On Friday, April 28, 2023 at 4:13:52 AM UTC-4, Jeff Liebermann wrote:
> >
> You might think that a soldering station, with a digital temperature
> display, is run by DC. Nope, they're powered by a PWM (pulse width
> modulated) waveform. There's some question as to whether this type is
> AC or DC. My vote is that PWM is AC.

Wait!!! You mean PWM Isn't only used to test cables!?!?!? Say it ain't so!!!!!!! Next thing you'll be saying is that there isn't any such thing as campagnolo special non-stretch shifting cables!

> If the soldering station
> regulator was an analog DC regulator, it could easily dissipate as
> much heat as the soldering station hand piece, which is not a good
> idea. Therefore, PWM is used to limit power dissipation.
> >This means that the only current from the iron to ground is
> >though the insulation of the transformer.
> Wrong. The tip is grounded on a modern iron. You can check for
> yourself with an ohmmeter. A ground tip is required to ESD
> (electrostatic discharge) specifications (ANSI/ESD S20.20-2007):

I remember being told long ago that one reason old ac inductive irons shouldn't be used in solid-state electronics is because the AC could be present at the tip and damage the parts. Have you ever heard that? An old electronics technician's wives tale perhaps?

> "Can a soldering station guarantee tip grounding?"
> <https://kb.hakkousa.com/Knowledgebase/10621/Can-a-soldering-station-guarantee-tip-grounding>
> >And is all low voltage and low current.
> It's not that simple and that's not the way ESD protection is
> specified:
> "Protection of Electrical and Electronic Parts, Assemblies and
> Equipment"
> <https://www.bystat.com/pdf/S2020-2007.pdf>
> The important spec is the energy delivered by the tip to the protected
> circuit. The waveform, capacitance and lead inductance need to be
> considered as well as tip voltage and ground resistance (not current).
> >Plus it was cart-before-the-horse since the standard was set
> >simply by measuring the leakage current on the half dozen companies
> >that manufactured units.
> A truly amazing fact. Yes, I'm sure the standards committee measured
> the existing products at some point. However, they're main interest
> was probably in what manner of specifications were required to make
> the device ESD safe and how was this to be measured.
>
> Once again, you get a score of zero, where nothing you wrote is true,
> correct or accurate.
> --
> Jeff Liebermann je...@cruzio.com
> PO Box 272 http://www.LearnByDestroying.com
> Ben Lomond CA 95005-0272
> Skype: JeffLiebermann AE6KS 831-336-2558

On 4/28/2023 1:54 AM, Jeff Liebermann wrote:
> On Thu, 27 Apr 2023 11:37:41 -0500, AMuzi <am@yellowjersey.org> wrote:
>
>> Guilty as charged on yet another typo.
>> I didn't understand what was humorous about that excerpt.
>
> Sorry. It was the best I could do with a typo error. Since I knew my
> comment might be offensive, I added the part about RightWingGPT as a
> distraction and peace offering. Obviously, it didn't work. Please
> accept my humble apology and I promise not to do it again.
>

No offense taken. One of RBT's virtues is broad subject
matter and viewpoint diversity.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

On Fri, 28 Apr 2023 03:00:48 -0700 (PDT), "funkma...@hotmail.com"
<funkmasterxx@hotmail.com> wrote:

>On Friday, April 28, 2023 at 3:28:53?AM UTC-4, Jeff Liebermann wrote:
>> On Thu, 27 Apr 2023 21:43:02 -0700 (PDT), "funkma...@hotmail.com"
>> <funkma...@hotmail.com> wrote:
>>
>> >Not to mention for the past 20 years or so high-frequency technology is more standard for most electronics mfg facilities. We use these
>> >https://store.metcal.com/en-us/shop/soldering-desoldering/soldering-desoldering-systems/mx-series/MX-500AV
>> >But they've been around since the early 2000s. I have an old one that I retrieved from the trash at work many years ago and repaired.
>> I didn't know such things existed. Up to 70 watts of 13.56 MHz RF
>> should do nicely for jamming low frequency RFID/NFC tag readers:

>That 70 watts is the overall consumption of the product, not the RF power generated at the tip.

Look at the data sheet:
<https://store.metcal.com/en-us/shop/soldering-desoldering/soldering-desoldering-systems/mx-series/MX-500AV>
"Output Power: Variable, 40 W max.*"
However, I did pick the wrong number (at 1am).
This video proclaims 45 watts:
<https://www.youtube.com/watch?v=FS2NqyVDoqk>

>These things are approved by FCC, ISED, and CE EMC compliance requirements. 70 watts of unintentional RF wouldn't pass unintentional radiator requirements. They're obviously suppression the radiation such that it doesn't register on the spectrum analyzer.

This repair video shows the guts and case. Not much of a repair
because the MX-500AV fixed itself:
<https://www.youtube.com/watch?v=FAipMcwfuqI>
I would say it's very well shielded. This is the first time I've paid
any attention to such soldering irons. Offhand, I would guess(tm)
that it's an induction heater. At 3.58 MHz, the small antenna is
horribly inefficient. Any testing would be within the near field
radius, where the signal decreases with the inverse cube of the
distance instead of inverse square. Ok, I'll stop worrying about RF
leakage.

>> <https://store.metcal.com/en-us/shop/soldering-desoldering/soldering-desoldering-systems/mx-series/>
>> <https://www.youtube.com/@MetcalOKI/videos>
>>
>> "Reverse engineering a high-end soldering station"
>> <https://habr.com/en/articles/451246/>
>
>This is a curious line from that link: "the resulting power starts dissipating on the active resistance of the inductor coil, which, due to the skin effect, is much higher than an ordinary multimeter can register."
>That's very curiously worded, and if taken _as_ it's written isn't quite right.

My guess(tm) is that it's a small induction heater. All that's needed
is a high loss ferrite rod and a tinned iron tip. The DC resistance
of the core will vary from very low (powdered iron) to fairly high
(iron oxide). I'll need to read the patent descriptions before I make
any more bad guesses.

>"the resulting power starts dissipating on the active resistance
>of the inductor coil, which is much higher than an ordinary
>multimeter can register."

What is "active resistance"? I guess he's confusing DC resistance
with skin effect, where RF conduction occurs near the surface. One
cannot measure RF conductivity with a DC ohmmeter.

>would be true, because most DVMs use DC to make resistance
>measurements and and an inductors impedance only really become
>obvious in the presence of AC. However I would have used
>'reactance' in place of 'reactive resistance' (more appropriately
>'inductive reactance'), or at the very least 'impedance'....so
>"[inductive reactance] due to skin effect is much higher than
>an ordinary multimeter can register." would be true.

Agreed. If they coated a solenoid wound coil in an induction heater
with lossy ferrite material, which heats by hysterisis loss, the coil
would get quite hot. No need for a rod down the center of the coil.
However, the various photos seem to show a long rod, which I assume
conducts the heat to the tip, so I think they used a rod, not a coated
coil. Again, this is a guess(tm).

>""the resulting power starts dissipating on the active resistance
>of the inductor coil due to the skin effect."

Again, what is "active resistance"? I've never heard of the term. RF
impedance seems like a more likely term.

>would also have been true, since skin effect becomes the dominant
>form of conduction in inductors at higher frequencies, hence wave
>guides (as an RF guy you were aware of that).

Agreed. If I knew the permeability and resistivity of the rod or
coating, I could calculate the skin depth.

>I think however that
>the sentence as worded gives the implication that an "ordinary multimeter"
>can't read high resistance due to skin effect. Maybe it's just me.....

Almost correct. An ordinary ohmmeter will read DC resistance
(resistivity) and nothing else. For RF frequencies, skin effect needs
to be considered. A low frequencies, I like to use an RF ammeter:
<https://www.google.com/search?q=rf+ammeter&tbm=isch>
For resistance, it's just the RF voltage across the transmission line,
divided by RF current. Except at very low RF frequencies, the RF
resistance will be very different from the DC resistance.

>This is actually a very nice video giving a fundamental description
>of the whole system: https://www.youtube.com/watch?v=S9Wmqc9O24w

Thanks. Looks like I was close. I'm too lazy to go back fix my
guesses. It's definitely an induction heater. However, my ferrite
rod should have been a copper rod coated with ferrite material. I
didn't mention the Curie effect temperature control, but it's similar
to the system used in ancient old Weller soldering stations.

"Self-regulating heater utilizing ferrite-type body"
<https://patents.google.com/patent/US5182427>

>It actually reminds me of the "technology" used on old-school fluid
>level detection sensors using NTC thermistors. The application is
>to drive the thermistor with a constant current such that the power
>dissipated as heat affects the resistance of the device. It the
>voltage across the device is monitored, when it drops below a
>certain level a comparator circuit can be used to switch the
>current down (lower or off) which results in a oscillation.
>As long as the device is held in free air within a certain ambient
>range, this 'self heating' will keep the oscillation alive. However
>when the device is immersed in a liquid, the increased thermal density
>(conductivity, K) of the liguid allows the conduction of the heat
>away from the device to the point that the temperature of the device
>stabilizes and the oscillation stops, or at least does cross the
>comparator reference. When the oscillation stops, you know the
>sensor has detected a liquid or the sensor has failed (a great
>version of a self-diagnostic).
>
>There are obvious drawback to this, one being that it doesn't work
>very well in extreme cold or hot air temperatures, the other being
>that thermistors are inherently fragile (those transients over time
>don't help).

I've never heard of this device. I thought this might be the patent,
but maybe not since there's no mention of oscillation. It does what
you describe, but with DC:
"Thermistor liquid level sensor and method for making same"
<https://patents.google.com/patent/US3479875A/en>

--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On Fri, 28 Apr 2023 03:07:04 -0700 (PDT), "funkma...@hotmail.com"
<funkmasterxx@hotmail.com> wrote:

>On Friday, April 28, 2023 at 4:13:52?AM UTC-4, Jeff Liebermann wrote:
>> If the soldering station
>> regulator was an analog DC regulator, it could easily dissipate as
>> much heat as the soldering station hand piece, which is not a good
>> idea. Therefore, PWM is used to limit power dissipation.
>> >This means that the only current from the iron to ground is
>> >though the insulation of the transformer.
>> Wrong. The tip is grounded on a modern iron. You can check for
>> yourself with an ohmmeter. A ground tip is required to ESD
>> (electrostatic discharge) specifications (ANSI/ESD S20.20-2007):

>I remember being told long ago that one reason old ac inductive
>irons shouldn't be used in solid-state electronics is because
>the AC could be present at the tip and damage the parts. Have
>you ever heard that? An old electronics technician's wives tale
>perhaps?

If you change two words in your question, it would be correct. Change
"old AC inductive irons" to "old AC inductive soldering guns".
<https://www.google.com/search?q=weller+soldering+gun&tbm=isch>

In the distant past, I've successfully destroyed components with a
soldering gun. I haven't owned or used one since about 1965. The
classic Weller soldering gun is a poorly shielded step down
transformer, that heats a copper wire tip at some fairly high current.
The resulting magnetic field is proportional to the current. More
current, more magnetic field, and more damage to electronic
components. You can use a soldering gun as a degausser:
<https://99mpg.com/mikestips/solderingiorndegau/>

I couldn't find the tip current online. If it can make a copper wire
tip glow almost red, it's a rather large current. Any wire that comes
close to the iron will see some induced AC current (with a big jolt on
cold start). Not recommended near sensitive electronics.

Soldering irons don't have such high currents or fields.

I have the test equipment needed to measure the tip current and field,
but don't own a soldering gun. Sorry.

--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

On 4/28/2023 4:05 PM, Jeff Liebermann wrote:
> You can use a soldering gun as a degausser:
> <https://99mpg.com/mikestips/solderingiorndegau/>

Nice.

--
- Frank Krygowski

On Friday, April 28, 2023 at 3:41:46 PM UTC-4, Jeff Liebermann wrote:
> On Fri, 28 Apr 2023 03:00:48 -0700 (PDT), "funkma...@hotmail.com"
>
> Ok, I'll stop worrying about RF
> leakage.

Especially since it's an issue that's already been solved

> What is "active resistance"? I guess he's confusing DC resistance
> with skin effect, where RF conduction occurs near the surface. One
> cannot measure RF conductivity with a DC ohmmeter.

As I noted in my response, He should have used 'reactance' (the inductive impedance portion of the impedance vector)

> >I think however that
> >the sentence as worded gives the implication that an "ordinary multimeter"
> >can't read high resistance due to skin effect. Maybe it's just me.....
> Almost correct. An ordinary ohmmeter will read DC resistance
> (resistivity) and nothing else. For RF frequencies, skin effect needs
> to be considered. A low frequencies, I like to use an RF ammeter:
> <https://www.google.com/search?q=rf+ammeter&tbm=isch>
> For resistance, it's just the RF voltage across the transmission line,
> divided by RF current. Except at very low RF frequencies, the RF
> resistance will be very different from the DC resistance.

I actually spent a good 20 years of my career working on RF and very high data rate systems. I'm very familiar with RF "black magic".

> "Self-regulating heater utilizing ferrite-type body"
> <https://patents.google.com/patent/US5182427>
> >It actually reminds me of the "technology" used on old-school fluid
> >level detection sensors using NTC thermistors.
<snipped for brevity>
>
> I've never heard of this device. I thought this might be the patent,
> but maybe not since there's no mention of oscillation. It does what
> you describe, but with DC:
> "Thermistor liquid level sensor and method for making same"
> <https://patents.google.com/patent/US3479875A/en>

That's close. However, I should mention the result of the application resembles a squareware, but technically is more appropriately considered to be "changing DC". The signal applied to the sensor is a constant current source.. We're switching between a 'high' and 'low' current source as the voltage drifts above and below the comparator reference. As the impedance of the sensor changes the resultant voltage is measured which is a square(ish) wave. We aren't really generating AC as much as we are simply monitoring the changing DC.

Interesting tangent - The DC level is integral to the diagnostics presented to the user.
1) the fact the we're monitoring the changing state tells us that the sensor is dry and in good working condition. It isn't likely that any failure could result in the squarewave output within the voltage and period requirements.
2) if the monitored voltage is at the maximum value (as measured during the power-on diagnostics) or at ground, that's an indication to the user that the sensor is open (or not connected) or shorted to ground. This information is presented in the UI.
3) Voltage values which are at some level below the open circuit voltage or above short circuit voltage but fail to cross the comparator reference threshold are reported as "wet". If the operator knows that the sensor is in fact dry, it's an indication of another system fault.