to drive the primary using a square wave or something.

Pages: 1 [2] 3

« previous next »

Home Help Search Login Register

Theme © PopularFX | Based on PFX Ideas! | Scripts from iScript4u

2024-11-27, 04:47:39

SMF 2.0.18 | SMF © 2021, Simple Machines
XHTML
RSS
WAP2