Joule Thief

[spinner]

I think this one is one of the easiest... ANY (even "dead") single cell battery (0,9V-2V), IC, inductor, and a LED(s) (it works nicely with a few microHenry SMD "choke"...)..  and, it's 80% efficient...

http://www.prema.com/pdf/pr4401.pdf

Yes, it has limitations, allright....

Anyway, there are many DC/DC chip converters on the market, ranging from mW to many Watts of power...

Check out Wilby's link (on page 3?), too...

[Pirate88179]

@ Spinner:

Wow, thanks!  If I read that correctly, 55 hours off a single AA bat?  That sounds pretty efficient to me.  Can we find these for sale in small quantities?  I have not searched on the net yet but will.  My local Radio Shack carries next to nothing in the component dept.  I wonder how these would work with the earth batteries?  Thanks for posting this.

Bill

[WilbyInebriated]

???Yes they are. 
Why would they (manufacturers) lie about it? Take, for instance, PR4401. It's efficiency is declared under certain conditions, and it can provide a continuous power at #82% (ENERGY EFFICIENCY)!. Try to adopt the circuit discussed in this thread to the same conditions (add rectifying/smoothing, etc..), and see how it will perform....

Or, take a two identical supercaps charged to the same Voltage, and see how long the LEDs will work  with both circuits.... Or, find an equivalent serial ic circuit with a PWM output capability... Or,... Whatever...
You're aware that we're comparing a +50 years old electro-tech components against a few years old? I'm sure there's at least some improvement being made....

BTW, Thanks for providing the link... It is a good text, telling a lot about LEDs and suitable LV driving circuits...

As you may have noticed, the author never claims OU. And the only efficiency he's talking about is based on a "personal" light intensity perceptions (not correct measurements). Need I say more?

Thanks.. Can you provide a circuit schematics and description/details of a measuring procedure?
The "extra smoothing cap" ALWAYS lowers the combined circuit efficiency... Voltage without current cannot do much work...

OK, i admitted before that we're "not looking through the same glasses"...

Cheers!

yes they are? wanna post your math for this?
you obviously read the link, you referred bill to it... so you must have missed this part about your super efficient pr4401?

"With this we turn to a surface-mount chip that has been designed to carry out the exact same task as circuit B. The chip is called PR4401. 
I could not find any sales literature on the internet, but the manufacturer requires 9,000 pieces to be bought at a cost of 36 cents per piece. This comes to $3,240 if you want to incorporate it into your project.
I have described the pro's and con's of this chip in another article "Circuit Tricks" and you should read the features and work out what they really mean.
When you build circuit "B," you will realize the specifications given in the .pdf for the chip, could be improved. We have achieved a supply current of 18mA for an equivalent brightness of 10mA. The chip requires 25mA. So, all the technology in the world has not surpassed a hand-made circuit."

outperforms by a factor of 2 huh?
and i'm gonna fathom a guess that you also missed the 'circuit tricks' article...

"Now we come to a critical analysis of the chip.
1. The data for the chip states it will operate for 55 hours at 33mA, on a single AA alkaline cell, for an end-voltage of 0.9v. This gives a consumption of 1815mAhr.  The capacity of an AA alkaline cell is 2400mAhr when taken to a terminal voltage of 0.8v.
This means the chip is using only 75% of the capacity of the cell.
2. The second point to note is the maximum input voltage for the chip. This is 1.9v.
The chip will not trigger or start properly if the supply voltage is above 1.9v.
This is a big limitation. How many projects work from a single cell? If the chip was designed to operate from 2 cells (3v), the terminal voltage (meaning the end-voltage) could be as low as 1v and this would mean each cell could be used to an end-voltage of 0.5v. This would almost double the number of hours per cell, giving a total of more than 200 hours from two cells.
3. The cost of the chip is about 36 cents when buying 9,000 IC's. This is an outlay of more than $3,200 for a single item.
The cost is too high when you consider its function. It should be less than 8 cents. When you see the Chinese using the chip in a project, you know the price is right. I will wait for this to happen.
4. No supplier for the chip could be found on the internet and the other components (inductor and surface-mount white LED) are also difficult to buy as a single item.
I searched the internet for 3 hours and could not find a supplier or price for the IC. I finally had to contact the manufacturer. Their minimum order was 9,000 pieces!!!!
5. The chip shuts down when the cell voltage reaches 0.9v. This is to prevent deep discharge. This is ok for a rechargeable cell as some have a "memory" and should not be fully discharged, but an alkaline cell can be fully used-up before it is thrown away. Why not use the maximum energy from this type of cell?
6. Their .pdf document for the PR4401 had a number of technical inaccuracies and I wrote to them with the corrections. Up to this point in time, I have not received a reply!!"

limitations indeed. and you think this is one of the 'easiest'?, you can't even buy them, unless you want to drop a couple grand... i guess it also says something about taking datasheets at face value, why would they lie? dunno, maybe cause they are trying to sell them... come on captain obvious, that one is obvious. says something about actually doing the experiment and taking your own measurements, need i say more?

btw, thanks for letting us all know that a simple blocking oscillator is not OU, even though no one claimed it was... captain obvious strikes again

[Trino Cularoid]

PR4401 (Google translation)
One Volt LED
[all links above]

[Thaelin]

   This one's for Willy:
        Since you like to flip the bone, here is you one.

Just couldn't help my self.     

If its too bold stephan, just delete it.

thaelin