Joule Thief 101

[MileHigh]

I think a decent JT circuit would win this competition with the 555.  ONLY because it takes some energy to run the 555...and that is the only reason.

I am assuming that it would take tens of microwatts to run the 555 including the carefully selected timing components (the "overhead" not counting flashing the LED) and the equivalent overhead for the JT would be on the order of milliwatts.  So if you are talking about very long run times it may be an interesting competition.  Of course you would have to put the actual LED flashing on a level playing field.

There was a chip from the mid 1970s, the LM3909, that was also a very efficient LED flasher.  You can look it up.  In fact, it looks to me like it may be more efficient because it doesn't use any inductive components.  It might make for a three-way horse race.

[TinselKoala]

What are they made of, gold and diamond dust? The cheapest I can find LM3909 is around 4 dollars each, from china, and even in quantity. Some people want much more than that. My favorite Chinese vendor UTSource wants $31.25 for a lot of 5 (but has another listing for 1 for $4.00). Go figure.

A couple of sellers in the UK want over $17 for _one_ (but with free shipping.)

So I'm not going to be testing one any time soon, unless someone else donates one or two to me.

[TinselKoala]

Rob Paisley has "reverse engineered" the LM3909 so that it can be simulated with discrete components.

http://home.cogeco.ca/~rpaisley4/LM3909.html

Looks like an interesting project, but I still don't think it will compete with a JT. The Data Sheet for the LM3909 gives an "LED Boost" circuit that will drive an LED from 1.5 volt battery at 2 kHz... but it says it draws 4 mA.  Presumably that is an average, or equivalent-continuous, current drain. In which case, unless the LED is unusually brilliant.... well, it's not really that great.

[Pirate88179]

http://www.youtube.com/watch?v=wU5x8T2UkuI

Nice video TK, wow that is really small.  Very cool.

https://www.youtube.com/watch?v=iHmTc0PwiyY

Here is a vid from Ludic Science making a JT without a transistor.  He said he is replicating Lidmotor's circuit...I had forgotten about that one  This is pretty simple and cool.  I suppose it is really just a very simple and basic relay/solenoid  type device but man, I would have never thought of this in a million years.

Bill

Here is Lidmotor's original video:  https://www.youtube.com/watch?v=VjqBRXU3XnU

[TinselKoala]

Even smaller: