John Larkin's LC oscillator
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From: dagmargoodboat on 11 Jun 2010 16:18 On Jun 11, 10:15 am, Jeroen Belleman <jer...(a)nospam.please> wrote: > John Larkin wrote: > > > I like the way it works with a very high turns ratio, very small AC > > drive at the emitter. But at lower ratios, it gets very nonlinear and > > becomes, if that means anything, a tuned blocking oscillator. The base > > capacitor value would be lowered so that the cap recharges a bunch > > during a oscillatory cycle. > > > I'm sure JT and JF will spend the next week diligently searching for a > > set of values that will make my circuit not work. Then they'll crow, > > or rather, cluck about it. That's OK: as Woody Allen says, we need the > > eggs. > > I made it squeg. Maybe that will please them. > > Jeroen Belleman Me too, esp. for lossy inductors. Increase the bias--that fixes it, for a number of reasons. -- Cheers, James Arthur
From: YD on 11 Jun 2010 16:43 Late at night, by candle light, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> penned this immortal opus: >On Fri, 11 Jun 2010 13:37:09 -0300, YD <ydtechHAT(a)techie.com> wrote: > >>Late at night, by candle light, Jeroen Belleman <jeroen(a)nospam.please> >>penned this immortal opus: >> >>>John Larkin wrote: >>>> >>>> I like the way it works with a very high turns ratio, very small AC >>>> drive at the emitter. But at lower ratios, it gets very nonlinear and >>>> becomes, if that means anything, a tuned blocking oscillator. The base >>>> capacitor value would be lowered so that the cap recharges a bunch >>>> during a oscillatory cycle. >>>> >>>> I'm sure JT and JF will spend the next week diligently searching for a >>>> set of values that will make my circuit not work. Then they'll crow, >>>> or rather, cluck about it. That's OK: as Woody Allen says, we need the >>>> eggs. >>> >>>I made it squeg. Maybe that will please them. >>> >> >>Yes, the tank's Q must be kept high. Increasing La's series R makes it >>squegg in a rather amusing way. Might be fun capturing it to a .wav. > >I always ran it with a big base capacitor. I'd expect that to prevent >squegging, as the tank resonance/rectification thing should be 1st >order, and 1st order loops are stable. A smaller base cap adds a >second time-variant element in the right ballpark. > >> >>JL: Can you recall ballpark the values of the inductors and associated >>frequencies in the physical circuit? High valued Ls tend to be rather >>resistive unless they're grossly oversized. > >Sorry, can't remember values after 35 years. > Ok, here's my take on it. It does seem to work class C, with some weird twists. The base is held practically constant, Q1 starts conducting when the emitter is pulled below Vb-.6V. As the tank gets close to Ve, there's a bit of suckage through bc, Vc ~= Ve. Then there's another bit of kick, Ve goes up and turns off Q1. Depending on turns ratio Vb stabilizes somewhere between 0.5 and -0.2V. A higher TR pulls it lower, makes sense. Adding about 1 or more ohms to L's Rs sets it squegging, haven't got that really figured yet. I start saving data after it has settled to make the currents easier resolved on the graph. Version 4 SHEET 1 880 680 WIRE 304 -64 16 -64 WIRE 432 -64 304 -64 WIRE 304 -32 304 -64 WIRE 400 -32 304 -32 WIRE 304 0 304 -32 WIRE 400 0 400 -32 WIRE 16 16 16 -64 WIRE 256 96 176 96 WIRE 304 96 304 64 WIRE 304 96 256 96 WIRE 400 96 400 80 WIRE 400 96 304 96 WIRE 176 144 176 96 WIRE 432 160 432 -64 WIRE 16 192 16 96 WIRE 64 192 16 192 WIRE 112 192 64 192 WIRE 208 240 176 240 WIRE 352 240 208 240 WIRE 16 256 16 192 WIRE 432 272 432 240 WIRE 352 304 352 240 WIRE 16 352 16 320 WIRE 352 416 352 384 FLAG 16 352 0 FLAG 352 416 0 FLAG 432 272 0 FLAG 256 96 c FLAG 64 192 b FLAG 208 240 e SYMBOL voltage 432 144 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL npn 112 144 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL ind2 384 -16 R0 SYMATTR InstName L1 SYMATTR Value 10m SYMBOL ind2 336 400 M180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L2 SYMATTR Value 25� SYMATTR SpiceLine Rser=30m SYMBOL res 0 0 R0 SYMATTR InstName R1 SYMATTR Value 100k SYMBOL cap 288 0 R0 SYMATTR InstName C1 SYMATTR Value 1� SYMATTR SpiceLine Rser=10m SYMBOL cap 0 256 R0 SYMATTR InstName C2 SYMATTR Value 1� SYMATTR SpiceLine Rser=10m TEXT 224 152 Left 0 !K1 L1 L2 1 TEXT -8 392 Left 0 !.tran 0 100m 5m TEXT 128 296 Left 0 !.opt plotwinsize 0 - YD. -- File corruption detected. Select option: 1 - Call the cops 2 - Call the press 3 - Bribe it Remove HAT if replying by mail.
From: BlindBaby on 11 Jun 2010 16:49 On Fri, 11 Jun 2010 12:28:41 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >Lotta munbling. What does it mean? What causes it? "Munbling"? I don't know... it is not a word that I am aware of. Since you were the one that used it, maybe you could tell us.
From: Tim Williams on 11 Jun 2010 17:24 "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message news:3mi416tp0q4m12qe3oiqnfllmalvd1h1vg(a)4ax.com... > I like the way it works with a very high turns ratio, very small AC > drive at the emitter. But at lower ratios, it gets very nonlinear and > becomes, if that means anything, a tuned blocking oscillator. The base > capacitor value would be lowered so that the cap recharges a bunch > during a oscillatory cycle. I did that in this circuit. Two stage though, since it has DC feedback. http://webpages.charter.net/dawill/tmoranwms/Circuits_2010/CC_Buck.png The feedback winding needs a very small voltage to keep the hysteresis band less than P-P current (i.e., keep it in CCM). Too small, of course, and it turns class C, then class A, then not oscillating at all, at which point it's just a boring two-diode-biased current source with extra parts. http://myweb.msoe.edu/williamstm/Images/CC_Buck1.jpg Despite the fairly large number of turns on the inductor, you can see it hardly takes any secondary at all to run. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: VWWall on 11 Jun 2010 17:30
John Larkin wrote: > On Fri, 11 Jun 2010 09:49:47 -0700, BlindBaby > <BlindMelonChitlin(a)wellnevergetthatonethealbumcover.org> wrote: > >> On Fri, 11 Jun 2010 09:14:34 -0700, John Larkin >> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>> On Fri, 11 Jun 2010 09:09:29 -0700, BlindBaby >>> <BlindMelonChitlin(a)wellnevergetthatonethealbumcover.org> wrote: >>> >>>> On Fri, 11 Jun 2010 08:37:43 -0700, John Larkin >>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>> On Fri, 11 Jun 2010 17:15:50 +0200, Jeroen Belleman >>>>> <jeroen(a)nospam.please> wrote: >>>>> >>>>>> John Larkin wrote: >>>>>>> I like the way it works with a very high turns ratio, very small AC >>>>>>> drive at the emitter. But at lower ratios, it gets very nonlinear and >>>>>>> becomes, if that means anything, a tuned blocking oscillator. The base >>>>>>> capacitor value would be lowered so that the cap recharges a bunch >>>>>>> during a oscillatory cycle. >>>>>>> >>>>>>> I'm sure JT and JF will spend the next week diligently searching for a >>>>>>> set of values that will make my circuit not work. Then they'll crow, >>>>>>> or rather, cluck about it. That's OK: as Woody Allen says, we need the >>>>>>> eggs. >>>>>> I made it squeg. Maybe that will please them. >>>>>> >>>>>> Jeroen Belleman >>>>> >>>>> Sloman is our resident squegging expert. >>>>> >>>>> John >>>> >>>> We should take a poll as to what attribute you are an expert in. >>>> >>>> I don't think it would result in the same determination that you >>>> obviously think it would. >>> Do you know what squegging means? Tell us. >> I have characterized a lot of oscillator circuits at the bench, John. >> Remember... power supplies... That was years ago. Now it is what the >> power supplies power. Still lots of oscillators though. >> >>> There are maybe two usages, both electronic, >> I have very little faith in your word derivative/origin declarations, >> John. That is aside from the fact that I am familiar with the word. >> Remember? I work in this industry. >> >>> but one of them is >>> obscure, >> Perhaps only in your thinking. >> >>> and the other is even more obscure. >> Certainly only in your thinking. > > Lotta munbling. What does it mean? What causes it? > Here's one for free: http://abmp3.com/download/5479684-squegging.html Or here's an application of a squegging oscillator: http://www.sm0vpo.com/rx/regenrx.htm -- Virg Wall, K6EVE |