On Jan 15, 7:42=A0pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Sun, 15 Jan 2012 10:11:07 -0800 (PST), Bill Sloman
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> <bill.slo...@ieee.org> wrote:
> >On Jan 15, 6:06=A0pm, John Larkin
> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >> On Sun, 15 Jan 2012 02:25:49 -0800 (PST), Bill Sloman
>
> >> <bill.slo...@ieee.org> wrote:
> >> >On Jan 15, 4:21=A0am, John Larkin
> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >> >> On Sat, 14 Jan 2012 18:03:56 -0800 (PST), Bill Sloman
>
> >> >> <bill.slo...@ieee.org> wrote:
> >> >> >On Jan 15, 12:05=A0am, John Larkin
> >> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >> >> >> On Sat, 14 Jan 2012 14:50:38 -0800 (PST),BillSloman
>
> >> >> >> <bill.slo...@ieee.org> wrote:
> >> >> >> >On Jan 14, 10:25=A0pm, John Larkin
> >> >> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >> >> >> >> On Sat, 14 Jan 2012 10:59:47 -0800 (PST),BillSloman
>
> >> >> >> >> <bill.slo...@ieee.org> wrote:
> >> >> >> >> >On Jan 14, 7:16=A0pm, John Larkin
> >> >> >> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >> >> >> >> >> On Sat, 14 Jan 2012 03:00:55 -0800 (PST),BillSloman
>
> >> >> >> >> >> <bill.slo...@ieee.org> wrote:
> >> >> >> >> >> >On Jan 14, 11:09=A0am, John Devereux <j...@devereux.me.uk=
> wrote:
> >> >> >> >> >> >> BillSloman<bill.slo...@ieee.org> writes:
> >> >> >> >> >> >> > On Jan 14, 5:36=A0am, John Larkin
> >> >> >> >> >> >> > <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >> >> >> >> >> >> >> On Fri, 13 Jan 2012 17:44:04 -0800 (PST),BillSloman
>
> >> >> >> >> >> >> >> <bill.slo...@ieee.org> wrote:
> >> >> >> >> >> >> >> >The Baxandall parallel class-D oscillator "squegs" =
in real life if you
> >> >> >> >> >> >> >> >build it with a high value inductance in the curren=
t feed and bipolar
> >> >> >> >> >> >> >> >switches. An LTSpice circuit using the Gummel-Poon =
model for the
> >> >> >> >> >> >> >> >bipolar transistors doesn't show this - it settles =
down to a stable
> >> >> >> >> >> >> >> >sinusoidal oscillation within less than a hundred c=
ycles.
>
> >> >> >> >> >> >> >> >The obvious effect of using a high value inductor i=
s that the current
> >> >> >> >> >> >> >> >through the inductor over-shoots dramatically at st=
art-up and actually
> >> >> >> >> >> >> >> >reverses polarity as it recovers, so the bipolar tr=
ansistors briefly
> >> >> >> >> >> >> >> >run inverted (emitter and collector diffusions swap=
roles). In real
> >> >> >> >> >> >> >> >life this clearly makes the circuit =A0behave very =
oddly, but the Gummel-
> >> >> >> >> >> >> >> >Poon model equally clearly doesn't capture this par=
ticular oddness.
>
> >> >> >> >> >> >> >> >VBIC might do better, but it doesn't with the model=
parameters that
> >> >> >> >> >> >> >> >I =A0bodged out of Gummel-Poon parameters. Somebody=
who had a better -
> >> >> >> >> >> >> >> >some - understanding of the VBIC parameters might w=
ell be able to do
> >> >> >> >> >> >> >> >better.
>
> >> >> >> >> >> >> >> It seems to wobble a bit on startup, but doesn't act=
ually squeg even
> >> >> >> >> >> >> >> with a full henry as the feed inductor.
>
> >> >> >> >> >> >> > That's what I'm complaining about. A real circuit wou=
ld almost
> >> >> >> >> >> >> > certainly squeg.
>
> >> >> >> >> >> >> Well there's one way to find out isn't there? :)
>
> >> >> >> >> >> >The last one I built with an over-sized oscillator (which=
was the
> >> >> >> >> >> >first one I ever built, more than forty years ago) certai=
nly squegged.
> >> >> >> >> >> >Building another just to prove the point would be somethi=
ng of a waste
> >> >> >> >> >> >of time.
>
> >> >> >> >> >> If the behavior of this oscillator is a waste of time, giv=
e it up.
>
> >> >> >> >> >> If it were interesting to me, I'd have one running in abou=
t 30
> >> >> >> >> >> minutes, on a handsome, dremeled, labeled slice of copperc=
lad.
>
> >> >> >> >> >A bit extravagant for a 16kHz oscillator. If I get enthusias=
tic enough
> >> >> >> >> >to build one I'll put it on a perforated prototyping board. =
I rather
> >> >> >> >> >like the one Farnell sells that comes with a "collander grou=
nd plane"
> >> >> >> >> >on the component side of the board. The copper rings around =
the holes
> >> >> >> >> >on the track side can be chopped up to support surface mount=
parts if
> >> >> >> >> >you want to mix and match.
>
> >> >> >> >> >It will take a bit longer than half an hour - winding transf=
ormers is
> >> >> >> >> >tedious, even when you've got access to a coil winding machi=
ne.
>
> >> >> >> >> You can wind a pot core in a few minutes, by hand.
>
> >> >> >> >I know. I've done it. It doesn't have to take long to be tediou=
s.
>
> >> >> >> >>ftp://jjlarkin.lmi.net/Z206_pcb.JPG
>
> >> >> >> >> Or buy one of those dual-winding inductors for about a dollar=
.
>
> >> >> >> >Any particular "dual-winding" inductor? It's not a name I'm fam=
iliar
> >> >> >> >with. As far as I'm concerned, any inductor carrying two or mor=
e
> >> >> >> >separate but magnetically linked windings is either a transform=
er or a
> >> >> >> >common mode choke.
>
> >> >> >> Things like this:
>
> >> >> >>http://search.digikey.com/us/en/products/DRQ74-220-R/513-1148-6-N=
D/19...
>
> >> >> >> People call these dual-winding inductors, probably because they =
are
> >> >> >> characterized to carry a lot of DC current. Of course they work =
nicely
> >> >> >> as transformers.
>
> >> >> >It's the first time I've heard of it being called a dual-winding
> >> >> >inductor. There one in my Peltier thermostat paper
>
> >> >> >Sloman A.W., Buggs P., Molloy J., and Stewart D. =93A microcontrol=
ler-
> >> >> >based driver to stabilise the temperature of an optical stage to 1=
mK
> >> >> >in the range 4C to 38C, using a Peltier heat pump and a thermistor
> >> >> >sensor=94 Measurement Science and Technology, 7 1653-64 (1996)
>
> >> >> >I called it a balun on page 1663 and in Figure 8. The - English -
> >> >> >supplier called it a common mode choke.
>
> >> >> >> I used their big brothers in a power supply that we discussed he=
re a
> >> >> >> while back.
>
> >> >> >Lots of people do.
>
> >> >> >>ftp://jjlarkin.lmi.net/ESM_power.pdf
>
> >> >> >T1 and T2?
>
> >> >> I used them as transformers so I called them transformers. PADS let=
s
> >> >> you do that.
>
> >> >> The other reason they are called "inductors" is that they have a
> >> >> specified inductance and tolerance. Transformers are seldom specifi=
ed
> >> >> for inductance, and seldom specified for their DC current capacity.
>
> >> >> It really doesn't matter what you call them.
>
> >> >Unless you want other people to know what you are talking about.
>
> >> We follow proper conventions for reference designators. A resistor is
> >> R1, not RN1 or RV1 or POT1. A transistor is Q, not T or TR or TRN or
> >> any of that nonsense. Since thess parts look like a transformer [1] on
> >> the schematic and act like a transformer, I called them T on the
> >> schematic. When we use these as inductors, we put the windings in
> >> series or in parallel and call them L.
>
> >> [1] except that they have two cores. That's because the part was
> >> created as two inductors, and we plopped them alongside one another to
> >> make it look like a transformer.
>
> >> >> What you call them
> >> >> shouldn't constrain what you are willing to use them for.
>
> >> >Obviously.
>
> >> >> You could
> >> >> use these as baluns, common-mode chokes, inductors, power
> >> >> transformers, signal transformers, flyback transformers, resistors,=
or
> >> >> RTDs. Nice little parts.
>
> >> >They are a bit bulky for use as resistors and RTDs. The bulk might be
> >> >useful if you wanted to dissipate a significant amount of power, but
> >> >it strikes me as an expensive way of getting it.
>
> >> If you allow yourself to think, more opportunities are available. Add
> >> "gain control device" to the list. Maybe even "delay line."
>
> >With two coils you could use one as a "saturable reactor"
>
> >http://en.wikipedia.org/wiki/Saturable_reactor
>
> Probably not practical with this series of parts. They typically hit a
> thermal/current limit before magnetic saturation.
>
>
>
> >I've never seen it done. and would have thought - as the wikipedia
> >article does - that the approach is close to obsolete.
>
> It never hurts to understand what parts can do.
>
>
>
> >You can build up delay lines out of all sorts of RLC components. I
> >hadn't realised that common mode chokes had anything special to offer
> >as the inductive components in such a synthesis.
>
> >http://jcatsc.com/media/TechnicalReports/02-CoupledInductorDelayFilte...
>
> Since it's probably bifalar wound, maybe its windings could be used as
> a twisted-pair transmission line, a delay line all on their own.
Some are bifilar wound, some not. The length of the winding - and thus
the delay - isn't something the manufacturer specifies all that
tightly on the data sheet, and might change without notice if they
changed core materials.
Probably not the ideal building block.
--
Bill Sloman, Nijmegen