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Author Topic: Interesting Higher Powered Joule Thief I just made - Part 2.  (Read 9586 times)

Offline Legalizeshemp420

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Interesting Higher Powered Joule Thief I just made - Part 2.
« on: October 25, 2013, 08:47:33 PM »
I am excited by what I just accomplished but I wish I had the ability to measure the current drawn from the battery and the current that was going to the LED accurately and easily.

www.youtube.com/watch?v=yECaDqKAdX8

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Offline MileHigh

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #1 on: October 25, 2013, 10:10:07 PM »
There is good news for you.  Because you have the 10 uF cap to stabilize the voltage local to the JT, you should be able to make an accurate current measurement.  Just put your multimeter between the battery and the 10 uF cap and if the digital multimeter display is stable then you will have a good measurement.

If you scope the 10 uF cap voltage before you do that you should hopefully see a near-DC voltage.  That is just confirmation that you should get a stable current measurement.

You could measure the power going through the LED.  The correct thing to measure is power in this case, because of the properties of a diode. To do it you would have to jump through some hoops though, it would be uncharted territory.  Then you compare the power in from the battery vs. the power you are pumping into the LED and get your electrical efficiency.

Did you remove that LED from a heat sink?  I advise you to put it on some kind of a heat sink, even an old CPU heat sink.  It looks powerful enough to burn itself up without one.

MileHigh


Offline Legalizeshemp420

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #2 on: October 25, 2013, 10:18:33 PM »
The heatsink is already on it else it would have burnt up for sure (the star shiny behind the LED is the aluminum heatsink).

Lets see what I measure and I know I can read a book with the LED at 6 feet easily in a dark room.

Just measured it and it read 179.5 to 180ma

Offline MileHigh

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #3 on: October 25, 2013, 10:41:27 PM »
If the back of that star-like LED substrate is flat and shiny and looks like it wants to be put on a heat sink, then you might want to consider it.  It's possible that you have not yet run it at full power with your JT experiments so be careful.  Don't forget it's a 700 mA part and I will guess that you never ran it with 700 mA DC.  That may require a heat sink.

MileHigh


Offline Legalizeshemp420

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #4 on: October 25, 2013, 10:46:46 PM »
Well, that is an interesting effect but I put a flash light bulb (12v incandescent type) in where the LED goes and it slowly revs up in brightness but never goes beyond orange.

Oh, on the LED I did run it at full voltage (power supply) and current and it barely got warm but the 5 watt version does demand a heatsink.

Free Energy | searching for free energy and discussing free energy

Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #4 on: October 25, 2013, 10:46:46 PM »
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Offline Legalizeshemp420

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #5 on: October 26, 2013, 08:14:23 AM »
I just tried it on a fresh NiMH that read 1.30V and it over ranged my meter which has a maximum of 200ma. :(  Yeah, if I had money I would have a better meter, lol.

So, I had to put it on the 10A settings and it read 0.54  Well, OMG, that is 540ma I am draining from the battery for the 700ma LED.

Interesting.

Offline Legalizeshemp420

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #6 on: October 26, 2013, 11:56:16 AM »
With the 3 watt 700ma LED in the circuit (everything is as is in the video) I get a little over 2 volts with a battery at .57 volts.  The signal is as it is in the picture.

Now if I could only get it to put out 3 or 3.5 volts at .57vdc

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #6 on: October 26, 2013, 11:56:16 AM »
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Offline TinselKoala

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #7 on: October 26, 2013, 03:51:01 PM »
1. You can use a small resistor like 1 ohm or 0.1 ohm and hook the DMM Voltmeter across the resistor and look at the voltage drop. This will give you the current by Ohm's Law.
2. You have a load (the LED) that starts out looking like an open circuit, and then as the supplied voltage rises to the LED's rated "forward voltage" the LED turns on and starts looking like a low resistance load. So the voltage you are supplying can't go much over this value, since the LED is "shorting" it out when it turns on. This is why you get higher voltage when you put LEDs in series: the JT's spikes must rise higher before the LEDs turn on and limit the voltage rise. Try running your JT with no LED load and monitor it on the scope. You should see higher voltage peaks when it's oscillating with no load.
3. You talk about "20 mA" or "700 mA" LEDs as if you expect them always to draw this current. But the current the LED draws is determined by the voltage you supply to it. The more voltage you supply, the more current the LED will draw, until the LED's limits are exceeded and it fails. Try this: hook up your straight DC power supply, your milliammeter, and your "700 mA" LED all in series, and start bringing up the voltage. You will see that the LED gets pretty darn bright well before it is drawing 700 mA. However it will not draw 700 mA until you supply it with its normal rated voltage. When you do supply it with its rated voltage and it is drawing 700 mA, then you should be at the rated light output (and you will need a heatsink, because you will be trying to dump several Watts of heat power out of that tiny LED package.)

Offline Legalizeshemp420

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #8 on: October 26, 2013, 04:26:12 PM »
1. You can use a small resistor like 1 ohm or 0.1 ohm and hook the DMM Voltmeter across the resistor and look at the voltage drop. This will give you the current by Ohm's Law.
2. You have a load (the LED) that starts out looking like an open circuit, and then as the supplied voltage rises to the LED's rated "forward voltage" the LED turns on and starts looking like a low resistance load. So the voltage you are supplying can't go much over this value, since the LED is "shorting" it out when it turns on. This is why you get higher voltage when you put LEDs in series: the JT's spikes must rise higher before the LEDs turn on and limit the voltage rise. Try running your JT with no LED load and monitor it on the scope. You should see higher voltage peaks when it's oscillating with no load.
3. You talk about "20 mA" or "700 mA" LEDs as if you expect them always to draw this current. But the current the LED draws is determined by the voltage you supply to it. The more voltage you supply, the more current the LED will draw, until the LED's limits are exceeded and it fails. Try this: hook up your straight DC power supply, your milliammeter, and your "700 mA" LED all in series, and start bringing up the voltage. You will see that the LED gets pretty darn bright well before it is drawing 700 mA. However it will not draw 700 mA until you supply it with its normal rated voltage. When you do supply it with its rated voltage and it is drawing 700 mA, then you should be at the rated light output (and you will need a heatsink, because you will be trying to dump several Watts of heat power out of that tiny LED package.)
Nope, I don't always expect them to draw that since they really aren't a resistive load and why in the simulator I can't measure anything with it.  After using a .1ohm (I do not have that value irl) and the 1 ohm in the simulator I just discounted them irl too.

Offline MileHigh

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #9 on: October 26, 2013, 05:53:49 PM »
Note that commercial LED power supplies are rated in current out, not voltage.  They are current sources.  So you always hook the LEDs in series to an LED power supply.  The higher the wattage of the power supply, the more LEDs it can drive in series.

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #9 on: October 26, 2013, 05:53:49 PM »
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Offline Legalizeshemp420

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #10 on: October 26, 2013, 10:58:05 PM »
Note that commercial LED power supplies are rated in current out, not voltage.  They are current sources.  So you always hook the LEDs in series to an LED power supply.  The higher the wattage of the power supply, the more LEDs it can drive in series.
Yep, that is very correct.

Offline Legalizeshemp420

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #11 on: October 27, 2013, 02:25:40 AM »
Using the shunt resistor of 1ohm 1% 1.23V battery with 175ma drain I read 48mV across the shunt resistor.

How can the 3W be so bright it burns to look at it with only 48ma?


Offline TinselKoala

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #12 on: October 27, 2013, 02:52:05 AM »
Where did you put your CVR in the circuit? First you say "175 mA drain", then you cite the reading of 48 mV drop across the CVR. These two numbers should agree, should they not?

Offline Legalizeshemp420

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Re: Interesting Higher Powered Joule Thief I just made - Part 2.
« Reply #13 on: October 27, 2013, 03:03:28 AM »
Where did you put your CVR in the circuit? First you say "175 mA drain", then you cite the reading of 48 mV drop across the CVR. These two numbers should agree, should they not?
They would if the Joule Thief were 100% efficient which nothing is 100% efficient.

Shunt resistor was between the cathode of the 3W LED and ground.  175ma drain on the 1.23v battery.

So, 48ma going to the LED (I find that too low to be seeing the brightness I am on a 3.25V 700ma LED) and 175ma draining the battery.  If the 48ma(mv) number is right that is 48/175 is only about 27% efficient.


 

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