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Author Topic: Is that a joule thief?  (Read 72711 times)

Groundloop

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Re: Is that a joule thief?
« Reply #30 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.

Groundloop

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Re: Is that a joule thief?
« Reply #31 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.

Jeg

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Re: Is that a joule thief?
« Reply #32 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?

Groundloop

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Re: Is that a joule thief?
« Reply #33 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.

Jeg

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Re: Is that a joule thief?
« Reply #34 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..

Jeg

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Re: Is that a joule thief?
« Reply #35 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

Groundloop

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Re: Is that a joule thief?
« Reply #36 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.

Jeg

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Re: Is that a joule thief?
« Reply #37 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

Jeg

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Re: Is that a joule thief?
« Reply #38 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)

Groundloop

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Re: Is that a joule thief?
« Reply #39 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.

Groundloop

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Re: Is that a joule thief?
« Reply #40 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.

Groundloop

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Re: Is that a joule thief?
« Reply #41 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.

Groundloop

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Re: Is that a joule thief?
« Reply #42 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.

Groundloop

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Re: Is that a joule thief?
« Reply #43 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.

Groundloop

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Re: Is that a joule thief?
« Reply #44 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.