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What material is ideal for low-power Joule Thief inductor cores?
Ferrite, or powdered iron? Is an air gap desired, or not?
I saw an ad for a "high permeability" toroid but the material was not specified; besides, how high is high, anyway?
Thanks,
Michael
On Tuesday, February 4, 2014 5:24:26 PM UTC-5, mrda...@gmail.com wrote:
What material is ideal for low-power Joule Thief inductor cores?
Ferrite, or powdered iron? Is an air gap desired, or not?
I saw an ad for a "high permeability" toroid but the material was not specified; besides, how high is high, anyway?
Thanks,
Michael
Knowing little about magnetic's, I'd say no gap.. its a transformer.
And the material choice depends on the frequency. Higher freq -> higher resistivity. (the higher resistivity ferrites also have lower permeability.)
In practice just grab what ever toroid is around.
George H.
In practice just grab what ever toroid is around.
Uhhh...
Without doing the analysis myself I can't say, but you want to check to
see how much flux is building up in the critter, and make your decisions
accordingly. I haven't memorized which switching topology wants what,
but some benefit from a gapped inductor, and some don't.
It depends on whether the energy is being stored in the core between half-
cycles (in which case you want a gap) or getting transferred to the load
at the same instant that it's going into the primary. The former stores
the energy in the flux, and benefits from a gapped core, because an air
gap can store way more energy than ferrite. The latter can have a plain
ol' ungapped core.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
On Tuesday, February 4, 2014 5:24:26 PM UTC-5, mrda...@gmail.com wrote:
What material is ideal for low-power Joule Thief inductor cores?
Ferrite, or powdered iron? Is an air gap desired, or not?
I saw an ad for a "high permeability" toroid but the material was not
specified; besides, how high is high, anyway?
Thanks,
Michael
Knowing little about magnetic's, I'd say no gap.. its a transformer.
And the material choice depends on the frequency. Higher freq -> higher
resistivity. (the higher resistivity ferrites also have lower
permeability.)
In practice just grab what ever toroid is around.
It depends on whether the energy is being stored in the core between half-
cycles
(in which case you want a gap) or getting transferred to the load
at the same instant that it's going into the primary. The former stores
the energy in the flux, and benefits from a gapped core, because an air
gap can store way more energy than ferrite.
On Tue, 04 Feb 2014 15:07:59 -0800, George Herold wrote:
On Tuesday, February 4, 2014 5:24:26 PM UTC-5, mrda...@gmail.com wrote:
What material is ideal for low-power Joule Thief inductor cores?
Ferrite, or powdered iron? Is an air gap desired, or not?
I saw an ad for a "high permeability" toroid but the material was not
specified; besides, how high is high, anyway?
Thanks,
Michael
Knowing little about magnetic's, I'd say no gap.. its a transformer.
And the material choice depends on the frequency. Higher freq -> higher
resistivity. (the higher resistivity ferrites also have lower
permeability.)
In practice just grab what ever toroid is around.
Uhhh...
Without doing the analysis myself I can't say, but you want to check to
see how much flux is building up in the critter, and make your decisions
accordingly. I haven't memorized which switching topology wants what,
but some benefit from a gapped inductor, and some don't.
It depends on whether the energy is being stored in the core between half-
cycles (in which case you want a gap) or getting transferred to the load
at the same instant that it's going into the primary. The former stores
the energy in the flux, and benefits from a gapped core, because an air
gap can store way more energy than ferrite. The latter can have a plain
ol' ungapped core.
Oops, thanks for the correction Tim. I sometimes think I shold just keep my mouth shut. But I can also learn, if I say somethng stupid.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
What material is ideal for low-power Joule Thief inductor cores?
Ferrite, or powdered iron? Is an air gap desired, or not?
I saw an ad for a "high permeability" toroid but the material was not specified; besides, how high is high, anyway?
Thanks,
Michael
On Tue, 04 Feb 2014 18:29:26 -0800, mrdarrett wrote:
On Tuesday, February 4, 2014 5:16:27 PM UTC-8, Tim Wescott wrote:
...
In practice just grab what ever toroid is around.
Uhhh...
Without doing the analysis myself I can't say, but you want to check to
see how much flux is building up in the critter, and make your
decisions
accordingly. I haven't memorized which switching topology wants what,
but some benefit from a gapped inductor, and some don't.
It depends on whether the energy is being stored in the core between
half-
cycles (in which case you want a gap) or getting transferred to the
load
at the same instant that it's going into the primary. The former
stores
the energy in the flux, and benefits from a gapped core, because an air
gap can store way more energy than ferrite. The latter can have a
plain
ol' ungapped core.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Ok thanks!
I tried building one a couple of years ago, and when it didn't work I
thought it was because I had the wrong kind of core... (from a choke?)
The wrong kind of core would probably just make things inefficient; it'd
have to be really bad to make the thing refuse to work entirely.
I think the dotted end of the coil is wrong in the Wikipedia article. If
you put the dot next to the collector and next to the base, then you have
a Hartley oscillator that uses the stray capacitance of the transistor
and coil to establish "resonance" (in quotes because it's not _very_
resonant).
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Some manufacturers consider de J110 obsolete. Some others still offer them.
The SMD variant seems to be widely available. Look at Mouser and RS for
instance.
petrus bitbyter
On Tuesday, February 4, 2014 5:16:27 PM UTC-8, Tim Wescott wrote:
...
In practice just grab what ever toroid is around.
Uhhh...
Without doing the analysis myself I can't say, but you want to check to
see how much flux is building up in the critter, and make your
decisions
accordingly. I haven't memorized which switching topology wants what,
but some benefit from a gapped inductor, and some don't.
It depends on whether the energy is being stored in the core between
half-
cycles (in which case you want a gap) or getting transferred to the
load
at the same instant that it's going into the primary. The former
stores
the energy in the flux, and benefits from a gapped core, because an air
gap can store way more energy than ferrite. The latter can have a
plain
ol' ungapped core.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Ok thanks!
I tried building one a couple of years ago, and when it didn't work I
thought it was because I had the wrong kind of core... (from a choke?)
The wrong kind of core would probably just make things inefficient; it'd
have to be really bad to make the thing refuse to work entirely.
I think the dotted end of the coil is wrong in the Wikipedia article. If
you put the dot next to the collector and next to the base, then you have
a Hartley oscillator that uses the stray capacitance of the transistor
and coil to establish "resonance" (in quotes because it's not _very_
resonant).
On Wednesday, February 5, 2014 9:29:56 AM UTC-8, Tim Wescott wrote:
On Tue, 04 Feb 2014 18:29:26 -0800, mrdarrett wrote:
On Tuesday, February 4, 2014 5:16:27 PM UTC-8, Tim Wescott wrote:
...
In practice just grab what ever toroid is around.
Uhhh...
Without doing the analysis myself I can't say, but you want to check
to
see how much flux is building up in the critter, and make your
decisions
accordingly. I haven't memorized which switching topology wants what,
but some benefit from a gapped inductor, and some don't.
It depends on whether the energy is being stored in the core between
half-
cycles (in which case you want a gap) or getting transferred to the
load
at the same instant that it's going into the primary. The former
stores
the energy in the flux, and benefits from a gapped core, because an
air
gap can store way more energy than ferrite. The latter can have a
plain
ol' ungapped core.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Ok thanks!
I tried building one a couple of years ago, and when it didn't work I
thought it was because I had the wrong kind of core... (from a choke?)
The wrong kind of core would probably just make things inefficient; it'd
have to be really bad to make the thing refuse to work entirely.
I think the dotted end of the coil is wrong in the Wikipedia article. If
you put the dot next to the collector and next to the base, then you have
a Hartley oscillator that uses the stray capacitance of the transistor
and coil to establish "resonance" (in quotes because it's not _very_
resonant).
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Oh neato! Thanks!
An autotransformer should work fine too, right?
The J110 jfet seems to be obsolete. I'm reading the specs on the J111 but
am not sure what the continuous drain current is. Is it 20 mA (Idss)?
http://www.fairchildsemi.com/ds/J1/J111.pdf
Michael
Look for joule thief on this site
http://www.talkingelectronics.com/te_interactive_index.html
lot of information
What material is ideal for low-power Joule Thief inductor cores?
Ferrite, or powdered iron? Is an air gap desired, or not?
I saw an ad for a "high permeability" toroid but the material was not
specified; besides, how high is high, anyway?
Thanks,
Michael