Joule Thief

[Pardon]

Iwas just looking arround and found this interesting thing

With PR4402 PREMA Semiconductor offers the next IC in a family of 0.9V LED boost drivers, operating white LEDs from one battery cell. While PR4401 is best suited for LED currents of up to 20mA, PR4402 is capable of 40mA. The current is set by the inductor value, resulting in a low number of external components. Applications are pocket torches, key ring pendants or head lights and LCD back lighting in single-cell devices like MP3 players.

The one-cell battery operation is very attractive. It allows design of smaller and light weighted products at lower cost. In multiple-cell operation of rechargeable batteries often one cell can be destroyed by a deep discharge. With the PR4401/4402 there is no more reason for using several battery cells or for implementing the classical light bulb. With one battery cell and depending on the application one inductor only as external component, a very small-sized circuitry can be realized with the PR4401/4402, both SOT23 packaged. The driven LED current is almost independent from the supply voltage, which guarantees a constant brightness even with a discharging battery.

[Pirate88179]

Altrez:

Great job!  These things are great once you get them to work, and now that you have...there will be no stopping you.  Way to go!

@ Pardon:

Great find there.  Am I mistaken or is this a kind of solid state joule thief?  If it is, I wonder how its efficiency compares to some of the ones we have here?  Possibly someone else knows more about this than I, which would not be hard to do.  Thanks for bringing this to our attention.

Bill

[jeanna]

@Pardon,
Interesting find. I think this backs up what we are doing. Whoknows maybe it is one of us? I am glad to see it. Sometimes, for inventors the hardest thing is to stop long enough to bring something to market. good for them.

@All,
I am charging the batteries for the scope... so

I pulled the precision pot out of the bag and tuned my MK2.
It was going along fine then the LED blew.
oops
I forgot to take it out! oh well, the voltage kept going up to 26.3V rectified shown on the bridge.

The resistor ended up being 204ohm. (I may start again at the high end.) If I find another sweet spot, I will report.

The part I forgot to change before I did this was the 2 wires of one pickup side in on the breadboard in parallel. I guess the amps must have blown the led. I don't think it got too close before, or maybe I wasn't able to hold that precise resistance amount long enough to blow the light before. oh well. another day another dollar, as they say. Too bad it really is a dollar to replace these things.

I did get some 65centers from allelectronics to try. They are not as bright but really ok. I think 4 or 5 in a cluster going in different directions inside an old frosted bulb may look pretty bright. Well, that is down the road a bit.

So, to recap this calamitous report
2N3904
MK2 wound primary 4T,5T pickups as follows:12 up 13 down on one side of primary, 12 up 13 down on other side. (so 25 each)
and using all 4 pickups, but 2 sets of each from a side lighting leds and
204 ohm base resistor
Rectified volts 26.3V - can only check one at a time.
Amps draw without lights 29.7mA
Amps draw on 2^o with light that blew 43mA
Amps draw on whole ckt with all secondaries and 2 lights 27.6mA
as you can imagine the lights are blazing (until they blow  )


This is not yet enough for a cfl, but it is getting there!

jeanna

[gadgetmall]

Iwas just looking arround and found this interesting thing

With PR4402 PREMA Semiconductor offers the next IC in a family of 0.9V LED boost drivers, operating white LEDs from one battery cell. While PR4401 is best suited for LED currents of up to 20mA, PR4402 is capable of 40mA. The current is set by the inductor value, resulting in a low number of external components. Applications are pocket torches, key ring pendants or head lights and LCD back lighting in single-cell devices like MP3 players.

The one-cell battery operation is very attractive. It allows design of smaller and light weighted products at lower cost. In multiple-cell operation of rechargeable batteries often one cell can be destroyed by a deep discharge. With the PR4401/4402 there is no more reason for using several battery cells or for implementing the classical light bulb. With one battery cell and depending on the application one inductor only as external component, a very small-sized circuitry can be realized with the PR4401/4402, both SOT23 packaged. The driven LED current is almost independent from the supply voltage, which guarantees a constant brightness even with a discharging battery.

Hi . I saw these a few months back . they are very inefficiant . As you can see in the forum here we are running 10,000 mcd Leds with .0.20 milliamps at .20 volts off a JT ..

Gadget //

[gadgetmall]

@Pardon,
Interesting find. I think this backs up what we are doing. Whoknows maybe it is one of us? I am glad to see it. Sometimes, for inventors the hardest thing is to stop long enough to bring something to market. good for them.

@All,
I am charging the batteries for the scope... so

I pulled the precision pot out of the bag and tuned my MK2.
It was going along fine then the LED blew.
oops
I forgot to take it out! oh well, the voltage kept going up to 26.3V rectified shown on the bridge.

The resistor ended up being 204ohm. (I may start again at the high end.) If I find another sweet spot, I will report.

The part I forgot to change before I did this was the 2 wires of one pickup side in on the breadboard in parallel. I guess the amps must have blown the led. I don't think it got too close before, or maybe I wasn't able to hold that precise resistance amount long enough to blow the light before. oh well. another day another dollar, as they say. Too bad it really is a dollar to replace these things.

I did get some 65centers from allelectronics to try. They are not as bright but really ok. I think 4 or 5 in a cluster going in different directions inside an old frosted bulb may look pretty bright. Well, that is down the road a bit.

So, to recap this calamitous report
2N3904
MK2 wound primary 4T,5T pickups as follows:12 up 13 down on one side of primary, 12 up 13 down on other side. (so 25 each)
and using all 4 pickups, but 2 sets of each from a side lighting leds and
204 ohm base resistor
Rectified volts 26.3V - can only check one at a time.
Amps draw without lights 29.7mA
Amps draw on 2^o with light that blew 43mA
Amps draw on whole ckt with all secondaries and 2 lights 27.6mA
as you can imagine the lights are blazing (until they blow  )


This is not yet enough for a cfl, but it is getting there!

jeanna

Hello Jeanna . Yea after Blowing every white led i had practically i decided to hook up a few strings of 200 white leds on my mk2 . Its lights them Bright .! But im sad cause i blew My Daughters Jewel Thief so im working on another one . Dont try to run another Jt with an led with mk2. it will flash like a camera flash.

Gadget