John Larkin's LC oscillator
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From: Jasen Betts on 12 Jun 2010 04:51 On 2010-06-11, Robert Baer <robertbaer(a)localnet.com> wrote: > YD 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. >> >> 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. >> >> - YD. >> > In fact, it would be interesting to know how to "resonate" an > inductor that has a lot of (internal) resistance. add external negative resistance. --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: John Larkin on 12 Jun 2010 10:57 On Sat, 12 Jun 2010 08:53:20 +0100, John Devereux <john(a)devereux.me.uk> wrote: >John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> writes: > >> On Fri, 11 Jun 2010 17:43:39 -0300, YD <ydtechHAT(a)techie.com> wrote: >> >>>Late at night, by candle light, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> penned this immortal >>>opus: > >[...] > >> >> That's nice. It's running pretty hard class C. >> >> Try this: >> >> C2 = 10 uF >> L2 = 0.25 uH >> >> That will move it to class A, with about 50 millivolts p-p drive at >> the emitter. That's more like what I had in mind originally. Vb is >> stiff at about +0.6, and Vc dips down to about -0.1, a little below >> Ve, sucking a brief blip of current out of the base cap. The sine wave >> is just slightly flattened on the bottom. >> >> It's useful to add a small resistor, like 1 milliohm, in the emitter >> so that you can probe the current. It's interesting. > >Hi John, > >You don't need to add the the resistor. You can just measure the emitter >current by clicking on it! > I couldn't get that to work. Maybe my aim isn't good enough. John
From: Archimedes' Lever on 12 Jun 2010 11:04 On 12 Jun 2010 08:39:10 GMT, Jasen Betts <jasen(a)xnet.co.nz> wrote: >On 2010-06-11, BlindBaby <BlindMelonChitlin(a)wellnevergetthatonethealbumcover.org> wrote: >> On Fri, 11 Jun 2010 08:16:29 -0500, John Fields >><jfields(a)austininstruments.com> wrote: >> >... >>>SYMBOL res -400 256 R0 >>>SYMATTR InstName R2 >>>SYMATTR Value 100k >>>SYMBOL res -512 160 R0 >>>SYMATTR InstName R3 >>>SYMATTR Value 1000 >>>SYMBOL cap -128 304 R0 >>>SYMATTR InstName C2 >>>SYMATTR Value 1e-7 >>>SYMBOL res 0 320 R0 >>>SYMATTR InstName R4 >>>SYMATTR Value 750 >>>TEXT 32 184 Left 0 !K1 L1 L2 1 >>>TEXT -528 464 Left 0 !.tran 5 >>>TEXT -528 496 Left 0 !.wave .\\bong.wav 8 10000 N008 >> >> LT doesn't like all the SYMATTR use. It expects to only see it once. > >Works fine here. version 4.07q > >--- news://freenews.netfront.net/ - complaints: news(a)netfront.net --- I chose the wrong extension to name the file with.
From: Baron on 12 Jun 2010 12:30 John Larkin Inscribed thus: > On Fri, 11 Jun 2010 10:38:51 -0700, Robert Baer > <robertbaer(a)localnet.com> wrote: > >>BlindBaby 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. >> Well, now, if both usages are NOT obscure (and i know of only one >> and >>have been a tech for at least 50 years),please TELL US the source / >>creation of the word and the context in each case. >> That way we will know that you are not just doing a fantasy trip. > > Everybody must know the less obscure case by now. > > The more obscure case: In the toob days, sometimes TV sets would have > vertical bars on the screen. It was caused by Barkhausen oscillations > in the horiz output tube, getting back into the RF input. Some TV > techs called that "squegging." > > I have no idea of the source of the word. > > John I've always thought (a burst of oscillations at regular intervals) probably from the sound made when a radio squegs. -- Best Regards: Baron.
From: John Fields on 12 Jun 2010 16:28
On Fri, 11 Jun 2010 20:04:42 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Fri, 11 Jun 2010 08:16:29 -0500, John Fields ><jfields(a)austininstruments.com> wrote: > >The .wav thing is cute. But the ringdown is being caused by the LC's >Q, not by the transistor oscillation. The R2-C4 thing dies out pretty >soon, and then the tank rings on its own. That why you need R4; at >infinite Q, it would ring forever. > >If you can get an LC with a Q that high, you can simulate a nice bell >noise by just whacking it and letting it ring... like a real brass >bell. Much simpler. --- Speaking of real world parts and more-or-less realistic bong frequencies, L1 here is a Caddell-Burns 5.6mH 2.9 ohm choke (P/N 7200-34), C1 is 10�F with an ESR of an ohm or less, and the thing oscillates at about 675Hz. Version 4 SHEET 1 936 680 WIRE -864 48 -1072 48 WIRE -800 48 -864 48 WIRE -576 48 -704 48 WIRE -448 48 -576 48 WIRE -352 48 -448 48 WIRE -448 64 -448 48 WIRE -352 64 -352 48 WIRE -864 96 -864 48 WIRE -576 96 -576 48 WIRE -928 144 -976 144 WIRE -448 160 -448 128 WIRE -352 160 -352 144 WIRE -352 160 -448 160 WIRE -976 176 -976 144 WIRE -1072 192 -1072 48 WIRE -752 192 -752 112 WIRE -752 192 -864 192 WIRE -448 192 -448 160 WIRE -576 240 -576 176 WIRE -512 240 -576 240 WIRE -864 272 -864 192 WIRE -752 272 -752 192 WIRE -976 288 -976 256 WIRE -576 304 -576 240 WIRE -448 320 -448 288 WIRE -352 320 -448 320 WIRE -448 336 -448 320 WIRE -352 336 -352 320 WIRE -1072 432 -1072 272 WIRE -976 432 -976 368 WIRE -976 432 -1072 432 WIRE -864 432 -864 352 WIRE -864 432 -976 432 WIRE -752 432 -752 336 WIRE -752 432 -864 432 WIRE -576 432 -576 368 WIRE -576 432 -752 432 WIRE -448 432 -448 416 WIRE -448 432 -576 432 WIRE -352 432 -352 416 WIRE -352 432 -448 432 WIRE -1072 528 -1072 432 FLAG -1072 528 0 SYMBOL ind2 -368 48 R0 SYMATTR InstName L1 SYMATTR Value 5.6e-3 SYMATTR Type ind SYMATTR SpiceLine Rser=2.9 SYMBOL ind2 -368 432 M180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L2 SYMATTR Value 500e-6 SYMATTR Type ind SYMATTR SpiceLine Rser=.1 SYMBOL npn -512 192 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL res -592 80 R0 SYMATTR InstName R1 SYMATTR Value 100k SYMBOL cap -464 64 R0 SYMATTR InstName C1 SYMATTR Value 10e-6 SYMATTR SpiceLine Rser=1 SYMBOL cap -592 304 R0 SYMATTR InstName C2 SYMATTR Value 1e-7 SYMBOL voltage -1072 176 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 3 24 104 Invisible 0 SYMATTR Value 5 SYMATTR InstName V1 SYMBOL pnp -928 192 M180 SYMATTR InstName Q2 SYMATTR Value 2N4403 SYMBOL voltage -976 272 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 3 24 104 Invisible 0 SYMATTR Value PULSE(5 0 0 1e-6 1e-6 .01) SYMATTR InstName V3 SYMBOL npn -800 112 R270 SYMATTR InstName Q3 SYMATTR Value 2N3904 SYMBOL cap -768 272 R0 SYMATTR InstName C3 SYMATTR Value 7.5e-6 SYMBOL res -880 256 R0 SYMATTR InstName R2 SYMATTR Value 2e6 SYMBOL res -992 160 R0 SYMATTR InstName R3 SYMATTR Value 1000 SYMBOL res -464 320 R0 SYMATTR InstName R4 SYMATTR Value 1000 TEXT -432 184 Left 0 !K1 L1 L2 1 TEXT -1048 464 Left 0 !.tran 2.5 uic TEXT -1048 496 Left 0 !.wave .\\bong.wav 8 10000 N008 JF |