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Solid States Devices => Joule Thief => Topic started by: Jeg on April 15, 2013, 08:27:38 AM

Title: Is that a joule thief?
Post by: Jeg on April 15, 2013, 08:27:38 AM
Hi
I would like to ask if the classic topology of transistor with a feedback coil, is actually a joule thief. What it makes me confused is that the feedback uses less turns than collector's coil, the opposite of the classic Joule Ringer topology.. see below
 tnks
Title: Re: Is that a joule thief?
Post by: Groundloop on April 15, 2013, 08:21:59 PM
Hi Jeg,

I do not know if there is a definition of a Joule Thief circuit, but
when people say Joule Thief, I always think about a small power oscillator
that can run down a AA size battery fully, and give light to one or many ultra bright LED.

The circuit you posted is a power oscillator capable of generating many Watts of
power to the output. You can get whatever voltage output from the circuit you want,
depending on the turn ratio of the input power coil and output coil.

Thanks for posting and welcome to the forum. :-)

GL.
Title: Re: Is that a joule thief?
Post by: Jeg on April 17, 2013, 12:51:19 PM
Thank you Groundloop, nice to meet you all here. :)
Title: Re: Is that a joule thief?
Post by: Dave45 on April 18, 2013, 02:23:28 PM
I was just studying the circuit thinking we make transformers that put out high voltage or high amperage why not do both  ;)

 
Title: Re: Is that a joule thief?
Post by: Dave45 on April 18, 2013, 02:35:38 PM
I would think the primary's would need to be the same weight, the same with the secondary's.

The circuit would be lopsided but the mosfet's are triggered from the bemf of the coils so it should work.

 :-\
Title: Re: Is that a joule thief?
Post by: Groundloop on April 18, 2013, 02:46:23 PM
I would think the primary's would need to be the same weight, the same with the secondary's.

The circuit would be lopsided but the mosfet's are triggered from the bemf of the coils so it should work.

 :-\

Hi Dave,

You need to use wire thickness on the input that can handle the amperage from the switching circuit.
Same goes for the output, your wire must be thick enough to handle the current usage of the load.

You will not get any energy amplification by using two different wire thickness. The only thing that will
happen is that the thinner wire will go warm if there is too much current through the wire.

But I understand what you are thinking. Is there any way we can "combine" a high voltage/low current with a
low voltage/high current into the same coil. We can't mix that direct but maybe there is another way to do it?

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 18, 2013, 03:05:14 PM
The attached circuit is the closest thing to do what I described in the above post. I call it the Figure-8 circuit.
This circuit will give you a high output voltage with a relative few turns of wire. I have tested the circuit to
light up normal light bulbs and also CFL's etc.

The Figure-8 circuit is a bit tricky to get into tune. The easiest way to do it is to make too many
turns on the center coupling coil. Then connect a constant load to the output coil, e.g. a 220 Volt
15 to 25 Watt light bulb. Then you must check that the center coil is connected the correct way.
The wrong way will give very poor output. Last, you must remove one turn at the time and measure
the output voltage. At the correct number of turns, the output voltage will shoot up, just as in a tuned
LC coil/capacitor tank circuit. Be careful and do not run the circuit close to Hi-Fi, TVs,
computers etc. All metal and all wires regardless of length will get an current generated. Be careful when
running the Figure-8 circuit. The output coil can generate up to 30 Watt (depending on the core size and coils)
of power at many hundred volts. It can harm or kill, so do not touch the circuit when running.

The transistor (high voltage power NPN) you choose to use must be of a high voltage type. 1000 to 1500 Volt
or better. The best result I had was with the BUX80. But this transistor is hard to get hold on. The transistor must
also be mounted onto a heat sink. It is possible to parallel more than one transistor.
The variable resistor must be at least of a 3,5 Watt type. The transistor needs a lot of bias current.

I have made very small versions of the Figure-8 circuit. One was with two tiny Toroid cores driven from a 9 volt
battery. The output coil generated 100 Volt pulsed DC. This was enough to light up a small guttered CFL. :-)

Some theory about the Figure-8 circuit:

The input part is a normal oscillator with a feed-back coil and DC bias to the transistor. At each switch on pulse
in the oscillator there will be generated a positive high voltage spike in the coil. This high voltage spike is feed through
a diode to the middle coupling coil sharing the two Toroid cores. The pulse is then "recycled" back to the positive, thus
we do not waste the voltage spike, making the oscillator COP even higher. The side effect of doing this is that the
transistor has "short circuited" the middle coupling coil at the same time as the input pulse is present in the coil. Shorting
the coupling coil does not require any energy usage at all. We get that for free. This will then transfer a current and voltage
to the second (right) core and we get a output. But, the high voltage spike is overlapped the normal transformer coupling
so that we get an voltage amplification of the output. The voltage amplification is much higher than a normal transformer
ratio. (N1:N2). This means we need just a few turns of wire in the output coil to get a high voltage.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 18, 2013, 03:17:43 PM
If you want to play with a simple and easy to make Joule Thief, then the attached circuit
is somewhat special and fun. The circuit will give you a "night light" in a ultra bright white
light emitting diode(LED) for weeks from a drained 9 volt battery. The coils in my circuit
was from a guttered CFL circuit board. The circuit uses two separate coils and the coils
needs to be spaced apart a centimeter or so. You can use a 2N2222A in the circuit instead
of the MPSA06.

GL.
Title: Re: Is that a joule thief?
Post by: e2matrix on April 18, 2013, 10:45:56 PM
Hi Groundloop,  Thanks for sharing that figure 8 circuit.  I think I've got everything to build it except the diode.  I've got a C5778 transistor with 1600v 15A ratings and it's a high speed NPN that I think will work fine to replace the NTE2354 and a 225 watt rheostat should handle the variable resistor ;) 
While looking in a folder of saved info from you I found the diagram below from you from 2011 but I can't seem to find any message thread tied to it.  Do you have any idea where I might find more about it?   
Title: Re: Is that a joule thief?
Post by: Groundloop on April 19, 2013, 07:00:42 AM
Hi Groundloop,  Thanks for sharing that figure 8 circuit.  I think I've got everything to build it except the diode.  I've got a C5778 transistor with 1600v 15A ratings and it's a high speed NPN that I think will work fine to replace the NTE2354 and a 225 watt rheostat should handle the variable resistor ;) 
While looking in a folder of saved info from you I found the diagram below from you from 2011 but I can't seem to find any message thread tied to it.  Do you have any idea where I might find more about it?

e2matrix,

Yes, the transistor you list will probably do the job fine. Same goes for your rheostat.

The drawing you posted here was posted in the OUR forum a couple of years ago.
I did delete by bench at OUR due to lack of interest. The above drawing was an idea
only and I have not tried it. But the idea seems good. So if you have one Ferrite toroid
and one Metglas toroid of the approx. same size, then maybe it will work. I don't know.

My test was with two Ferrite cores as shown in my first drawing. The diode is sometimes
called a P600. It is a 1000 Volt 10 Ampere diode. You can use another diode as long as
the diode can handle high voltage and some few ampere pulses. If you want to test this
setup then build the oscillator part first. If the oscillator does not run, then reverse the
trigger coil wires. Then add the middle coil and output coil. Put a load on the output coil,
a 230 VAC 25 Watt light bulb will do fine. Then connect the middle coil. The middle coil
must be reversed if the output is low. Also the middle coil must be tuned to the frequency
of the oscillator. Too many numbers of turns or too few number of turns will give poor output.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 20, 2013, 04:58:12 PM
Hi Groundloop,  Thanks for sharing that figure 8 circuit.  I think I've got everything to build it except the diode.  I've got a C5778 transistor with 1600v 15A ratings and it's a high speed NPN that I think will work fine to replace the NTE2354 and a 225 watt rheostat should handle the variable resistor ;) 
While looking in a folder of saved info from you I found the diagram below from you from 2011 but I can't seem to find any message thread tied to it.  Do you have any idea where I might find more about it?

e2matrix,

I finally got time to download and study the data sheet for your 2SC5778 and you can NOT use that
transistor in the Figure-8 circuit. The reason is that the 2N5778 has an internal diode over the collector
emitter wires. The transistor also have a internal resistor between base and emitter. You need to find
a high voltage power NPN transistor that does not have any internal "extra" components.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 21, 2013, 06:43:46 PM
Today I did a test with two depleted 8,4 Volt 120mA rechargeable Ni-Cad batteries.
I did connect the two batteries in series and the start voltage was almost 9 volt.
(Less than 4,5 Volt in each battery, totally drained.) I have connected the batteries
to the JT posted above. I have found that it is almost impossible to fully drain a
rechargeable Ni-Cad battery to zero volt. It will always gain some small value after
a prolonged short circuit. So I assume that rechargeable Ni-Cad batteries has the
same "self charge effect" as electrolytic capacitors have. I know that my JT will run
fine down to approx. 2 Volt. So it will be funny to see if the "self charge effect" in the
batteries will keep the LED lit for some prolonged time. Expriment started 21.04.2013
at 1500 local time. Measured voltage was 8,9 Volt. Now I must let the JT run and see
when (or if) the LED will go totally dim.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 22, 2013, 04:00:04 PM
Now (22.04.2013 1600) the JT circuit has run over 24 hours. The voltage in the two series
batteries has dropped to 3,72 Volt, but that was expected. The LED is still giving out
a good "night light" level. Both batteries is very close to the "self charge" level where
the "self charge" should kick in. I know from earlier tests that it is almost impossible
to fully drain a battery to zero volt. The battery always "want" to have some small
level of charge. So I will let the circuit run and see what happen.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 23, 2013, 05:46:44 AM
Now we are into day 3 of the run down test. The combined battery voltage is now 2,87 Volt.
The LED still has enough light to be useful for night lighting. The frequency of the oscillator
has been constant at approx. 479KHz during the run and has not changed much since the
start of the run. A 9 Volt rechargeable battery (Ni-Cad is actually 8,4 Volt) has 6 cells inside
connected in series. Since I have connected two such batteries in series then we have 12 single
cells in series. So each battery cell is now at 0,2391 Volt. Remember that we started the run
with two drained batteries. It is my theory that it is impossible to fully drain a battery to
zero Volt because of the battery "self charge effect". So by theory at some point in the
discharge curve of the battery we should see that the voltage stops dropping. Where this
voltage point is at is unknown right now so I will keep the circuit running until there is no
more useful light in the LED. To be continued...............................

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 23, 2013, 03:09:08 PM
Now (23.04.2013 1500) the battery voltage is 2,83 Volt.
LED still providing enough light to be a "night light".
Only 0,04 Volt battery voltage drop in 9 hours.

GL.
Title: Re: Is that a joule thief?
Post by: e2matrix on April 23, 2013, 07:01:31 PM
e2matrix,

I finally got time to download and study the data sheet for your 2SC5778 and you can NOT use that
transistor in the Figure-8 circuit. The reason is that the 2N5778 has an internal diode over the collector
emitter wires. The transistor also have a internal resistor between base and emitter. You need to find
a high voltage power NPN transistor that does not have any internal "extra" components.

GL.


Thanks Groundloop.   I do see that extra stuff now in my datasheet.  This transistor is working now in a battery charger circuit posted by member rfnreynders on Laserhacker.com and on energeticforum.com and seems to be one of the few I've tried works good in that circuit for that 'big spike' desired for desulfating.    I've got a 2SC2555 that looks like it might work for the figure 8 circuit but my datasheet doesn't show any internal configuration -- so I'm assuming it doesn't have any extra 'stuff'.   
Title: Re: Is that a joule thief?
Post by: Groundloop on April 23, 2013, 09:14:38 PM

Thanks Groundloop.   I do see that extra stuff now in my datasheet.  This transistor is working now in a battery charger circuit posted by member rfnreynders on Laserhacker.com and on energeticforum.com and seems to be one of the few I've tried works good in that circuit for that 'big spike' desired for desulfating.    I've got a 2SC2555 that looks like it might work for the figure 8 circuit but my datasheet doesn't show any internal configuration -- so I'm assuming it doesn't have any extra 'stuff'.

e2matrix,

I did download the data sheet for the 2SC2555 and the transistor is OK to use in the Figure-8 circuit.

( My JT battery voltage is now [23.04.2013 2100] down to 2,81 Volt. That is a drop of 0,02 Volt in 6 hours. )

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 24, 2013, 06:48:57 AM
My JT battery voltage is now [24.04.2013 0645] down to 2,79 Volt. That is a drop of 0,02 Volt in approx. 10 hours.
LED still bright enough to be used as a night light. Oscillator frequency at 465KHz.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 24, 2013, 04:45:05 PM
My JT battery voltage is now [24.04.2013 1645] down to 2,77 Volt. That is a drop
of 0,02 Volt in 10 hours. LED still bright enough to be used as a night light.

GL.
Title: Re: Is that a joule thief?
Post by: e2matrix on April 24, 2013, 05:47:09 PM
Thanks again Groundloop.   Sounds like you've got a finely tuned JT there.   Thumbsup smiley here  (hint hint Stephan)
Title: Re: Is that a joule thief?
Post by: Groundloop on April 24, 2013, 06:46:03 PM
Thanks again Groundloop.   Sounds like you've got a finely tuned JT there.   Thumbsup smiley here  (hint hint Stephan)

e2matrix,

This JT circuit is inspired by Dr. Stiflers work on the Spatial Energy Coherence (SEC) Exciter circuit.
Thanks goes to Dr. Stifler. I have two tuning components in my version of the circuit. The frequency
of the oscillator is set by C1 and L2 at the base of the circuit. And the oscillator frequency is very
constant over a wide range of input voltages.  R1 (1M Ohm) provide the voltage bias to get the
oscillator going. The L2 coil is flat on the circuit board and the L1 coil is mounted vertically. This means
that there is just a small L1 to L2 coupling. The end result is a oscillator that can be run on a wide
range of input voltages with a relative constant light output in the LED. The LED is also mounted
directly over the L1 coil so that the current through the LED is channeled back to the positive rail.
This will give a oscillator that uses very little current from the input. The LED I'm using is a ultra bright
blue 10mm diameter LED. The L1 and L2 coil can be found on the PCB of CFL lamps. All in all a funny
circuit to play with. I highly recommend people to study Dr. Stiflers work on the Spatial Energy Coherence
(SEC) Exciter circuit.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 25, 2013, 06:22:13 AM
My JT battery voltage is now [25.04.2013 0620] down to 2,66 Volt. That is a drop
of 0,11 Volt in almost 14 hours. LED is no longer bright enough to be used as a night light.
Seems that the batteries is now close to almost no charge left. Will keep the circuit running
until LED goes fully dim to see how low voltage this circuit can run on. Oscillator frequency
is now at 467KHz.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 25, 2013, 03:46:02 PM
My JT battery voltage is now [25.04.2013 1545] down to 2,61 Volt. That is a drop
of 0,05 Volt in approx. 9 hours. LED is very dim now, barley any light, but still visible.
Oscillator frequency is now 471KHz. Amazing stable during the various input voltages.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 26, 2013, 07:12:03 AM
My JT battery voltage is now [26.04.2013 0645] down to 2,55 Volt. That is a drop
of 0,06 Volt in 15 hours. LED light is still visible, but very dim. Oscillator at 474KHz.

GL.
Title: Re: Is that a joule thief?
Post by: TinselKoala on April 26, 2013, 01:20:22 PM
Hi GL very nice work as usual.....

I love your spectrum analyzer display. What instrument is that from?  My lab is sorely lacking in that regard; I have been trying to obtain a spectrum analyzer plugin for my HP180a for some time now but just can't afford it.

I'm a little scared of your copyright notice.... May I please have permission to copy that schematic image of your Oscillator to my hard drive, for my personal use only?    ;)

When it's finally too dim to see, I wonder what would happen if you warmed the batteries gently.....

Cheers, keep up the good work...
--TK
Title: Re: Is that a joule thief?
Post by: Groundloop on April 26, 2013, 02:00:19 PM
Hi GL very nice work as usual.....

I love your spectrum analyzer display. What instrument is that from?  My lab is sorely lacking in that regard; I have been trying to obtain a spectrum analyzer plugin for my HP180a for some time now but just can't afford it.

I'm a little scared of your copyright notice.... May I please have permission to copy that schematic image of your Oscillator to my hard drive, for my personal use only?    ;)

When it's finally too dim to see, I wonder what would happen if you warmed the batteries gently.....

Cheers, keep up the good work...
--TK

TK,

Yes, you can copy my circuit drawing to your hard drive. :-)

The spectrum analyzer is from my Icom PCR-1000 receiver.
(Icom has also made a new model called PCR2500).
The program I use is freeware and is called Talk PCR.
See here: http://www.m0kgk.co.uk/pcr1000.php

I will try to warm the battery when the LED goes out. :-)

GL.

Title: Re: Is that a joule thief?
Post by: Groundloop on April 26, 2013, 03:45:02 PM
My JT battery voltage is now [26.04.2013 1545] down to 2,51 Volt. That is a drop
of 0,04 Volt in 9 hours. LED light is still visible, but very low.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 26, 2013, 09:49:10 PM
My JT battery voltage is now [26.04.2013 2145] at 2,51 Volt. That is a drop
of 0,00 Volt in 6 hours. LED light is still visible, but very very low. The oscillator is
still running happily at 477KHz. Question now is, will the oscillator keep running
on the "battery self charge effect" now that each cell in the batteries is depleted
down to  0,2092 Volt? Time will tell........................

GL.
Title: Re: Is that a joule thief?
Post by: forest on April 26, 2013, 10:29:14 PM
Try how long does it run from a farad capacitor or smaller....  :D
Title: Re: Is that a joule thief?
Post by: Groundloop on April 26, 2013, 11:01:16 PM
Try how long does it run from a farad capacitor or smaller....  :D

forest,

Yes, I will try that also. But first I want to see how long the oscillator will keep
running on the two depleted batteries. It might take some weeks, it may take
longer. I think this is an important test because I have never been able to
fully drain a battery to zero volt by shorting the battery.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 27, 2013, 09:45:50 AM
My JT battery voltage is now [27.04.2013 0945] at 2,48 Volt. That is a drop
of 0,03 Volt in 12 hours. LED light is still visible, but very very low. Osc. at 479KHz.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 27, 2013, 10:25:49 PM
I did a change today. I did add a Neo magnet close to the L2 coil. This did increase
the circuit current use from the batteries. It also made the LED brighter because
of this. The batteries voltage did drop to 1,720 Volt (1600 local time.) I did this to
speed up the battery draw down test. I'm not testing the circuit, I'm testing if a
battery can be fully drained to zero volt or if the "battery self charge effect" will
kick in and keep the voltage at a low level.

My JT battery voltage is now [27.04.2013 2200] at 1,568 Volt. This is a drop of
0,152 Volt during 6 hours. The frequency of the oscillator is now 745KHz with a
lot of harmonics up in the frequency band. But I also can hear an audio tone of
approx. 1KHz modulated from the oscillator, so I think that what I see on the
spectrum analyzer is just over-harmonics of the real oscillator frequency.

GL.
Title: Re: Is that a joule thief?
Post by: Jeg on April 27, 2013, 10:53:19 PM
Dear all
I tried the circuit i posted on the first page, with a 3055 and 24V. Four turns for the feedback, and the internal coil of the flyback as primary. Well, it draws around 4 Amber maximum, and produces around 2KV. What i would like to ask, is why it changes the frequency of resonance according with the length of the spark. I mean, when the output electrodes are very close, the frequency is about 5KHz, and when they are in distance, it goes to 17KHz! Does anyone know why this happen?
Title: Re: Is that a joule thief?
Post by: Groundloop on April 27, 2013, 10:59:04 PM
Dear all
I tried the circuit i posted on the first page, with a 3055 and 24V. Four turns for the feedback, and the internal coil of the flyback as primary. Well, it draws around 4 Amber maximum, and produces around 2KV. What i would like to ask, is why it changes the frequency of resonance according with the length of the spark. I mean, when the output electrodes are very close, the frequency is about 5KHz, and when they are in distance, it goes to 17KHz! Does anyone know why this happen?

Hi Jeg,

The oscillator frequency will change based on how much you load the output.
Higher load will give lower frequency. What are you going to use your circuit for?

GL.
Title: Re: Is that a joule thief?
Post by: Jeg on April 27, 2013, 11:29:37 PM
I will use this output to fire through a rotor spark gap, to a tesla coil. I was just hopping to have this output with a JT for lower pwr consumption..
Title: Re: Is that a joule thief?
Post by: Jeg on April 28, 2013, 10:20:36 AM
Hi Jeg,

The oscillator frequency will change based on how much you load the output.

GL.

Hi GL
I'd like to ask you if there is any way with this setup, to avoid this freq. changing. I am thinking to add a hand made smoothing capacitor of 0,5nF to smooth a 10KHz resonance. Flyback is already have the internal diode, so i calculated the capacitor with 10mA output, 20KV, 10% ripple, and 0,1ms between charging peaks. Do you think is a good idea first to fix the sparking gaps around the rotor and then to re-calculate the cap?

tnks in advance
Title: Re: Is that a joule thief?
Post by: Groundloop on April 28, 2013, 10:55:22 AM
Hi GL
I'd like to ask you if there is any way with this setup, to avoid this freq. changing. I am thinking to add a hand made smoothing capacitor of 35pf to smooth a 10KHz resonance. Flyback is already have the internal diode, so i calculated the capacitor with 10mA output, 20KV, 10% ripple, and 0,1ms between charging peaks. Do you think is a good idea first to fix the sparking gaps around the rotor and then to re-calculate the cap?

tnks in advance

Hi Jeg,

I think that the only way to avoid a frequency change with load is to use some sort of a feed back
from the output that control your oscillator. Or you can also use a fixed frequency oscillator that
control a switch connected to your fly-back transformer. If you look at a typical switch mode power
supply, then you will see that the SMPS uses a circuit to determine the output voltage and then
couple back to the input switch via opto-couplers to keep the output voltage at a constant level
during various loads. So I think your best option is to use a 4047N oscillator to keep your switch
at a constant frequency. One circuit that uses a 4047N IC as a constant frequency oscillator is
attached this post. The frequency is set by the 220K pot and the 100nF capacitor. These values
can be changed to suit your needs. My build of this circuit had a little more electronics on the board
than shown in the attached circuit drawing. Hope this help you in your quest.....

GL.
Title: Re: Is that a joule thief?
Post by: Jeg on April 28, 2013, 11:16:44 AM
Thanks a lot GL. Nice driver schematic. The reason i don't want to use it in this hobie project is because i 'd like to explore auto resonance and its effects. What if i add before the charging capacitor the following coil with the de-q-ing diode? Will it make it more steady in frequency?
By the way. Is it possible to show me the equation that calculates this change due to load?

tnks

http://www.richieburnett.co.uk/dcreschg.html
Title: Re: Is that a joule thief?
Post by: Jeg on April 28, 2013, 11:28:22 AM
I think i got it. The gap introduces a capacitance which varies with  electrode distance, so as the frequency. After the charging resonant circuit, this capacitance doesn't affect anymore the secondary coil, so frequency will be steady (as far as i think that i understand! :D)
Title: Re: Is that a joule thief?
Post by: Groundloop on April 28, 2013, 11:45:12 AM
Thanks a lot GL. Nice driver schematic. The reason i don't want to use it in this hobie project is because i 'd like to explore auto resonance and its effects. What if i add before the charging capacitor the following coil with the de-q-ing diode? Will it make it more steady in frequency?
By the way. Is it possible to show me the equation that calculates this change due to load?

tnks

http://www.richieburnett.co.uk/dcreschg.html

Jeg,

I'm more a builder type than a mathematical type, so I do not know much about the formula you ask about. :-)
You will need to look at the net or maybe some of the math experts on this forum can chip in with an explanation?

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 28, 2013, 11:52:54 AM
I think i got it. The gap introduces a capacitance which varies with  electrode distance, so as the frequency. After the charging resonant circuit, this capacitance doesn't affect anymore the secondary coil, so frequency will be steady (as far as i think that i understand! :D)

Jeg,

You said in a earlier post that you will use a rotary spark gap. I would guess that the RPM of
the rotary spark gap will set the switching frequency to your Tesla coil primary? And if you
have a constant power available into your rotary spark gap, then the power going into
your primary Tesla coil will be lower as the RPM goes up. This because your primary capacitor
will be charged less by your high voltage power supply for each firing at your spark gap. But I
think that the frequency will be set by the RPM of your rotary spark gap.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 28, 2013, 07:00:02 PM
My JT battery voltage is now [28.04.2013 1900] at 1,537 Volt. This is a drop of
0,031 Volt during 21 hours. The LED is light dimly.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 29, 2013, 04:10:08 AM
My JT battery voltage is now [29.04.2013 0400] at 1,508 Volt. This is a drop of
0,029 Volt during 9 hours. The LED is light dimly.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 29, 2013, 04:05:11 PM
My JT battery voltage is now [29.04.2013 1600] at 1,489 Volt. This is a drop of
0,019 Volt during 12 hours. The LED is light dimly.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 29, 2013, 09:35:11 PM
My JT battery voltage is now [29.04.2013 2130] at 1,304 Volt. This is a drop of
0,185 Volt during 5:30 hours. The LED is light very dimly.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 30, 2013, 06:24:54 AM
My JT battery voltage is now [30.04.2013 0630] at 1,147 Volt. This is a drop of
0,157 Volt during 9 hours. The LED is light very dimly.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on April 30, 2013, 05:36:30 PM
My JT battery voltage is now [30.04.2013 1730] at 1,032 Volt. This is a drop of
0,115 Volt during 11 hours. The LED is light very very dimly. So, how long until
we reach zero Volt on the batteries?

GL.
Title: Re: Is that a joule thief?
Post by: TinselKoala on April 30, 2013, 05:38:19 PM
I dunno, I'm too lazy to plot the curve and project it out. But won't your JT stop oscillating at around 0.4 V or so?
Title: Re: Is that a joule thief?
Post by: Groundloop on April 30, 2013, 07:09:15 PM
I dunno, I'm too lazy to plot the curve and project it out. But won't your JT stop oscillating at around 0.4 V or so?

TK,

A typical JT can't start to oscillate if the base voltage bias is below the level needed by the transistor, but
once started, the oscillator will happily oscillate down to 0,1 Volt because the pulses in the trigger coil
is higher than the approx. 0,6 Volt base voltage needed to trigger the transistor. That said, my LED brightness
is now down to almost nothing. So I think I will stop the drain down test soon.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on May 01, 2013, 05:44:36 AM
My JT battery voltage is now [01.05.2013 0530] at 0,970 Volt. This is a drop of
0,062 Volt during 12 hours. The LED is light very very dimly, almost off.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on May 01, 2013, 04:30:31 PM
My JT battery voltage is now [01.05.2013 1630] at 0,949 Volt. This is a drop of
0,021 Volt during 11 hours. The LED is light very very dim, almost off.

GL.
Title: Re: Is that a joule thief?
Post by: TinselKoala on May 01, 2013, 05:47:30 PM
Have you considered making a light-level sensing instrument? I am impressed with the performance of the NTE3037 phototransistor; it would be fairly easy to make a light output meter with this as the sensor and a regulated supply from a 78L05 mini-regulator.
There are also some complete lightlevel sensors-on-chip like the TSL235R that would make a neat addition to a JT workbench setup.
Title: Re: Is that a joule thief?
Post by: Groundloop on May 01, 2013, 07:30:40 PM
Have you considered making a light-level sensing instrument? I am impressed with the performance of the NTE3037 phototransistor; it would be fairly easy to make a light output meter with this as the sensor and a regulated supply from a 78L05 mini-regulator.
There are also some complete lightlevel sensors-on-chip like the TSL235R that would make a neat addition to a JT workbench setup.

TK,

It would probably be nice to have a a light-level sensing instrument, but in this test I do not need it.

This test is to see if is it possible to fully drain a battery down to zero Volt. My theory is that this
is not possible, not even with a short. The battery will always go back to some low voltage. So my LED
is there to see if the circuit runs or not. But if I find a way to light a LED to some higher level,
using "dead" batteries, then a light meter could be used to measure the output.

Do you know any IC that can light a ultra bright LED to a reasonable light level from a very low
input voltage, say 0,1 to 0,5 Volt or so?

Added: I just found one. The LTC3108 can operate down to 20mV input. Data sheet attached.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on May 02, 2013, 10:36:15 AM
My JT battery voltage is now [02.05.2013 1030] at 0,931 Volt. This is a drop of
0,018 Volt during 18 hours. The LED is light very dim, almost off, and is flickering.

If I touch almost any parts of the circuit, then the LED goes off. Yesterday [01.05.2013 2300]
the voltage was 0,925 Volt. So the voltage has increased somewhat during the night.

GL.
Title: Re: Is that a joule thief?
Post by: conradelektro on May 02, 2013, 10:52:56 AM

Do you know any IC that can light a ultra bright LED to a reasonable light level from a very low
input voltage, say 0,1 to 0,5 Volt or so?

Added: I just found one. The LTC3108 can operate down to 20mV input. Data sheet attached.

GL.

@Groundloop: a poster named magpwr showed a circuit and the transistor 2SK170 which lights a LED dimly down to 30 mV input power, I could do it with 50 mV.

Attached you see the circuit based on this transistor.

Greetings, Conrad
Title: Re: Is that a joule thief?
Post by: Groundloop on May 02, 2013, 11:21:48 AM
@Groundloop: a poster named magpwr showed a circuit and the transistor 2SK170 which lights a LED dimly down to 30 mV input power, I could do it with 50 mV.

Attached you see the circuit based on this transistor.

Greetings, Conrad

Hi Conrad,

Thanks for posting this, I will study the data sheets for the components.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on May 02, 2013, 08:17:44 PM
My JT battery voltage is now [02.05.2013 2018] at 0,893 Volt. This is a drop of
0,038 Volt during approx. 10 hours. The LED light is steady and very dim.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on May 03, 2013, 08:21:34 AM
My JT battery voltage is now [03.05.2013 0818] at 0,888 Volt. This is a drop of
0,005 Volt during 12 hours. The LED light is flickering and very dim.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on May 03, 2013, 08:30:32 PM
My JT battery voltage is now [03.05.2013 2018] at 0,889 Volt. This is a increase of
0,001 Volt during 12 hours. The LED light is flickering and very dim.

GL.
Title: Re: Is that a joule thief?
Post by: Groundloop on May 04, 2013, 10:47:19 AM
My JT circuit did stop oscillating tonight. No light in the LED and no signal received in my spectrum analyzer.
The battery voltage today was 0,885 Volt. My next attempt to fully drain the batteries will be a J-Fet circuit
(as posted by Conrad). But first I have to find some J-Fet transistors.....................  :-)

GL.
Title: Re: Is that a joule thief?
Post by: Pirate88179 on May 05, 2013, 11:19:31 PM
GL:

Most of my regular run of the mill JT's will drain a Bat. to about .2 volts or so.  I think Gadget got some of his to go way lower.  Of course, these were not looped to try to re-claim any of the energy or anything.

Keep up the great work that you do.

Bill