elektroda.net NewsGroups Forum Index - Electronics Design - Induction heating / cooking - and where to get low ESR high
Ian Stirling
Guest
Guest
Thu Mar 04, 2010 12:39 pm
I was wondering how these things worked - after seeing some
on ebay.
http://www.st.com/stonline/products/literature/an/12443.pdf
turned up after a bit of searching - a design for one.
Basically they end up for a 2.5Kw device as a 30-50KHz tank
circuit comprising the coil and a big cap, with a Q of around
10.
So, 25KW of circulating power.
That said - it doesn't actually look that hard.
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
For obvious reasons - I'm looking for ~50A ideally per cap.
The caps I have found - vishay's phao series - would
in principle work - and I'd only need one even. But given that
they are 4*3*6", and have porcelain standoffs, I feel they
are unlikely to be cheap.
:)
The ones in the ST design are ~2*1.5*1.5" - not small - but
much more managable.
But the ones in the chinese cookers are _MUCH_ smaller yet.
Are these only available in china?
Tim Williams
Guest
Guest
Fri Mar 05, 2010 3:01 pm
"Ian Stirling" <usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
Quote:
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
Quote:
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
rated current before, they don't break a sweat. You could easily suck 3-4A
through these things.
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
Quote:
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings.
Also, they've been known
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Ian Stirling
Guest
Guest
Thu Mar 11, 2010 6:46 pm
Tim Williams <tmoranwms_at_charter.net> wrote:
Quote:
"Ian Stirling" <usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
Interesting.
Quote:
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
naah - not really a problem - at least for playing around with.
Quote:
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings. Also, they've been known
Or they get ratings that are actually real - not produced by someone
The Chinese don't need no steenkin' ratings.
Also, they've been known
Or they get ratings that are actually real - not produced by someone
looking at a cap and thinking 'let's spec it to 100mA'.
Quote:
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Been playing with my new induction device today, violating its specs.
:)
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Which is handy.
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
On a more DIY note - do you have any sources for the ferrite bars used to reduce the field under the pan?
Tim Williams
Guest
Guest
Thu Mar 11, 2010 7:01 pm
"Ian Stirling" <usenet_at_mauve.plus.com> wrote in message
news:avadnQgF6p7tsQTWnZ2dnUVZ7tmdnZ2d_at_brightview.co.uk...
Quote:
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Is the heavy stuff All-Clad? They sandwich copper into that stuff.
Except for the sides, which is really terrible for the omlette pan we have:
the sides are raw stainless, so they get black hot before the rest of the
pan is even sizzling.
Not to mention the general PITA that is a stainless surface -- *everything*
sticks to it. I wish they could make a cast iron clad frying pan!
Regular steel or iron (or even aluminum) pan should work okay though.
Speaking of aluminum, give it a try -- pick it up and wave it around, you
should be able to feel a repulsive "bubble" over the coil due to eddy
currents!
Quote:
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
boiling, then turn it down)
Piezo sensor or something? Neet!
Quote:
On a more DIY note - do you have any sources for the ferrite bars used to
reduce the field under the pan?
reduce the field under the pan?
Nope. You can find ferrite tiles and EMI slabs at various places, for $$$.
I've wondered if some of those EMI shielding products are useful (like the
flexible mats that claim mu_r ~ 10), but it would probably saturate too
easily, plus it would take a lot with the low permeability. And it's even
more expensive than sawing your own tiles, oh well.
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Dirk Bruere at NeoPax
Guest
Guest
Thu Mar 11, 2010 8:02 pm
On 11/03/2010 17:46, Ian Stirling wrote:
Quote:
Tim Williams<tmoranwms_at_charter.net> wrote:
"Ian Stirling"<usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
Interesting.
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
naah - not really a problem - at least for playing around with.
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings. Also, they've been known
Or they get ratings that are actually real - not produced by someone
looking at a cap and thinking 'let's spec it to 100mA'.
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Been playing with my new induction device today, violating its specs.
:)
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Which is handy.
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
On a more DIY note - do you have any sources for the ferrite bars used to reduce the field under the pan?
"Ian Stirling"<usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
Interesting.
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
naah - not really a problem - at least for playing around with.
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings.
Also, they've been known
Or they get ratings that are actually real - not produced by someone
looking at a cap and thinking 'let's spec it to 100mA'.
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Been playing with my new induction device today, violating its specs.
:)
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Which is handy.
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
On a more DIY note - do you have any sources for the ferrite bars used to reduce the field under the pan?
So, if you stick your head close do your metal fillings explode?
--
Dirk
http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show
Michael A. Terrell
Guest
Guest
Thu Mar 11, 2010 8:19 pm
Dirk Bruere at NeoPax wrote:
Quote:
On 11/03/2010 17:46, Ian Stirling wrote:
Tim Williams<tmoranwms_at_charter.net> wrote:
"Ian Stirling"<usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
Interesting.
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
naah - not really a problem - at least for playing around with.
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings.
Also, they've been known
Or they get ratings that are actually real - not produced by someone
looking at a cap and thinking 'let's spec it to 100mA'.
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Been playing with my new induction device today, violating its specs.
:)
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Which is handy.
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
On a more DIY note - do you have any sources for the ferrite bars used to reduce the field under the pan?
So, if you stick your head close do your metal fillings explode?
A modern version of the old 'Hot Foot'? ;-)
--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'
Ian Stirling
Guest
Guest
Thu Mar 11, 2010 8:58 pm
Tim Williams <tmoranwms_at_charter.net> wrote:
Quote:
"Ian Stirling" <usenet_at_mauve.plus.com> wrote in message
news:avadnQgF6p7tsQTWnZ2dnUVZ7tmdnZ2d_at_brightview.co.uk...
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Is the heavy stuff All-Clad? They sandwich copper into that stuff.
news:avadnQgF6p7tsQTWnZ2dnUVZ7tmdnZ2d_at_brightview.co.uk...
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Is the heavy stuff All-Clad? They sandwich copper into that stuff.
hahah.
Very not.
It's not-quite-bottom-of-the range pans.
Quote:
Except for the sides, which is really terrible for the omlette pan we have:
the sides are raw stainless, so they get black hot before the rest of the
pan is even sizzling.
the sides are raw stainless, so they get black hot before the rest of the
pan is even sizzling.
I found fringing a problem with subdiameter pans, which is a pity.
I'm unsure what the effect of a copper shorting ring round the top
of the pot would be. I can argue that it would be effective to kill
the fringing field, as well as it would kill the cooker.
Quote:
Not to mention the general PITA that is a stainless surface -- *everything*
sticks to it. I wish they could make a cast iron clad frying pan!
sticks to it. I wish they could make a cast iron clad frying pan!
You get them. Well - not cast iron - but iron.
I tend not to burn much on. And if I do - it comes off in moments with
a stainless pan, as I can be _LOTS_ more aggressive than I could with
a non-stick pan.
Quote:
Regular steel or iron (or even aluminum) pan should work okay though.
Speaking of aluminum, give it a try -- pick it up and wave it around, you
should be able to feel a repulsive "bubble" over the coil due to eddy
currents!
Speaking of aluminum, give it a try -- pick it up and wave it around, you
should be able to feel a repulsive "bubble" over the coil due to eddy
currents!
Nope - nothing.
The hob - according to various app-notes - is pulsed for a few ms - and
if it sees a load in range - it turns on.
Copper or Al, or indeed thick nonmagnetic stainless causes too much
current to flow, even at the lowest operating frequency, and it won't
turn on. (though why there isn't some magic distance at which it works,
I'm unsure. At full power, with a large pan, raising the gap between the
pan and hob changes it from ~2000W to ~1000W (before it turns off).
(magnetic stainless has a thinner skin effect)
Cheap steel non-stick works well.
Quote:
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
Piezo sensor or something? Neet!
boiling, then turn it down)
Piezo sensor or something? Neet!
Possibly, I was actually thinking more like a conventional mic.
The banging around when it boils is quite obvious, though the fan
noise may be annoying.
Quote:
On a more DIY note - do you have any sources for the ferrite bars used to
reduce the field under the pan?
Nope. You can find ferrite tiles and EMI slabs at various places, for $$$.
I've wondered if some of those EMI shielding products are useful (like the
flexible mats that claim mu_r ~ 10), but it would probably saturate too
easily, plus it would take a lot with the low permeability. And it's even
more expensive than sawing your own tiles, oh well.
reduce the field under the pan?
Nope. You can find ferrite tiles and EMI slabs at various places, for $$$.
I've wondered if some of those EMI shielding products are useful (like the
flexible mats that claim mu_r ~ 10), but it would probably saturate too
easily, plus it would take a lot with the low permeability. And it's even
more expensive than sawing your own tiles, oh well.
Possibly cheaper to rip apart a cheap induction cooker :/
I wonder if laminated 'pacman' shapes of foil and insulator would work to
shield the E field without getting too much losses in it. I suspect not.
I need to hook up a scope near it to see what the frequency is.
Dirk Bruere at NeoPax
Guest
Guest
Thu Mar 11, 2010 9:35 pm
On 11/03/2010 19:19, Michael A. Terrell wrote:
Quote:
Dirk Bruere at NeoPax wrote:
On 11/03/2010 17:46, Ian Stirling wrote:
Tim Williams<tmoranwms_at_charter.net> wrote:
"Ian Stirling"<usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
Interesting.
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
naah - not really a problem - at least for playing around with.
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings.
Also, they've been known
Or they get ratings that are actually real - not produced by someone
looking at a cap and thinking 'let's spec it to 100mA'.
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Been playing with my new induction device today, violating its specs.
:)
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Which is handy.
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
On a more DIY note - do you have any sources for the ferrite bars used to reduce the field under the pan?
So, if you stick your head close do your metal fillings explode?
A modern version of the old 'Hot Foot'?
And wedding rings, metal watch straps etc
--
Dirk
http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show
Michael A. Terrell
Guest
Guest
Thu Mar 11, 2010 9:42 pm
Dirk Bruere at NeoPax wrote:
Quote:
On 11/03/2010 19:19, Michael A. Terrell wrote:
Dirk Bruere at NeoPax wrote:
On 11/03/2010 17:46, Ian Stirling wrote:
Tim Williams<tmoranwms_at_charter.net> wrote:
"Ian Stirling"<usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
Interesting.
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
naah - not really a problem - at least for playing around with.
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings.
Also, they've been known
Or they get ratings that are actually real - not produced by someone
looking at a cap and thinking 'let's spec it to 100mA'.
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Been playing with my new induction device today, violating its specs.
:)
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Which is handy.
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
On a more DIY note - do you have any sources for the ferrite bars used to reduce the field under the pan?
So, if you stick your head close do your metal fillings explode?
A modern version of the old 'Hot Foot'? ;-)
And wedding rings, metal watch straps etc
How resonant would a wedding ring or watch band be at 60 KHz? The
wavelength is 5,000 meters. A quater wave antenna would be 1,250
meters.
--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'
Tim Williams
Guest
Guest
Fri Mar 12, 2010 12:32 am
"Michael A. Terrell" <mike.terrell_at_earthlink.net> wrote in message
news:4B9955CE.775CEF98_at_earthlink.net...
Quote:
And wedding rings, metal watch straps etc
How resonant would a wedding ring or watch band be at 60 KHz? The
wavelength is 5,000 meters. A quater wave antenna would be 1,250
meters.
How resonant would a wedding ring or watch band be at 60 KHz? The
wavelength is 5,000 meters. A quater wave antenna would be 1,250
meters.
What does "resonance" of a symmetric loop (it's not a loop antenna) have to
do with induction?
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Jamie
Guest
Guest
Fri Mar 12, 2010 12:35 am
Ian Stirling wrote:
Quote:
Tim Williams <tmoranwms_at_charter.net> wrote:
"Ian Stirling" <usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
Interesting.
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
naah - not really a problem - at least for playing around with.
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings. Also, they've been known
Or they get ratings that are actually real - not produced by someone
looking at a cap and thinking 'let's spec it to 100mA'.
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Been playing with my new induction device today, violating its specs.
:)
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Which is handy.
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
On a more DIY note - do you have any sources for the ferrite bars used to reduce the field under the pan?
be careful when working around the induction coil area if you have any
"Ian Stirling" <usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
Interesting.
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
naah - not really a problem - at least for playing around with.
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings.
Also, they've been known
Or they get ratings that are actually real - not produced by someone
looking at a cap and thinking 'let's spec it to 100mA'.
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Been playing with my new induction device today, violating its specs.
:)
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Which is handy.
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
On a more DIY note - do you have any sources for the ferrite bars used to reduce the field under the pan?
be careful when working around the induction coil area if you have any
form of metal wrist band devices on you. Watches, bracelets and even a
metal neck chain come to mind.
Dirk Bruere at NeoPax
Guest
Guest
Fri Mar 12, 2010 12:56 am
On 11/03/2010 20:42, Michael A. Terrell wrote:
Quote:
Dirk Bruere at NeoPax wrote:
On 11/03/2010 19:19, Michael A. Terrell wrote:
Dirk Bruere at NeoPax wrote:
On 11/03/2010 17:46, Ian Stirling wrote:
Tim Williams<tmoranwms_at_charter.net> wrote:
"Ian Stirling"<usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
Interesting.
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
naah - not really a problem - at least for playing around with.
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings.
Also, they've been known
Or they get ratings that are actually real - not produced by someone
looking at a cap and thinking 'let's spec it to 100mA'.
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Been playing with my new induction device today, violating its specs.
:)
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Which is handy.
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
On a more DIY note - do you have any sources for the ferrite bars used to reduce the field under the pan?
So, if you stick your head close do your metal fillings explode?
A modern version of the old 'Hot Foot'? ;-)
And wedding rings, metal watch straps etc
How resonant would a wedding ring or watch band be at 60 KHz? The
wavelength is 5,000 meters. A quater wave antenna would be 1,250
meters.
I've heated the tips of small screwdrivers to red heat at 100kHz
--
Dirk
http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show
Michael A. Terrell
Guest
Guest
Fri Mar 12, 2010 12:59 am
Tim Williams wrote:
Quote:
"Michael A. Terrell" <mike.terrell_at_earthlink.net> wrote in message
news:4B9955CE.775CEF98_at_earthlink.net...
And wedding rings, metal watch straps etc
How resonant would a wedding ring or watch band be at 60 KHz? The
wavelength is 5,000 meters. A quater wave antenna would be 1,250
meters.
What does "resonance" of a symmetric loop (it's not a loop antenna) have to
do with induction?
Efficiency.
--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'
Michael A. Terrell
Guest
Guest
Fri Mar 12, 2010 1:00 am
Dirk Bruere at NeoPax wrote:
Quote:
On 11/03/2010 20:42, Michael A. Terrell wrote:
Dirk Bruere at NeoPax wrote:
On 11/03/2010 19:19, Michael A. Terrell wrote:
Dirk Bruere at NeoPax wrote:
On 11/03/2010 17:46, Ian Stirling wrote:
Tim Williams<tmoranwms_at_charter.net> wrote:
"Ian Stirling"<usenet_at_mauve.plus.com> wrote in message
news:nrOdnawA0P55BhLWnZ2dnUVZ8nednZ2d_at_brightview.co.uk...
http://www.st.com/stonline/products/literature/an/12443.pdf
The above app-note uses 2*.68uF caps in parallel, for the
bridge.
Hmm, those are nice and tasty...
However - all the film caps I can seem to source easily
- digikey, mouser, rs, farnell, ... seem likely to promptly
explode - at least based on the datasheets, they sharply limit
voltage at high frequencies.
Nah, they won't explode -- hell, I've put 2A through some dinky MKPs (10mm
lead spacing) I found for cheap at Allied. No failures, although they did
get warm!
Interesting.
These Epcos parts (15mm lead spacing) are *rated* 2.3A, so I put a few
together for my induction heater:
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank7.jpg
200 x 0.1uF = 20uF, 250VAC, 460A (max. VAR at ~15kHz). I've had them up at
snip
That bank was only $70 in parts, but maybe you'd like something a little
less labor intensive.
naah - not really a problem - at least for playing around with.
But the ones in the chinese cookers are _MUCH_ smaller yet.
The Chinese don't need no steenkin' ratings.
Also, they've been known
Or they get ratings that are actually real - not produced by someone
looking at a cap and thinking 'let's spec it to 100mA'.
to be exactly as cheap as I am... I've seen more than a few Chinese
induction supplies that use a big mess of MKPs soldered on boards for the
tank cap!
Been playing with my new induction device today, violating its specs.
:)
Some rough calculation said that skin depth for non-magnetic stainless
at 50KHz was ~2.5mm.
As expected, most of my thick non-magnetic stainless steel pans diddn't
work at all.
I was not completely surprised to find that thin non-magnetic cookware -
bowls, pans, ... worked fine.
Which is handy.
Pondering modding it to add auto-simmer. (high power until noises indicate
boiling, then turn it down)
On a more DIY note - do you have any sources for the ferrite bars used to reduce the field under the pan?
So, if you stick your head close do your metal fillings explode?
A modern version of the old 'Hot Foot'? ;-)
And wedding rings, metal watch straps etc
How resonant would a wedding ring or watch band be at 60 KHz? The
wavelength is 5,000 meters. A quater wave antenna would be 1,250
meters.
I've heated the tips of small screwdrivers to red heat at 100kHz
They are a solid, not a small loop.
--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'
Ian Stirling
Guest
Guest
Fri Mar 12, 2010 1:06 am
Michael A. Terrell <mike.terrell_at_earthlink.net> wrote:
<snip>
Quote:
How resonant would a wedding ring or watch band be at 60 KHz? The
wavelength is 5,000 meters. A quater wave antenna would be 1,250
meters.
wavelength is 5,000 meters. A quater wave antenna would be 1,250
meters.
Resonance is not a factor at all.
At least in the load.
The induction cooker only uses a resonant circuit to reduce the drive
requirements, and EMI.
You can do a non-resonant stove - but you need 200A IGBTs, not 20A - for
example.
elektroda.net NewsGroups Forum Index - Electronics Design - Induction heating / cooking - and where to get low ESR high
