Joule Thief

[NickZ]

  Skywatcher and All:
   The TIP31 is a single transistor, not a pair, but it has a higher voltage rating than most, so it can handle the most juice without overheating and burning out.  I don't understand the comparison with the darlington pair. 
   The point of replicating Koolers bwjt circuits is because it has been shown to work in all other devices that he has built.  He states that he has built a hundred of them. What this probably means is that he has spent more time, and energy in developing this particular circuit, than all of us combined.
I don't have the right cores, and without them the 70 leds lighting on such low draw, or the 5 month running units can't be replicated. At least I have not been able to do so, using my more inferior iron powder cores, as well as some ferrite ones as well.  That does not mean that others can't equal his outstanding results. The circuit is very simple, but there may be certain things like the 'special diodes' and such that make it unique. He's probably laughing at me trying to explain the benefits and disadvantages of his circuits.  But I'm afraid that possibly something has happened to him, as he would have called home (here) by now. 
   

[WilbyInebriated]

  Skywatcher and All:
   The TIP31 is a single transistor, not a pair, but it has a higher voltage rating than most, so it can handle the most juice without overheating and burning out.  I don't understand the comparison with the darlington pair. 

the tip31's i have are darlingtons albeit they are on a single die.
http://www.newark.com/fairchild-semiconductor/tip31/darlington-transistor-npn-40v-to/dp/58K2425

[SkyWatcher123]

Hi folks, Hi willy, I picked up the tip31 from radiohut and the package does not say darlington nor does the website. I wonder if they are different or the same. Seem to have the same specs as the link you posted.
Otherwise, it is working pretty well for my setup, darlington or not.
Oh and i did try koolers circuit type and it is about the same.
peace love light
tyson

[poynt99]

the tip31's i have are darlingtons albeit they are on a single die.
http://www.newark.com/fairchild-semiconductor/tip31/darlington-transistor-npn-40v-to/dp/58K2425

Newark (now "element 14") screwed up on that page. If you scroll down you'll see a NTE196 substitute data sheet. It is not a Darlington transistor.
http://www.nteinc.com/specs/100to199/pdf/nte196.pdf

Here is the datasheet for the TIP31 series:
http://people.ece.cornell.edu/land/courses/ece4760/FinalProjects/s2007/aw259_bkr24/TIP31.pdf

.99

PS. Darlingtons in the TIP series start at TIP100.
http://www.futurlec.com/TransPowerTIP.shtml

[NickZ]

  POINT:
   Thanks for clearing that up.  MY TIP31 was bought at radio shack, but what you actually get is some other compatible transistor made who know where.  Radio shack does not mention Darlington on the box, or on their add on it. This is their description of it:
   http://www.radioshack.com/product/index.jsp?productId=2062610

   The one I have works great, but is a real hog on batteries.