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Author Topic: Joule Thief  (Read 4300274 times)

Offline MileHigh

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Re: Joule Thief
« Reply #16890 on: February 21, 2016, 07:23:38 PM »
Yes I saw the spikes and it's highly likely that they are coming from all sorts of possible external sources, and not the corroding magnesium.

Free Energy | searching for free energy and discussing free energy

Re: Joule Thief
« Reply #16890 on: February 21, 2016, 07:23:38 PM »

Offline Pirate88179

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Re: Joule Thief
« Reply #16891 on: February 21, 2016, 08:09:44 PM »
Yes I saw the spikes and it's highly likely that they are coming from all sorts of possible external sources, and not the corroding magnesium.

Well, I still like that I can light up all that I have been able to light up for free.  There was no 60 Hz component that I could detect but, I guess it does not really matter where the energy is coming from as long as it is usable right?

Also, my magnesium block still appears to be alive and well after about 5 years...although, to be fair, I have not run lights all the time from it...usually just around Christmas and special occasions.  I am sure that it will give out one day.  The carbon rods are just fine, as would be expected.

Bill

Free Energy | searching for free energy and discussing free energy


Offline MileHigh

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Re: Joule Thief
« Reply #16892 on: February 21, 2016, 08:27:48 PM »
If you read Revolution Green a company has what resembles an LED-based camping-style lantern that uses a magnesium cylinder and salt water to power the LEDs.  You get something like 150 hours (if I remember) from the cylinder.

Offline Pirate88179

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Re: Joule Thief
« Reply #16893 on: February 21, 2016, 08:43:55 PM »
Yes, I remember reading about that.  I believe Mark D. also posted a link to that story over here somewhere.

Bill


Offline Pirate88179

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Re: Joule Thief
« Reply #16894 on: March 01, 2016, 08:40:02 PM »
I still want to know why, when I "tuned" my simple JT circuits using a vr on the base that I could go past the sweet spot and would have to back up?


In other words, if I were just lowering the resistance, then the led would get brighter the lower I went...right?  So, why would the led get brighter and brighter and then start to get dimmer and dimmer and you had to tune back to hit the sweet spot?


This is going back about 8 years but I believe I replaced the 1k base resistor with a 5k vr.  You could tune it to get the best lighting and then, measure the vr and replace with that value resistor which is what I used to do.  But then, as has been discussed, the circuit would drift out of tune as the battery voltage lowered so I ended up just leaving the vrs in place most of the time.


Bill

Free Energy | searching for free energy and discussing free energy

Re: Joule Thief
« Reply #16894 on: March 01, 2016, 08:40:02 PM »
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Offline SeaMonkey

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Re: Joule Thief
« Reply #16895 on: March 01, 2016, 09:53:56 PM »
Excellent question Pirate.  It all has to do with the Current Gain
of the transistor and the region of saturation.

As base drive current is increased by decreasing the resistance
of the base feed resistor the transistor becomes more efficient
as a switching device as it approaches saturation.

Continuing to decrease the resistance will reach a point where
the base drive pulse amplitude is sufficient to drive the transistor
into saturation efficiently without excessive losses.

Reducing the resistance even further beyond that point will cause
the base drive pulse amplitude to increase base current even more
but with excessive losses.  The increased base drive is counter
productive as it is more than is needed to achieve saturation and
represents wasted power.  As a consequence the output of the
circuit (LED brilliance) will decrease indicating excessive power loss
and reduced efficiency.

The "sweet spot" is where the base drive amplitude is just sufficient
to put the transistor into saturation for minimum losses.

Offline Pirate88179

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Re: Joule Thief
« Reply #16896 on: March 02, 2016, 01:28:56 AM »
Excellent question Pirate.  It all has to do with the Current Gain
of the transistor and the region of saturation.

As base drive current is increased by decreasing the resistance
of the base feed resistor the transistor becomes more efficient
as a switching device as it approaches saturation.

Continuing to decrease the resistance will reach a point where
the base drive pulse amplitude is sufficient to drive the transistor
into saturation efficiently without excessive losses.

Reducing the resistance even further beyond that point will cause
the base drive pulse amplitude to increase base current even more
but with excessive losses.  The increased base drive is counter
productive as it is more than is needed to achieve saturation and
represents wasted power.  As a consequence the output of the
circuit (LED brilliance) will decrease indicating excessive power loss
and reduced efficiency.

The "sweet spot" is where the base drive amplitude is just sufficient
to put the transistor into saturation for minimum losses.

SeaMonkey:

Thank you very much for your detailed answer.  That makes a lot of sense to me.

Bill

Free Energy | searching for free energy and discussing free energy

Re: Joule Thief
« Reply #16896 on: March 02, 2016, 01:28:56 AM »
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