Pictures of the Internet's Largest Joule Thief

Whoops,

Here's the array, assembled:

LEDs on collector/inductor. Worked right off the bat. Waveform showed kind of weird turn-on behavior though: Reducing the series base resistance cleaned that up. Overshoot on the collector waveform is mostly due to the long emitter lead (these waveforms were measured with respect to the emitter, at the package), which made about a 1/2" loop. I fixed that.

The revision: trying it with a schottky rectifier.

Glowing:

View of the new hardware:

10uF ceramic chip is the tan blob just left of the schottky, which is a Shidengen M2FH3. Collector waveform is a clean, flat square wave with little overshoot, 2V peak to peak. Output was a constant 1.85V with under 10% ripple -- the LEDs have a pretty high impedance relative to that big-stinkin'-ceramic-which-is-actually-small-stinkin'-SMT. A little overshoot on switching, of course, but really only an artifact of the wiring.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

On a sunny day (Fri, 26 Dec 2008 13:42:39 -0600) it happened "Tim Williams" wrote in :

What sort of current does it draw from the battery?

(snip)

Very much in season! "Kling, circuit, kling-a-ling-a-ling..." (to paraphrase a German Christmas carol)

Yet another Christmas carol! "Hark! The al-ca-line is shreaking..." ;-)

Tim Williams schrieb:

...

Hi, what kind of transistor is this KSC5001 (okay, npn BJT): I couldn't find any datasheets on the Internet?

CU

Reinhard

KSC is Kennedy Space Center. Not to be confused with KFC, aka 'Kentucky Fried Colonel". ;-)

--
http://improve-usenet.org/index.html

aioe.org, Goggle Groups, and Web TV users must request to be white
listed, or I will not see your messages.

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm


There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you\'re crazy.

The OP lied.

Ermm....

KTC I think?

The classic 2SC works, too.

Tim

-- Deep Friar: a very philosophical monk. Website:

Tim Williams schrieb:

Hello Tim

Thank you very much: now I could find a datasheet :-)!

Perhaps you might think about correcting the schematic to avoid similar questions in the future ...

Best regards

Reinhard

Neat. I've been away--sorry to have missed your earlier question about windings. Yours look ample.

10% voltage ripple means a _lot_ of current ripple feeding an LED load. A bigger filter cap would save wastage in the LEDs' e.s.r.

Any measurements? Pout/Pin ? Updated waveforms?

Cheers, James Arthur