Joule Thief

[MarkE]

hi MarkE,
This is a interesting component which you recommended.
I did spot a seller in China is selling 10 pieces which output 5volts at $3.22USD with free shipment.
http://www.ebay.com/itm/10PCS-NCP1402SN50T1G-ON-IC-REG-BOOST-5V-0-2A-5TSOP-NEW-R5-/291114101279?pt=LH_DefaultDomain_0&hash=item43c7c0aa1f
Taking cost of other supporting smd components it would be around $1 to diy.

Yes, the parts are about a dollar in low qty.  The big cost is the printed circuit board blanks.  Even if you strip all the parts off of the SparkFun board, the $6. for the board is still pretty cheap for a single unit. 

[MarkE]

I have not as of yet fired up the 1402's but, I think I like the specs better than the 1400's.  At least, for what i am attempting to do.

I can't believe the price (cheap) on those sparkfun 1402 breakout boards.  It does not really say but do the components shown actually come with the pc board?  Or, is it just a board?  When I get paid, I will order a few of them.  (Thanks Mark E.)

All I am trying to do is have a small circuit that lights several leds and will run a battery down to .3 volts.  According to what I think I have read on their site, the sparkfun boards as shipped will not do that.  But, as mark suggested, I can manipulate my components onto the board and that would be a great, cheap, and easy way of prototyping.

Farmhand:

Thank you for your explanation of the 1402 hook-up.  You just saved me hours of work over here and I appreciate that.

Bill

It depends on what your application is.  The 1402's can deliver more power.  The 1400's are better suited to very low power and near zero standby.  The reason is that the 1400's work more like the solar LED stick lights:  They charge up the inductor and then completely dump it.  They do this at a fixed frequency, stopping if the voltage rises above the set-point.  The 1402's operate in a variable frequency mode, but require that the inductor remain in continuous conduction.  For any given input and output voltage, and inductor combination there is a minimum load current.  If you go below that minimum then the chip does not regulate.

Yes the SparkFun boards are completely assembled working units.

[Pirate88179]

It depends on what your application is.  The 1402's can deliver more power.  The 1400's are better suited to very low power and near zero standby.  The reason is that the 1400's work more like the solar LED stick lights:  They charge up the inductor and then completely dump it.  They do this at a fixed frequency, stopping if the voltage rises above the set-point.  The 1402's operate in a variable frequency mode, but require that the inductor remain in continuous conduction.  For any given input and output voltage, and inductor combination there is a minimum load current.  If you go below that minimum then the chip does not regulate.

Yes the SparkFun boards are completely assembled working units.

Mark:

Thanks for the info.  Wow, those boards are really cheap then.  Maybe I will get some 1400's and try those too.  I am trying to make a solar garden light type circuit without the solar cell and photosensor that will light some leds ( or even just one) and take the dead battery waaay down to where it is really dead.  From your info, the 1400's sound more like what I need but, I will try both.  I want the circuit to be small (I am off to a good start with that SOT-23 package!!) and use a minimum number of components which is why I got those axial inductors.  Upon closer inspection, it appears that the sparkfun board uses some type of smd inductor?  I didn't even know those were available.

Wow, so much to learn with all of this new stuff coming out.  I appreciate the help.

Bill

[TinselKoala]

3 LEDs in series, lighting brilliantly on less than 0.2 volts, finally go out at around 0.140 V or so:

http://www.youtube.com/watch?v=yjgemF5zpeE

Sorry, no hyperefficient SMDs in use, just discrete components and serendipity. Current draw? Well, to get power for practical light at those low voltages of course the current draw must be relatively high. But I think you can see that at 0.2 volts supply from the 1F capacitor the 3 series LEDs are definitely bright enough for some practical uses.

[Pirate88179]

Wow, 3 leds illuminated on that low voltage....nice work.  Just imagine what you might be able to do with some of these new hyperefficient smds?  Very impressive work TK.  Those leds were not just barely lit, they were all very bright and I know how hard that is to try to achieve.  I am thrilled to be able to light one led on .5 volts!

Great job,

Bill