On Sun, 15 Jan 2012 10:11:07 -0800 (PST), Bill Sloman
bill.slo...@ieee.org> wrote:
On Jan 15, 6:06 pm, 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 am, 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 am, 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 pm, 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 pm, 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 am, John Devereux <j...@devereux.me.uk> wrote:
BillSloman<bill.slo...@ieee.org> writes:
On Jan 14, 5:36 am, 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 current 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 cycles.
The obvious effect of using a high value inductor is that the current
through the inductor over-shoots dramatically at start-up and actually
reverses polarity as it recovers, so the bipolar transistors briefly
run inverted (emitter and collector diffusions swap roles). In real
life this clearly makes the circuit behave very oddly, but the Gummel-
Poon model equally clearly doesn't capture this particular oddness.
VBIC might do better, but it doesn't with the model parameters that
I bodged out of Gummel-Poon parameters. Somebody who had a better -
some - understanding of the VBIC parameters might well be able to do
better.
It seems to wobble a bit on startup, but doesn't actually squeg even
with a full henry as the feed inductor.
That's what I'm complaining about. A real circuit would 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) certainly squegged.
Building another just to prove the point would be something of a waste
of time.
If the behavior of this oscillator is a waste of time, give it up.
If it were interesting to me, I'd have one running in about 30
minutes, on a handsome, dremeled, labeled slice of copperclad.
A bit extravagant for a 16kHz oscillator. If I get enthusiastic 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 ground 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 transformers is
tedious, even when you've got access to a coil winding machine.
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 tedious.
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 familiar
with. As far as I'm concerned, any inductor carrying two or more
separate but magnetically linked windings is either a transformer or a
common mode choke.
Things like this:
http://search.digikey.com/us/en/products/DRQ74-220-R/513-1148-6-ND/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. “A microcontroller-
based driver to stabilise the temperature of an optical stage to 1mK
in the range 4C to 38C, using a Peltier heat pump and a thermistor
sensor” 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 here 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 lets
you do that.
The other reason they are called "inductors" is that they have a
specified inductance and tolerance. Transformers are seldom specified
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
