Searching \ for '[EE]: Winding inductor for 2 trans. LED blinker' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/displays.htm?key=led
Search entire site for: 'Winding inductor for 2 trans. LED blinker'.

Exact match. Not showing close matches.
PICList Thread
'[EE]: Winding inductor for 2 trans. LED blinker'
2002\10\19@171750 by David & Ann Scott

flavicon
face
This circuit from the SMPS circuit challenge of a year ago(!) is the "LED
blinker/dead battery milker/3909 replacement" from Russell McMahon:

www.piclist.com/postbot.asp?id=piclist\2001\10\10\084451a
http://www.piclist.com/postbot.asp?id=piclist\2001\09\27\023449a

It uses an RF choke of 300 uH.  I've spent hours trying to figure out how to
wind this inductor myself.  Alot of info is available
(http://www.mag-inc.com/library.asp#top, http://www.ferroxcube.com/ and
others) but it's hard for me to tell which is relevant or not.

It appears an aircoil would require 300+ turns which my guess is not
practical (and will other properties of the coil be correct?).  [ L = (A^2.
x N^2) / (9A + 10B) ]

Should a core be used?  What type?  Could some type of toroid be used (kids
might like winding it??).  What formulas can I use for this application?
Are any of the design guides applicable?  (There seem to be alot of info for
designing SMPSs but this application seems to be on the fringe.)

A similar application (http://www.emanator.demon.co.uk/bigclive/joule.htm)
uses a ferrite bead.  Can that be used?

Thanks.
---
David  Scott
http://www.piclist.com/member/DS-sss-C40
PIC/PICList FAQ: http://www.piclist.com

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2002\10\19@182205 by Peter L. Peres

picon face
Determining inductance and turns for unknown cores is a problem without
instruments. The aircoil will do it right but as you said, it is too
large.

You can buy off the shelf 300uH inductors. They are ready for use.

To determine a toroid or other core's parameters you need a RLC bridge or
at least an inductance meter. Even so you will not know for sure if it's a
filter (dispersive) core or a good high Q core, and what it will do when
it will have dc bias through it.

A simple RL bridge can be improvised like so:

12Vac -(A)---Lx--(B)--R--(C)- 12Vac'

R = 10 Ohms 20W (but you will use it for a short time).

For L~= 300uH you would measure about 0.135Vac between A and B. The 12V
comes from an ordinary transformer (110->12V ac, 1.5A). The coil must
withstand 1.5A current. For high Al toroids this could not be so. Higher
voltage = higher inductance, lower voltage the other way around.

hope this helps,

Peter

(The formula used was Zl = 2*pi*f*L and Zcircuit = sqrt(R^2 + Zl^2) where
R was chosen ~= 100 times Zl to reduce errors)

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2002\10\19@182413 by Peter L. Peres

picon face
Oops I forgot something important:

You need to connect the circuit to a DC 12V source too, and read the AB
voltage in DC, then when measuring in AC substract this voltage from the
readout, otherwise the readout will be way off imho. This is due to the dc
resistance of the coil. The method above removes the dc resistance (well,
almost), from the end result.

Peter

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2002\10\19@183240 by Dwayne Reid

flavicon
face
Why not have a look at Clive Mitchell's version: his uses a single
transistor and he includes pictures of how to use a ferrite bead to make
the inductor.  Have a look at
<http://www.emanator.demon.co.uk/bigclive/joule.htm>

dwayne

At 04:14 PM 10/19/02 -0500, David & Ann Scott wrote:
>This circuit from the SMPS circuit challenge of a year ago(!) is the "LED
>blinker/dead battery milker/3909 replacement" from Russell McMahon:


--
Dwayne Reid   <spam_OUTdwaynerTakeThisOuTspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 18 years of Engineering Innovation (1984 - 2002)
 .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-
    `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
commercial email nor is intended to solicit commercial email.

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2002\10\19@235519 by David & Ann Scott

flavicon
face
> From: Peter L. Peres
> Determining inductance and turns for unknown cores is a problem without
> instruments. The aircoil will do it right but as you said, it is too
> large.
>
> You can buy off the shelf 300uH inductors. They are ready for use.

I don't have any cores - unknown or known.  I would like to buy what I need
but don't know where to start (seems they come in a wide array of shapes,
sizes, types & materials).  I've used the RF chokes (J.W. Miller) from
DigiKey but would like to know how to wind my own.  The RLC circuit for
checking will be useful though.  Thanks Peter.

> From: Dwayne Reid
> Why not have a look at Clive Mitchell's version....

I'm aware of this circuit but get the impression it doesn't blink.  I'd like
a blinking LED.  Thanks.

DS

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads


2002\10\20@074852 by Roman Black

flavicon
face
David & Ann Scott wrote:

> > You can buy off the shelf 300uH inductors. They are ready for use.
>
> I don't have any cores - unknown or known.  I would like to buy what I need
> but don't know where to start (seems they come in a wide array of shapes,
> sizes, types & materials).  I've used the RF chokes (J.W. Miller) from
> DigiKey but would like to know how to wind my own.  The RLC circuit for
> checking will be useful though.  Thanks Peter.


Try some pre-wound dumbell core chokes, Farnell
have some excellent ones i've been using lately,
8mm diam by 13mm high, good ferrite, low dc ohms,
good current, small size etc etc.

Listed in their catalogue page 597 as "Panasonic
high power series - ELC" and about $1 USD in singles.

My suggestion would be to buy a few sizes from
68uH up to 1000uH, with the 470uH being excellent
for most small SMPS up to 1 amp. They are also
well suited to wrapping another winding around
the existing winding.

For cores, you can use the figure-8 ferrite beads
(RF balun type) from any hobby shop, I got 100uH
from 40 turns so about 70 turns will give you 300uH
but they are a pain to wind, like toroids you have to
thread a lot of wire and with the figure-8 you
need to have each side reverse wound.

The dumbells are best, you can salvage them from
old TV's and just rewind to suit your needs and they
are MUCH easier to wind than formers you have to
thread.

If you need higher power inductors then try the
FERRITE toroids from Jaycar.com.au which are
superb in price and performance.

I also suggest buying a multimeter that measures
resistance and inductance, $45 should get you a
decent one. :o)
-Roman

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics


2002\10\20@082332 by Roman Black

flavicon
face
Roman Black wrote:

> I also suggest buying a multimeter that measures
> resistance and inductance, $45 should get you a
> decent one. :o)

Sorry, that should have said "measures CAPACITANCE
and inductance"...
-Roman

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics


2002\10\20@143412 by Peter L. Peres

picon face
On Sun, 20 Oct 2002, Roman Black wrote:

*>Roman Black wrote:
*>
*>> I also suggest buying a multimeter that measures
*>> resistance and inductance, $45 should get you a
*>> decent one. :o)
*>
*>Sorry, that should have said "measures CAPACITANCE
*>and inductance"...

Could you mention a few types you are familiar with ? (I'd really like a
manual RLC bridge but I don't have the room for it).

Peter

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics


2002\10\20@143414 by Peter L. Peres

picon face
On Sat, 19 Oct 2002, David & Ann Scott wrote:

*>> From: Peter L. Peres
*>> Determining inductance and turns for unknown cores is a problem without
*>> instruments. The aircoil will do it right but as you said, it is too
*>> large.
*>>
*>> You can buy off the shelf 300uH inductors. They are ready for use.
*>
*>I don't have any cores - unknown or known.  I would like to buy what I need
*>but don't know where to start (seems they come in a wide array of shapes,
*>sizes, types & materials).  I've used the RF chokes (J.W. Miller) from
*>DigiKey but would like to know how to wind my own.  The RLC circuit for
*>checking will be useful though.  Thanks Peter.

Watch out that RCL circuit will overstress most small off the shelf
inductors. It should only be used for larger SMPSU inductors (say from
0.5 cu. in. volume up).

If you want to buy a core aim for a core rated to work at between 20 and
100kHz (the usual frequency range for what you are trying to build - this
is what the material determines) and meant for dc/dc converter use (it
should have a Q above 20 in any case). The size is given by watts you wish
to put through it (in the mentioned frequency range), cores in catalogs
are listed by power among other things. For a LED you want something
around 0.5W (white 5V led at 40mA * 2 for circuit efficiency). It;s okay
to choose the next larger size.  I'd choose a pot core instead of a toroid
as toroids are hard to wind (and unwind). Once you choose a core like this
you will also know its Al which will allow you to determine the number of
turns required. Use the thickest wire that will fit the required number of
turns on your core (within reason - no need to wind busbars here)).

this is it, in a one paragraph form ;-)

Peter

PS: If the circuit you have in mind is the one I have in mind then you can
use a larger inductor without trouble imho - even 1mH should work.

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics


2002\10\21@100151 by Roman Black

flavicon
face
Peter L. Peres wrote:

> *>> I also suggest buying a multimeter that measures
> *>> resistance and inductance, $45 should get you a
> *>> decent one. :o)
> *>
> *>Sorry, that should have said "measures CAPACITANCE
> *>and inductance"...
>
> Could you mention a few types you are familiar with ? (I'd really like a
> manual RLC bridge but I don't have the room for it).


The one i'm using now is a Jaycar.com.au item,
an older model of their QM-1445 item, mine has
a 2mH inductance range, sad to see their new
model only has 20mH to 20H ranges, as the 2mH
range is the only one really good for small
inductors. The price is still cheap, $64 AUD
or $35 USD. But the new one has a temperature
probe -20'C to 800'C range which I suppose is
worth something, and this IS a full multimeter
with volts, amps etc, good for newbies.

A call around some of the Jaycar stores may reveal
old stocks of the model I got about 3 years back,
model QM-1480. I really think the 2mH range is
needed if you want to wind smaller inductors.

I also have a good RLC bridge my dad built as
part of his training and gave to me when I was a
pup, but unless you want to tune resonant circuits
I think they suck as a device to measure capacitance
or inductance, especially when you have hundreds
of parts to sort through.

The thing I DON'T like about my Jaycar inductance
meter is the zero offset is -15uH, and it takes
a couple of seconds to stabilise. But it will
read in digits to one uH when in the 2mH range.

There still has been no response from any inductor
gurus here about building a good analogue inductance
meter?

Surely all it needs is an oscillator using the
inductor under test, and an analogue meter showing
freq which is then calibrated in uH??
-Roman

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@140325 by Peter L. Peres

picon face
On Mon, 21 Oct 2002, Roman Black wrote:

*>A call around some of the Jaycar stores may reveal
*>old stocks of the model I got about 3 years back,
*>model QM-1480. I really think the 2mH range is
*>needed if you want to wind smaller inductors.

Ok, I will check. Although I have no idea what or who Jaycar is.

*>I also have a good RLC bridge my dad built as
*>part of his training and gave to me when I was a
*>pup, but unless you want to tune resonant circuits
*>I think they suck as a device to measure capacitance
*>or inductance, especially when you have hundreds
*>of parts to sort through.

I do not aggree. A bridge is THE instrument to measure L and C with.
Especially a bridge with variable generator frequency. I'll eventually
build one that will use an external signal generator as source. Bridges
are especially useful if you are trying to tune or match parts to a spec
because the indication (at least on a manual bridge) is relative to the
reference, so you read error wrt wanted spec directly.

Has any1 got a bridge schematic or link that uses synchronous quadrature
detectors to read Re and Im simultaneously ? Because this is what I want
to build.

*>There still has been no response from any inductor
*>gurus here about building a good analogue inductance
*>meter?
*>
*>Surely all it needs is an oscillator using the
*>inductor under test, and an analogue meter showing
*>freq which is then calibrated in uH??

The scale would be a square root one. Not nice for linearity. You could
calibrate it by slowly adding turns to a pot core ... lots of time. But
less than a weekend's work.

I've tried to make a L meter using W = L*i^2/2. At constant frequency one
switches a current into the coil (through a precise current limiter), then
cuts the current and rectifies and integrates the resulting flyback pulse,
to obtain some charge in a capacitor.  When discharged continuously
through a constant current source, this voltage should be proportional to
L, less nonlinear losses. But it is not quite, even if using ideal diodes
etc in SPICE. With real world components linearity is terrible.

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@140536 by Peter L. Peres

picon face
On Mon, 21 Oct 2002, Roman Black wrote:

*>There still has been no response from any inductor
*>gurus here about building a good analogue inductance
*>meter?

No, but:

http://www.google.com/search?hl=en&ie=ISO-8859-1&q=inductance+meter

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@143034 by Jim

flavicon
face
> There still has been no response from any inductor
> gurus here about building a good analogue inductance
> meter?

I don't 'buy' when I can buy the best (HP, etc) for only
pennies on the dollar (eBay and other sources like
hamfets) or use a network analyzer and get *exact*,
reliable results - often at the very frequency of
interest versus some other 'test' frequency that
simple meters use ...

Besides, these cheaper designs won't give you "Q"
which is an important parameter to me ...


How about this:

o .001 uHy (1 nHy) to 100 mHy (most units measure to 150 mHy)
o .010 pf to 1 uF (most units measure to 1.5 uF)
o AUTOMATIC RANGING
o 1% of reading typical -

- Typical means the average error of  83 different components compared to
an:

o HP4275A digital L/C meter (test frequency 1MHz) for
   components ranging from .1uHy to 1mHy and 2.7pf to .068uF,
o B&K 878 digital LCR meter (test frequency 1KHz) for
   components ranging from 1mHy to 100mHy and .1uF to 1.6uF.

http://www.aade.com/lcmeter.htm



>
> Surely all it needs is an oscillator using the
> inductor under test, and an analogue meter showing
> freq which is then calibrated in uH??

You have just described the Boonton 260A - except for the
additinal circuitry that allows measurement of the
"Q" of the tuned circuit!


RF Jim



> -Roman
>

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@144525 by Peter L. Peres

picon face
I asked for symchronous demodulator L meter and I got:

http://www.qsl.net/va3iul/L_meter/L_meter.htm

Be sure to visit the home page, lots of good articles.

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@151821 by Roman Black

flavicon
face
Peter L. Peres wrote:

> Ok, I will check. Although I have no idea what or who Jaycar is.

Thats why I said "jaycar.com.au" earlier in
the same post. :o)


>> *>I also have a good RLC bridge
>
> I do not aggree. A bridge is THE instrument to measure L and C with.

You're kidding right?? You think it's better
to have to turn a knob until you see it "peak"
then have to read the inductance based on the
knob position?? Better than just seeing the
inductance on a meter? Now I know you don't
have thousands of inductors in a tub like I do.


> *>Surely all it needs is an oscillator using the
> *>inductor under test, and an analogue meter showing
> *>freq which is then calibrated in uH??
>
> The scale would be a square root one.

Huh?? So if you have an oscillator where the
inductor is the timing component and you double
the inductance the freq does what?
-Roman

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@153226 by Jim

flavicon
face
 "Has any1 got a bridge schematic or link that
  uses synchronous quadrature detectors to read
  Re and Im simultaneously ?"

Hmmm .. you could be in for a difficult time on the
road ahead getting into measurements 'phase measurement'
... it requires exotic test equipment as the *now* ancient
HP 8405A Vector Voltmeter (an all solid-state instrument
introduced in the late 1960's and often found lurking on
eBay for a song) or something as equally insidious (and not
quite as rare but still found on eBay) known as a dual-trace
oscillograph embodied into what we commonly call 'a scope'
...

RF Jim

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@162630 by Peter L. Peres

picon face
On Tue, 22 Oct 2002, Roman Black wrote:

*>>> *>I also have a good RLC bridge
*>>
*>> I do not aggree. A bridge is THE instrument to measure L and C with.
*>
*>You're kidding right?? You think it's better
*>to have to turn a knob until you see it "peak"
*>then have to read the inductance based on the
*>knob position?? Better than just seeing the
*>inductance on a meter? Now I know you don't
*>have thousands of inductors in a tub like I do.

I do not have thousands of inductors but sometimes I make my own and then
I want to know a lot more than L about them. Jim Poll (rfjim) uses his
network analyzer to do what the bridge does by hand. The links I sent
before also lead to a L and Q meter that use the bridge method. Can you
see a pattern here ?

Also blindly trusting the readout of digital 'automatic' instruments can
lead to interesting results when the coil or capacitor is used at another
frequency. There was a AM radio circuit I saw that uses electrolytic
capacitors (good ones, couple of hundred uF, no tricks), as resonant
tuning circuits around 1 MHz. A bridge will spare you these surprises.

*>> *>Surely all it needs is an oscillator using the
*>> *>inductor under test, and an analogue meter showing
*>> *>freq which is then calibrated in uH??
*>>
*>> The scale would be a square root one.
*>
*>Huh?? So if you have an oscillator where the
*>inductor is the timing component and you double
*>the inductance the freq does what?

f1 = 1/sqrt(2) * f0

One of the links I posted (the man is in Australia), leads to a
peaking/dip type of L meter that uses a variable CAPACITOR to tune the
unknown coil to a FIXED frequency. This leads to linear scale if and only
if you use a 'ham' variable with linear delta-c. Since broadcast tuning
variables have a C^2 characteristic (so the frequency scale is linear),
they are not suitable for this. Ever wondered why the sections in a
broadcast variable have such a funny rounded shape, like a sea snail shell
? The link is here:

(homepage)
http://www4.tpgi.com.au/users/ldbutler/index.htm

The one you want is:

http://www4.tpgi.com.au/users/ldbutler/RFInducMeter.htm

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@163325 by Peter L. Peres

picon face
On Mon, 21 Oct 2002, Jim wrote:

*>  "Has any1 got a bridge schematic or link that
*>   uses synchronous quadrature detectors to read
*>   Re and Im simultaneously ?"
*>
*>Hmmm .. you could be in for a difficult time on the
*>road ahead getting into measurements 'phase measurement'
*>... it requires exotic test equipment as the *now* ancient
*>HP 8405A Vector Voltmeter (an all solid-state instrument
*>introduced in the late 1960's and often found lurking on
*>eBay for a song) or something as equally insidious (and not
*>quite as rare but still found on eBay) known as a dual-trace
*>oscillograph embodied into what we commonly call 'a scope'

I was thinking along the lines of a RLC bridge with two MC1496 analog
multipliers fed with 0 and 90 degrees carrier for synchronous detection
and separate readouts on two panel 3 1/2 digit DVMs using some opamps as
glue and a clever switch or two to allow the 90 degree carrier shifter to
be calibrated using the DVMs manually, for each frequency. I guess that
would be 3/4 of a vector voltmeter.

I cannot afford to keep a properly calibrated scope for phase measurements
on the screen at home, for occasional use (and two sets of probes, and
two of everything else).

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@170854 by Russell McMahon

face
flavicon
face
> There still has been no response from any inductor
> gurus here about building a good analogue inductance
> meter?
>
> Surely all it needs is an oscillator using the
> inductor under test, and an analogue meter showing
> freq which is then calibrated in uH??

This should be able to be done very well using a processor with A2D and a
little magic.

Project anyone ?



           RM

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@180439 by Jim

flavicon
face
Peter, I don't know *why* you need a phase-capable
indicating system for use with a bridge - when
a simple 'detection' (diode, meter, etc) will
suffice to detect 'the null' when the bridge
has reached the balanced state ... a simple
diode RF detector outfitted to your favorite
DVM can provide that function ...

Between what two points do you hope to view
the phase and what information might this reveal?

When I do check/memasurement of an series inductor/capacitor
combo across a 50 Ohm line with my network analyzer
I can observe for 1) reflection coefficient at
resonance (also verified by phase 'swing' as the
resonant point is tuned through) as well as observe
where the 3 dB points are in order to determine
circuit Q.

I could read inductor directly by looking at Refl. Coef.
and phase angle then using a Smith Chart (or equation)
compute the actual inductance value.

As to needing 'extra pairs of scope probes' for
a scope for to be used in a particular dedicated
application - I would suggest the use of 'resistive
dividers' in the manner of 'minimum-loss matching
pads' (or even the use of buffer amplifiers!)
designed placed at the output of the DUT (or test
set) and 50 (or 75 or 93) Ohm cable routed for display
on  the O-scope where said cable is terminated in
it's characteristic Z. Many newer/high frequency
scopes also have a termination selection built-in.

The point being, the lowly O-scope should not be
overlooked for some of the more slightly exotic
applications such as observing phase and magnitude
of two signals ...

RF Jim

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@183012 by Peter L. Peres

picon face
On Tue, 22 Oct 2002, Russell McMahon wrote:

*>> There still has been no response from any inductor
*>> gurus here about building a good analogue inductance
*>> meter?
*>>
*>> Surely all it needs is an oscillator using the
*>> inductor under test, and an analogue meter showing
*>> freq which is then calibrated in uH??
*>
*>This should be able to be done very well using a processor with A2D and a
*>little magic.

PICs can measure frequency directly, much more accurately than any A/D
availlable today.

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@184313 by Peter L. Peres

picon face
On Mon, 21 Oct 2002, Jim wrote:

*>Peter, I don't know *why* you need a phase-capable
*>indicating system for use with a bridge - when
*>a simple 'detection' (diode, meter, etc) will
*>suffice to detect 'the null' when the bridge
*>has reached the balanced state ... a simple
*>diode RF detector outfitted to your favorite
*>DVM can provide that function ...

*>Between what two points do you hope to view
*>the phase and what information might this reveal?

I want to be able to use it to measure/balance complex RLC loads like
transformer + cable + transformer or telephone line equivalent or resonant
transducers and other such things. Otherwise I would not bother.

*>As to needing 'extra pairs of scope probes' for
*>a scope for to be used in a particular dedicated
*>application - I would suggest the use of 'resistive
*>dividers' in the manner of 'minimum-loss matching
*>pads' (or even the use of buffer amplifiers!)
*>designed placed at the output of the DUT (or test
*>set) and 50 (or 75 or 93) Ohm cable routed for display
*>on  the O-scope where said cable is terminated in
*>it's characteristic Z. Many newer/high frequency
*>scopes also have a termination selection built-in.

Yes except @home I use an old 2 x 25MHz scope. Buffer amplifiers could be
used, good idea. Now all I have to do is match them in phase and
compensate for any distortion they may induce (when is an ellipsis an
ellipsis, and where are its apexes ? ;-).

*>The point being, the lowly O-scope should not be
*>overlooked for some of the more slightly exotic
*>applications such as observing phase and magnitude
*>of two signals ...

That is correct but squinting at a trace and using a ruler or protractor
or something like that on a 5 inch screen with more than enough parallax
is less elegant and less accurate than reading a pair of DVMs. The DVM
'vector voltmeter' would also be portable more or less.

I think I tried to use my home scope only once in XY mode and I got a
'snake' curve from connecting both channels to a sine wave source. Needs
linearity calibration (I doubt it has such a control) or junking ;-).
Remember on cheap scopes the X and Y amplifiers are built very different.

Peter

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@210545 by Russell McMahon

face
flavicon
face
> *>> There still has been no response from any inductor
> *>> gurus here about building a good analogue inductance
> *>> meter?
> *>>
> *>> Surely all it needs is an oscillator using the
> *>> inductor under test, and an analogue meter showing
> *>> freq which is then calibrated in uH??
> *>
> *>This should be able to be done very well using a processor with A2D and
a
> *>little magic.
>
> PICs can measure frequency directly, much more accurately than any A/D
> availlable today.

Agreed.
I didn't make myself clear - what I meant was that that inductance should be
able to be measured by a processor based method, not that you would
necessarily directly translate the analog method.

eg something using V= L di/dt with a comparator detecting when current
reaches a certain level. Inductance is then inversely proportional to time
to trip point. Probably doable with not too much more than the processor.
(And probably exists as a practical circuit on a dozen websites already?)

       RM

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@230147 by dwheeler

flavicon
face
my.integritynet.com.au/purdic/lc-meter-project.htm

----- Original Message -----
From: "Russell McMahon" <.....apptechKILLspamspam@spam@PARADISE.NET.NZ>

> to trip point. Probably doable with not too much more than the processor.
> (And probably exists as a practical circuit on a dozen websites already?)

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\21@233839 by Jim

flavicon
face
> I want to be able to use it to measure/balance complex RLC loads like
> transformer + cable + transformer or telephone line equivalent or
> resonant transducers and other such things. Otherwise I would
> not bother.


I have dome this uisng the common dual-trace scope and a simple
resistive 'bridge' (of my own design) and compared the results
with an authentic General Radio bridge (at AM radio Broadcast
frequencies). I think I went on, at little length, awhile back
on using this deceivingly *simple* technique to measure *complex*
impedances (this play on words _was_ intentional!).

The objective was to find the complex Z (Impedance, in series
form: R + jX) and it was easily accomplished.

ALSO the benefit of this technique is the EASY means by which
resonance (or inducative/capacitive lead/lead effects) can be
seen/found (by watching phase changes BETWEEN the two channels)
while wildly tuning a network - as is sometimes done when
desparate to observe what various 'wild' speculative changes
are made!

>
> I think I tried to use my home scope only once in XY mode and I got a
> 'snake' curve from connecting both channels to a sine wave source. Needs
> linearity calibration (I doubt it has such a control) or junking ;-).
> Remember on cheap scopes the X and Y amplifiers are built
> very different.

I think this is where some people make the mistake - even the
old Tek scopes (453, 454, 465) didn't have matching X and Y
amps/channels (especially into the HF region) - the secret
THEN is to use the scope in dual-trace mode (I have mentioned
this before - no?) and compare phase  differences ... by proper
adjustment of variable sweep-time and on the CRT it is a SIMPLE
matter to observe zero-crossing and determine phase easily - the amplitude,
then, does not come into play (ONLY zero-crossing
RELATIONSHIP between the two sinusoids) ...


Ignore those textbooks and profs who recommend 'Lissajou'
patterns - they are a nice laboratory curiosity and
were of more value years ago when dual-trace scopes
did not exist ... I have used this dual-trace technique
with a realy crudely fabricated 'bridge' and obseved
results up through 50 MHz - cables were terminated AT
the scope using homebrew 50 Ohm in-line terminations
fabricated using BNC male connector into which was
soldered a VERY small 50 Ohm R and a BNC female jack.

Not all of us have had access to sophisticated test
gear (or even the the old manual test gear!) forever
in our home laboratories - or even at some companies
we have worked at so we have had to 'make do' with
common lab gear and arriving at surprising results
at times!

RF Jim

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2002\10\22@032745 by Michael Rigby-Jones

flavicon
face
> Huh?? So if you have an oscillator where the
> inductor is the timing component and you double
> the inductance the freq does what?
> -Roman
>
Reduces by a factor of the square root of 2. e.g. Fnew =  Fold / 2^0.5

Regards

Mike

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listservspamKILLspammitvma.mit.edu with SET PICList DIGEST in the body


2002\10\22@041553 by Russell McMahon

face
flavicon
face
> > Huh?? So if you have an oscillator where the
> > inductor is the timing component and you double
> > the inductance the freq does what?
> > -Roman

> Reduces by a factor of the square root of 2. e.g. Fnew =  Fold / 2^0.5

You may have to specify HOW the inductor is being used to answer that
properly.
For an LC oscillator f 1/(2.Pi.sqrt(LC))
For an LR oscillator f = R/L
While an "LR" oscillator is a less normal concept it's entirely doable,
especially  with a little help  from electronics.

       RM

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email .....listservKILLspamspam.....mitvma.mit.edu with SET PICList DIGEST in the body


2002\10\22@054355 by Roman Black

flavicon
face
Russell McMahon wrote:
>
> > > Huh?? So if you have an oscillator where the
> > > inductor is the timing component and you double
> > > the inductance the freq does what?
> > > -Roman
>
> > Reduces by a factor of the square root of 2. e.g. Fnew =  Fold / 2^0.5
>
> You may have to specify HOW the inductor is being used to answer that
> properly.
> For an LC oscillator f 1/(2.Pi.sqrt(LC))
> For an LR oscillator f = R/L
> While an "LR" oscillator is a less normal concept it's entirely doable,
> especially  with a little help  from electronics.


Thanks Russell, that is why I specified an
"inductor" as the timing component, not an
"inductor AND capacitor" which is how I think
they read it.

When testing some 2 transistor SMPS boost
configurations I tried one that turned off when
the inductor reached a set current, performance
seemed very close to f=1/L. Didn't think I was
going crazy. ;o)
-Roman

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email EraseMElistservspam_OUTspamTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body


2002\10\22@062606 by Michael Rigby-Jones

flavicon
face
{Quote hidden}

I imagined that for an accurate maeasurement system you would require as
high a Q as possible, so I ASSumed an LC oscillator :o)

Regards

Mike

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email KILLspamlistservKILLspamspammitvma.mit.edu with SET PICList DIGEST in the body


2002\10\23@121508 by Peter L. Peres

picon face
On Mon, 21 Oct 2002, Jim wrote:

*>Not all of us have had access to sophisticated test
*>gear (or even the the old manual test gear!) forever
*>in our home laboratories - or even at some companies
*>we have worked at so we have had to 'make do' with
*>common lab gear and arriving at surprising results
*>at times!

I aggree. I will try to use a 2 channel scope as you said. We'll see.

thanks,

Peter

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestTakeThisOuTspammitvma.mit.edu


2002\10\23@141216 by Peter L. Peres

picon face
On Tue, 22 Oct 2002, Roman Black wrote:

*>When testing some 2 transistor SMPS boost
*>configurations I tried one that turned off when
*>the inductor reached a set current, performance
*>seemed very close to f=1/L. Didn't think I was
*>going crazy. ;o)

hehe. When Rcoil ~= 1ohm you do indeed have f = 1/L

Peter

--
http://www.piclist.com hint: To leave the PICList
spamBeGonepiclist-unsubscribe-requestspamBeGonespammitvma.mit.edu


More... (looser matching)
- Last day of these posts
- In 2002 , 2003 only
- Today
- New search...