Joule Thief

[WilbyInebriated]

thanks for your stunningly helpful comment... what an amazing contribution to the discussion at hand   
yeah thaelin, if you found any mistakes in my comments please feel free to mention where.

[Pirate88179]

Hey, I finally had some time and rewired my Joule thief and it works great!  It is running a large ultra bright led from a single AA bat. and it is what I would call bright. (Very bright)  I used the 2N3904 transistor for this one but I will fool around with some of the others that you guys mentioned. I had wired the wires from the ferrite incorrectly.  Instead of connecting 2 wires together, one from each side of the toroid, I had connected 2 from the same side and it did not work. (Duh)

We are having an ice storm here today but, when I get the time, I will test this out on my earth battery to see if it works the same as with the AA.

I really appreciate all of the information supplied here from you guys.  From what I have read here, and on the net, these have been around for some time.  what I don't understand is...if I were designing and marketing a small flashlight of some kind, why would I not add this circuit to it so it could run longer and on "dead" batteries?  Seems to me to be a good selling point.  I know the transistor is pulsing the power and now I wonder what else might also run successfully on pulsed power as well?  Probably not a clock.  Small motors maybe?  Little fans like computer fans?

I know it does not take all that much to impress me these days, but I really like this circuit.

Bill

[WilbyInebriated]

nice job bill! success is always fun
keep playing with it and remember, newer is not always better. 

[Walter Hofmann]

Hi all,
maybe you can try this IC from linear
http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1094,C1766,P80613,D26511
greetings
walt

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

[Pirate88179]

@ All:

I decided to post 2 pictures of my joule thief.  I forgot to mention that I used a 10mm 28,000 mcd LED (white) which calls for 3.5-4 v and 20 mA to operate.  The photo with it illuminated does not let you see the single AA battery but, it is there.  I thought it would show up but the led is so bright, my shutter blocked out a lot of light surrounding it.

I just found out Ace hardware is selling a string of Christmas led lights with 36 leds and the transformer for $3.99 US.  Heck, I paid almost that much for the 1 led from Radio Shack!!!  I am going to pick up some to play with.

Bill