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### Author Topic: Akula0083 Light No3 - Dual TL494  (Read 121752 times)

#### MarkE

• Hero Member
• Posts: 6830
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #30 on: May 11, 2014, 02:09:14 AM »
Negative resistance is a behavior, a transfer function, of a circuit that is powered externally.  Negative resistance means that as the applied voltage increases the current decreases and as the applied voltage decreases, the current increases.  In order to perform stably in oscillators, circuits that exhibit negative resistance are typically combined with limiter circuits.  Once the amplitude builds up to a certain level, the limiter diverts energy non linearly to prevent the amplitude from building to the point that the circuits saturate.  A classic example that uses the non linear resistance of an incandescent bulb is the Wein bridge oscillator.

• Newbie
• Posts: 44
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #31 on: May 11, 2014, 04:17:57 AM »
Hi All,

I have redrawn the circuit, and its the current circuit that i am using right now.

If you dont have the parts, just use any parts that come close to them.

The ferrite is a tv flyback ferrite.

Its also the circuit that makes the reverse ringing pattern

Build the circuit and lets share some more, and hopefully go to the next step.

Movie of current circuit and scope shot
http://youtu.be/8_Bal_7F06s

Greets JB

• Newbie
• Posts: 44
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #32 on: May 11, 2014, 04:38:04 AM »
Btw, if i connect the D6 diode the reverse ringing goes away

So first fix the circuit without that D6, the reverse ringing shows also when loading load to the output, but for simple sake dont hook up any load to the output of the ferrite, and first get the same ringing pattern to comfirm this circuit.

Thnx!

Greets JB

#### EMJunkie

• Hero Member
• Posts: 3322
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #33 on: May 11, 2014, 04:57:05 AM »
Negative resistance is a behavior, a transfer function, of a circuit that is powered externally.  Negative resistance means that as the applied voltage increases the current decreases and as the applied voltage decreases, the current increases.  In order to perform stably in oscillators, circuits that exhibit negative resistance are typically combined with limiter circuits.  Once the amplitude builds up to a certain level, the limiter diverts energy non linearly to prevent the amplitude from building to the point that the circuits saturate.  A classic example that uses the non linear resistance of an incandescent bulb is the Wein bridge oscillator.

This is right! Also, and importantly, one must take note of the Difference between Differential Negative Resistance and True Negative Resistance

Differential Negative Resistance: Current Never goes to or below Zero. Non Linear in its appearance.
True Negative Resistance: Current will go below Zero and theoretically can go well below Zero the more Current Drawn. Theorised to be Linear with Current Draw.

I did no see any signs of Negative Resistance in your scope shots.

Don't mix the two as they are quite obviously not the same and in fact not even similar! Its a confusing situation because most people, even scientists don't know the difference!

All the Best

Chris

#### d3x0r

• Hero Member
• Posts: 1433
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #34 on: May 11, 2014, 05:03:01 AM »
It's not negative resistance; it looks like negative resistance.
It could be qualified as negative resistance because there is already an existing signal that is being reinforced.... I guess...
the beware was beware of people that are going to jump on that bandwagon, because that's not really an important feature.

#### EMJunkie

• Hero Member
• Posts: 3322
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #35 on: May 11, 2014, 05:04:56 AM »
Btw, if i connect the D6 diode the reverse ringing goes away

So first fix the circuit without that D6, the reverse ringing shows also when loading load to the output, but for simple sake dont hook up any load to the output of the ferrite, and first get the same ringing pattern to comfirm this circuit.

Thnx!

Greets JB

@JB,

The Ringing you are getting could be the natural ring down of the coil. Be careful not to confuse this with other effects. There are a few ways to check this and eliminate the Ring down of the coil, first, remove the core and check for the same oscillation. NOTE: It will likely be at a different frequency, as the LC, L being Inductance, and C the Coils Natural Distributed Capacitance, will have different values. The Effect will still be there under the same conditions.

EDIT: For clarity, I wanted to point out that the Natural Ring Down of the Coil is a little like the striking of a Bell, Hit it once and the Tone Vibrates on for a period of time....

A few other people on different threads have pointed this out and given the Natural Ring Down of the Coil many fancy names. Of course this is quite simply wrong.

All the Best

Chris
« Last Edit: May 11, 2014, 10:13:28 AM by EMJunkie »

• Jr. Member
• Posts: 62
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #36 on: May 11, 2014, 01:32:32 PM »

transistors BC / p-n-p / , on picture "Image" are drawn wrong.
Emitter can not be connected on minus / ground /.

regards

« Last Edit: May 11, 2014, 07:49:46 PM by madsatbg »

#### MarkE

• Hero Member
• Posts: 6830
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #37 on: May 11, 2014, 01:38:06 PM »
This is right! Also, and importantly, one must take note of the Difference between Differential Negative Resistance and True Negative Resistance

Differential Negative Resistance: Current Never goes to or below Zero. Non Linear in its appearance.
True Negative Resistance: Current will go below Zero and theoretically can go well below Zero the more Current Drawn. Theorised to be Linear with Current Draw.

I did no see any signs of Negative Resistance in your scope shots.

Don't mix the two as they are quite obviously not the same and in fact not even similar! Its a confusing situation because most people, even scientists don't know the difference!

All the Best

Chris
I think you are referring to someone else's scope shots.  I haven't posted any in this thread.  180 degrees phase shift yields the second form.  A high Q network at its SRF can provide such a phase shift.

#### EMJunkie

• Hero Member
• Posts: 3322
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #38 on: May 11, 2014, 01:40:18 PM »
I think you are referring to someone else's scope shots.  I haven't posted any in this thread.  180 degrees phase shift yields the second form.  A high Q network at its SRF can provide such a phase shift.

Apologies MarkE, I was meaning JB's Scope Shots.

All the Best

Chris

#### Vortex1

• Hero Member
• Posts: 518
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #39 on: May 11, 2014, 05:46:51 PM »
Btw, if i connect the D6 diode the reverse ringing goes away

So first fix the circuit without that D6, the reverse ringing shows also when loading load to the output, but for simple sake dont hook up any load to the output of the ferrite, and first get the same ringing pattern to comfirm this circuit.

Thnx!

Greets JB

Congratulations on the reverse ringing, something interesting happening there. Yes D6 is circulating all the power in the 12T winding and diode and using it up. Note that the 7T winding has no flyback diode.

#### d3x0r

• Hero Member
• Posts: 1433
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #40 on: May 12, 2014, 07:14:44 AM »

transistors BC / p-n-p / , on picture "Image" are drawn wrong.
Emitter can not be connected on minus / ground /.

regards
ya; should be npn; so the arrow on the leg is backwards?

#### Jeg

• Hero Member
• Posts: 1532
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #41 on: May 12, 2014, 07:51:19 AM »
Btw, if i connect the D6 diode the reverse ringing goes away

So first fix the circuit without that D6, the reverse ringing shows also when loading load to the output, but for simple sake dont hook up any load to the output of the ferrite, and first get the same ringing pattern to comfirm this circuit.

Thnx!

Greets JB

Remarkable job JB! Thanks for everything! Your efforts and results inspires us too!

#### Vortex1

• Hero Member
• Posts: 518
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #42 on: May 12, 2014, 01:52:22 PM »
ya; should be npn; so the arrow on the leg is backwards?

No should remain pnp, just reverse C-E connections. This is a standard Miller clamp.

Also ground wire needed on source of lower FET.

• Newbie
• Posts: 44
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #43 on: May 12, 2014, 09:53:16 PM »
This is right! Also, and importantly, one must take note of the Difference between Differential Negative Resistance and True Negative Resistance

Differential Negative Resistance: Current Never goes to or below Zero. Non Linear in its appearance.
True Negative Resistance: Current will go below Zero and theoretically can go well below Zero the more Current Drawn. Theorised to be Linear with Current Draw.

I did no see any signs of Negative Resistance in your scope shots.

Don't mix the two as they are quite obviously not the same and in fact not even similar! Its a confusing situation because most people, even scientists don't know the difference!

All the Best

Chris

You are right, cause i have done so many tests and all i can say is that this reverse ringing does not do anything special, besides looking good.

If i change the frequency of ic2 lower the reverse ringing only gets longer and longer, but nothing special.

It doesnt even help with boosting the circuit. Like i said this reverse ringing aint doing anything.

Only amps go a little bit down when connecting the feed back circuit.

But i will keep on trying different setups

Greets JB

• Newbie
• Posts: 44
##### Re: Akula0083 Light No3 - Dual TL494
« Reply #44 on: May 12, 2014, 09:59:53 PM »

transistors BC / p-n-p / , on picture "Image" are drawn wrong.
Emitter can not be connected on minus / ground /.

regards

Thnx for the correction, but i figured that yall would understand, i wanted to use LTSpice for drawing but i did not feel like cause i had to look for all components, so drawing it seemed faster.

Thnx,

Greets JB