On Tuesday, February 4, 2014 11:56:57 AM UTC-8, George Herold wrote:
> On Tuesday, February 4, 2014 2:26:34 PM UTC-5, mrda...@gmail.com wrote:
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> > A friend wanted to make a DC-DC converter for his daughers' science project, which involves making an LED torch out of a hand-held Peltier tile.
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> > I suggested he look into the Joule Thief, which he did.
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> > He says it works, but he'd prefer for it to work at 0.3V instead of 0.7V.
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> > I then remembered the germanium transistors. When he asked where to find one, I realized they're so old they don't come in plastic TO-92 cases, and they all seem to be PNP when I look on eBay.
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> > Is there any modern transistor that has a Vbe of circa 0.3V? Or are we stuck looking for decades-old NPN germanium transistors on eBay?
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> > Thanks,
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> > Michael
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> Hmm who is doing the project?
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> Anyway googling low voltage DC-DC converter I found this,
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> http://www.digikey.com/us/en/techzone/energy-harvesting/resources/articles/Low-voltage-DC-DC-Converters-Build-Efficient-Power-Management.html
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> George H.
Haha, we went to Uni together and still chat every now and then, and actually he gave me a schematic very similar to what you just posted! Then I said, "Joule Thief." Much simpler than a dedicated IC...
Thanks!
Reply by ●February 4, 20142014-02-04
On Tuesday, February 4, 2014 11:59:05 AM UTC-8, Tim Wescott wrote:
> On Tue, 04 Feb 2014 11:26:34 -0800, mrdarrett wrote:
>
>
>
> > A friend wanted to make a DC-DC converter for his daughers' science
>
> > project, which involves making an LED torch out of a hand-held Peltier
>
> > tile.
>
> >
>
> > I suggested he look into the Joule Thief, which he did.
>
> >
>
> > He says it works, but he'd prefer for it to work at 0.3V instead of
>
> > 0.7V.
>
> >
>
> > I then remembered the germanium transistors. When he asked where to
>
> > find one, I realized they're so old they don't come in plastic TO-92
>
> > cases, and they all seem to be PNP when I look on eBay.
>
> >
>
> > Is there any modern transistor that has a Vbe of circa 0.3V? Or are we
>
> > stuck looking for decades-old NPN germanium transistors on eBay?
>
>
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> Turn the circuit upside down and use a PNP germanium. Make sure it has a
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> sufficient current rating.
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> Or, look here: https://en.wikipedia.org/wiki/Joule_thief#Competing_systems
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> I was going to suggest a JFET, but didn't know if it'd work. I guess I
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> have my answer.
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> --
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> Tim Wescott
>
> Wescott Design Services
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> http://www.wescottdesign.com
On Tue, 04 Feb 2014 11:26:34 -0800, mrdarrett wrote:
> A friend wanted to make a DC-DC converter for his daughers' science
> project, which involves making an LED torch out of a hand-held Peltier
> tile.
>
> I suggested he look into the Joule Thief, which he did.
>
> He says it works, but he'd prefer for it to work at 0.3V instead of
> 0.7V.
>
> I then remembered the germanium transistors. When he asked where to
> find one, I realized they're so old they don't come in plastic TO-92
> cases, and they all seem to be PNP when I look on eBay.
>
> Is there any modern transistor that has a Vbe of circa 0.3V? Or are we
> stuck looking for decades-old NPN germanium transistors on eBay?
On Tuesday, February 4, 2014 2:26:34 PM UTC-5, mrda...@gmail.com wrote:
> A friend wanted to make a DC-DC converter for his daughers' science project, which involves making an LED torch out of a hand-held Peltier tile.
>
>
>
> I suggested he look into the Joule Thief, which he did.
>
>
>
> He says it works, but he'd prefer for it to work at 0.3V instead of 0.7V.
>
>
>
> I then remembered the germanium transistors. When he asked where to find one, I realized they're so old they don't come in plastic TO-92 cases, and they all seem to be PNP when I look on eBay.
>
>
>
> Is there any modern transistor that has a Vbe of circa 0.3V? Or are we stuck looking for decades-old NPN germanium transistors on eBay?
>
>
>
> Thanks,
>
>
>
> Michael
A friend wanted to make a DC-DC converter for his daughers' science project, which involves making an LED torch out of a hand-held Peltier tile.
I suggested he look into the Joule Thief, which he did.
He says it works, but he'd prefer for it to work at 0.3V instead of 0.7V.
I then remembered the germanium transistors. When he asked where to find one, I realized they're so old they don't come in plastic TO-92 cases, and they all seem to be PNP when I look on eBay.
Is there any modern transistor that has a Vbe of circa 0.3V? Or are we stuck looking for decades-old NPN germanium transistors on eBay?
Thanks,
Michael