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Author Topic: High Efficiency LED for Joule Thief, etc.  (Read 12771 times)

Offline TinselKoala

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High Efficiency LED for Joule Thief, etc.
« on: August 14, 2015, 08:35:07 AM »
Here's something I've been playing around with. It's a high-efficiency LED,  Philips Lumileds MXA7-PW57-H001, coupled with a AP2502 current-sink regulator chip. The AP2502 has 4 current-sink outputs each regulated to sink 20 mA. So over the supply voltage range of 2.9 to 6 volts, it will keep 20 mA current flowing in the LED, per output. I'm only using one output and one LED here. The chip also has an Enable pin which allows PWM modulation of brightness by varying the duty cycle of the voltage applied to the pin. The chip eliminates the need for a power-wasting series resistor to regulate current. The LED is just about the highest efficiency LED available on the market.

The parts were kindly sent to me by a friend.

I'll be doing some more tests with these devices as time goes by. It will be very interesting to see how long a single CR2032 button cell will keep this LED glowing intensely brightly at 20 mA. The LED is actually nowhere near full brightness at 20 mA; at 100 mA it is blindingly bright, obscenely bright. 

http://www.youtube.com/watch?v=BtcF2aMC_ew
http://www.youtube.com/watch?v=X9wxuRZV-Ro

The LEDs and the current-sink chip are available from DigiKey. The LEDs cost about 70 cents US for a single one, or about 10 dollars for 25 of them. The AP2502 is about the same price. These are both surface mount devices. SparkFun sells a breakout board for SOT-23-6 devices for about a dollar each, that will turn the tiny chip into a standard 6-pin DIP footprint.

Free Energy | searching for free energy and discussing free energy


Offline MarkE

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #1 on: August 14, 2015, 08:55:54 AM »
Each of the pins 3, 4, 5, and 6 sink 20mA when pin 1 is high.  The AP2502 is intended to be used as an area back light driver.


Offline TinselKoala

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #2 on: August 14, 2015, 09:05:26 AM »
Each of the pins 3, 4, 5, and 6 sink 20mA when pin 1 is high.  The AP2502 is intended to be used as an area back light driver.
So the chip must be operating its output mosfets in the linear region, yes? With Enable tied 100 percent High, the LEDs aren't pulsed, I don't think, so current regulation must be accomplished by the op-amps regulating the voltage to the Gates of the mosfets as the LED supply voltage is varied. Is that right?

Offline MarkE

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #3 on: August 14, 2015, 09:32:01 AM »
So the chip must be operating its output mosfets in the linear region, yes? With Enable tied 100 percent High, the LEDs aren't pulsed, I don't think, so current regulation must be accomplished by the op-amps regulating the voltage to the Gates of the mosfets as the LED supply voltage is varied. Is that right?
Yes, that is how the device works.  The idea is that if you have a lithium battery that is nominally 3.6V in a hand-held product, then you get good efficiency by just linear regulating to a white LED that can run on 2.9V.  Most of the time the battery will be between 3.4V and 3.7V giving you 78% - 85% efficiency in a small space at really low cost. 

JT circuits are current sources of sorts so they don't need the additional regulator to protect the LED.  The regulator flattens the flyback voltage down slope, converging rms and average LED current, increasing efficiency.  Depending on the LED parameters and the particular JT design, the regulator can realize increased net efficiency. 

Those cheapy blue oval flash lights from Harbor Freight just use a simple current limiting resistor.  So, they are quite inefficient and the brightness starts dropping sharply in less than an hour.  A current regulator of any kind makes that better.  A high efficiency switching regulator is more ideal.  A pair of those clip-on 1.5V regulators that have been overhyped would work great with the board that you have.  The efficiency after those regulators would be about 180 lumens per Watt.


Online ramset

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #4 on: August 14, 2015, 01:33:58 PM »
Tinsel
A sizzling Topic ATM ...
Think PINK
I am very Happy to see "you" working on this .

https://www.youtube.com/watch?v=ILzWmw53Wwo

http://www.terraspheresystems.com/index.php/news-media/19-news/41-urban-farming-20-no-soil-no-sun
From Above link  I square ft of Vertical farming WILL YIELD 64 head of lettuce per arum, where as 1 square foot of Land farming
?? MAY ??   yield 3 heads per anum.[Ideal conditions]

Establishing Crop yields per square foot against energy required to run the LED's would be wonderful to know ,do they have to run at full power ?
I do understand that PWM would NOT be acceptable for growing crops ,you can trick the eye But not mother nature [thx Brad].
Or would PWM be appropriate for part of the plants 24/7 365 artificial day ??

This is the future.....

Chet K


Free Energy | searching for free energy and discussing free energy

Re: High Efficiency LED for Joule Thief, etc.
« Reply #4 on: August 14, 2015, 01:33:58 PM »
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Offline MarkE

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #5 on: August 14, 2015, 01:50:49 PM »
Tinsel
A sizzling Topic ATM ...
Think PINK

https://www.youtube.com/watch?v=ILzWmw53Wwo

http://www.terraspheresystems.com/index.php/news-media/19-news/41-urban-farming-20-no-soil-no-sun
From Above link  I square ft of Vertical farming WILL YIELD 64 head of lettuce per arum, where as 1 square foot of Land farming
?? MAY ??   yield 3 heads per anum.[Ideal conditions]

Establishing Crop yields per square foot against energy required to run the LED's would be wonderful to know ,do they have to run at full power ?
I do understand that PWM would NOT be acceptable for growing crops ,you can trick the eye But not mother nature [thx Brad].
Or would PWM be appropriate for part of the plants 24/7 365 artificial day ??

This is the future.....

Chet K
The reduction in water consumption and transportation requirements are really the big factors.  You can get a feel for the amount of LED power needed by the density of the lighting in the video.

Online ramset

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #6 on: August 14, 2015, 03:29:15 PM »
Typical comments from Big business attempts / failures  in this area have MUCH more to do with Power needs.

it would be much better to Not "feel" the needs and to actually have a grasp on what they are.

Free Energy | searching for free energy and discussing free energy

Re: High Efficiency LED for Joule Thief, etc.
« Reply #6 on: August 14, 2015, 03:29:15 PM »
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Offline MarkE

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #7 on: August 14, 2015, 04:19:07 PM »
Typical comments from Big business attempts / failures  in this area have MUCH more to do with Power needs.

it would be much better to Not "feel" the needs and to actually have a grasp on what they are.
Is that too much or too little coffee talking this morning? 

Water requirements translate to energy needs.  Transportation translates to energy needs.  The fruit and vegetable basket for the USA is in a severe drought right now.  Dropping water needs for vegetables by 90% means dropping a lot of the energy requirements.  20% of California's electricity is used moving water through the state.  80% of that water goes to agriculture.  While it would be nice to know the specific power in the lighting the video suggests that it is not that great.

Online ramset

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #8 on: August 14, 2015, 04:40:31 PM »
Probably need a bit more Coffee  :o

  However...
  for clarity Mark E ,
You want me to get a feel for the input power by looking at the light ?

Did I just read that ??? what Forum am I at ????

it says 3 watts on the box !!
------------

Having done some investigations already , the true costs to the facility are more my Concern ATM , not so much transportation infrastructure and similar costs. Water  as outlined in the Link can be diminished to 5% or less of open field farming [so it is not a real cost to the growing facility ]

  As I have already stated the reasons given for "failure" of big business in  these big indoor growing ventures have been underestimating the energy costs to grow healthy crops , NOT trucking and water costs !


I had read from one blogger in China a reference to 30 KW for their PINK LED farm,  however he did not give more specifics except to say that he and his ":partners" in China had increased food export from their indoor Vertical Farm by 1000% in the last four years.
any info which can be provided here would be greatly appreciated.[these things are rapidly becoming trade secrets in some venues]

respectfully
Chet K

« Last Edit: August 14, 2015, 06:43:04 PM by ramset »

Offline MarkE

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #9 on: August 14, 2015, 08:18:37 PM »
Probably need a bit more Coffee  :o

  However...
  for clarity Mark E ,
You want me to get a feel for the input power by looking at the light ?

Did I just read that ??? what Forum am I at ????

it says 3 watts on the box !!
------------

Having done some investigations already , the true costs to the facility are more my Concern ATM , not so much transportation infrastructure and similar costs. Water  as outlined in the Link can be diminished to 5% or less of open field farming [so it is not a real cost to the growing facility ]

  As I have already stated the reasons given for "failure" of big business in  these big indoor growing ventures have been underestimating the energy costs to grow healthy crops , NOT trucking and water costs !


I had read from one blogger in China a reference to 30 KW for their PINK LED farm,  however he did not give more specifics except to say that he and his ":partners" in China had increased food export from their indoor Vertical Farm by 1000% in the last four years.
any info which can be provided here would be greatly appreciated.[these things are rapidly becoming trade secrets in some venues]

respectfully
Chet K
If you want hard numbers you will have to dig.  Begin with PPFD.

Free Energy | searching for free energy and discussing free energy

Re: High Efficiency LED for Joule Thief, etc.
« Reply #9 on: August 14, 2015, 08:18:37 PM »
Sponsored links:




Online ramset

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #10 on: August 14, 2015, 08:31:26 PM »
Soo
would you care to guess ?? [to the trained yet uncalibrated eye ]

watts per square foot of growing space [for lettuce]
lets see how close you get .

since I will be looking into this with the manufacturer , [Phillips and others]

Offline MarkE

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #11 on: August 14, 2015, 08:47:26 PM »
Soo
would you care to guess ?? [to the trained yet uncalibrated eye ]

watts per square foot of growing space [for lettuce]
lets see how close you get .

since I will be looking into this with the manufacturer , [Phillips and others]
A quick survey suggests an upper limit of 600 PPFD for lettuce.  To translate that to Watts you have to go through the efficiency of a particular lamp design.


Offline TinselKoala

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #12 on: August 18, 2015, 06:48:51 AM »
I'm presently testing a MXA8-PW30-0000 LED (see data sheet attached below.)
These have a color temperature of 3000K, rather than the 5700K unit
shown in the videos I linked up above.

At 80 mA, just over 3V, straight DC, it's like a tiny sun it is so bright. It leaves purple spot
afterimages, I can't look directly at it, so I have it pointed away, down at the floor. 

It does get perceptibly warm but not enough to need a formal heatsink yet. In a little while
I'll run it up to 100 mA and see if it lasts.

It runs my "perpendupetulum" light powered pendulum quite well, from a foot away from the PV cell.



Offline MarkE

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #13 on: August 18, 2015, 12:52:46 PM »
I'm presently testing a MXA8-PW30-0000 LED (see data sheet attached below.)
These have a color temperature of 3000K, rather than the 5700K unit
shown in the videos I linked up above.

At 80 mA, just over 3V, straight DC, it's like a tiny sun it is so bright. It leaves purple spot
afterimages, I can't look directly at it, so I have it pointed away, down at the floor. 

It does get perceptibly warm but not enough to need a formal heatsink yet. In a little while
I'll run it up to 100 mA and see if it lasts.

It runs my "perpendupetulum" light powered pendulum quite well, from a foot away from the PV cell.
Those LEDs are a real treat.


Offline TinselKoala

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Re: High Efficiency LED for Joule Thief, etc.
« Reply #14 on: August 19, 2015, 09:10:48 AM »
Here's a surface brightness comparison. The A19 LED bulb in the desklamp is a "60W" equivalent, rated 800 lumens, soft white 2700K "EarthBulb" brand. The test LED is a MXA8-PW40-0000 high-efficiency LED with a 4000K color temperature, running at 95 mA straight DC, held right up in contact with the A19 bulb. The camera image is taken at 1/500 second, f/32, ISO1600, with my Canon Rebel Xti DSLR. To the naked eye the tiny LED is much brighter than the equivalent surface area of the A19 bulb, and the camera tells me the LED is actually overexposed in this image.


Free Energy | searching for free energy and discussing free energy

Re: High Efficiency LED for Joule Thief, etc.
« Reply #14 on: August 19, 2015, 09:10:48 AM »

 

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