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Author Topic: Akula0083 30 watt self running generator.  (Read 441498 times)
Sr. Member
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Posts: 337
I have finished the control part (TL494IN) of the AKULA 30W circuit.
Frequency can be adjusted between 16 and 116KHZ at 12V with the 10K Ohm potmeter (too high?).

But the 5K potmeter does not seem to change the pulse width, allthough the voltage on pin 1 changes from 1V to 4V.

I seem to have a problem with the 12V voltage regulator as sometimes the voltage output on it drops from 12 to 10V

Most parts are as mentioned on the diagram, however a few resistors are the first close in the range (like 6.8 Ohm for the 7 Ohm etc)

I show the input voltage from a battery on a DMM and the output voltage of the 12V regulator also on a DMM.
Scope probes are used to measure:
# the output from pin 11 (after the pull up resistor) (yellow probe)
# the signal on pin 1 (used for the Pulse width) (blue probe)
# the signals on all the 16 pins of the TL494 one after the other (purple probe)

Video here:  https://www.youtube.com/watch?v=R2r0en-kC3M&feature=youtu.be

Comments are welcome especially why the pulse width is not changing (is it because the pinned to ground via R7/R5 of pin 15?)  


Regards itsu

Itsu,

I did misread the circuit drawing The two 4K are in series. So what you are seeing on pin 2 is VREF.
How can the comparator work if this voltage always is VREF?

GL.
   
Full Member
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Posts: 116
Itsu,

I did misread the circuit drawing The two 4K are in series. So what you are seeing on pin 2 is VREF.
How can the comparator work if this voltage always is VREF?

GL.

Hello All:

I agree with Groundloop:


The pulse width modulator comparator provides a means
for the error amplifiers to adjust the output pulse width from
the maximum percent on−time, established by the deadtime
control input, down to zero, as the voltage at the feedback
pin varies from 0.5 V to 3.5 V. Both error amplifiers have a
common mode input range from −0.3 V to (VCC − 2V), and
may be used to sense power−supply output voltage and
current. The error−amplifier outputs are active high and are
ORed together at the noninverting input of the pulse−width
modulator comparator. With this configuration, the
amplifier that demands minimum output on time, dominates
control of the loop.


This is from ON-semi spec. sheet TL494.

Take care, peace
lost_bro
   
Sr. Member
****

Posts: 337
Hello All:

I agree with Groundloop:


The pulse width modulator comparator provides a means
for the error amplifiers to adjust the output pulse width from
the maximum percent on−time, established by the deadtime
control input, down to zero, as the voltage at the feedback
pin varies from 0.5 V to 3.5 V. Both error amplifiers have a
common mode input range from −0.3 V to (VCC − 2V), and
may be used to sense power−supply output voltage and
current. The error−amplifier outputs are active high and are
ORed together at the noninverting input of the pulse−width
modulator comparator. With this configuration, the
amplifier that demands minimum output on time, dominates
control of the loop.


This is from ON-semi spec. sheet TL494.

Take care, peace
lost_bro

lost_bro,

How can we fix this? I think there is a fault in the circuit drawing. My best guess is that
the R6 and R8 should be a voltage divider (1/2) for the VREF so that pin 2 on the IC
will have 1/2 the VREF. Then we can adjust the pot-meter R11 and change the duty cycle.

OR is the other comparator overriding the first one because of no positive feedback via R7?

GL.  
   
Full Member
***

Posts: 116
lost_bro,

How can we fix this? I think there is a fault in the circuit drawing. My best guess is that
the R6 and R8 should be a voltage divider (1/2) for the VREF so that pin 2 on the IC
will have 1/2 the VREF. Then we can adjust the pot-meter R11 and change the duty cycle.

GL. 

Hello Groundloop

This circuits works:

take care, peace
lost_bro
   
Sr. Member
****

Posts: 337
Itsu,

Can you try this:

Connect a pot-meter (10K) between VREF and GND. Feed the
center tap of the pot-meter to R7. (Ground to R7 removed).
Then try your duty cycle pot-meter.

This test pot-meter will simulate the output current that
flows through the R5 thus resulting av positive voltage
over the C5 electrolytic capacitor.

If my theory is correct then the duty cycle ON time should be
smaller when the voltage input to R7 is going UP.

GL.
   
Full Member
***

Posts: 116
lost_bro,

How can we fix this? I think there is a fault in the circuit drawing. My best guess is that
the R6 and R8 should be a voltage divider (1/2) for the VREF so that pin 2 on the IC
will have 1/2 the VREF. Then we can adjust the pot-meter R11 and change the duty cycle.

OR is the other comparator overriding the first one because of no positive feedback via R7?

GL.  

Yes, I believe that is correct, as when I have used the TL494 I connect pin #14 directly to pin #15 as in the pic that I attached.
Does NOT make sense to have R6 between #14 and #15.

So R6 and R8 can be configured as a Voltage divider for Pin #2....

take care, peace.
lost_bro

Must be a drawing oversight on the schematic.......
   
Sr. Member
****

Posts: 337
Yes, I believe that is correct, as when I have used the TL494 I connect pin #14 directly to pin #15 as in the pic that I attached.
Does NOT make sense to have R6 between #14 and #15.

So R6 and R8 can be configured as a Voltage divider for Pin #2....

take care, peace.
lost_bro

Must be a drawing oversight on the schematic.......

lost_bro,

I would like to see Itsu test the "load simulator" first before I conclude about the error.

Itsu, du you have time to test a 10K pot-meter as I described above?

GL.
   

Hero Member
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Posts: 1130
lost_bro,

I would like to see Itsu test the "load simulator" first before I conclude about the error.

Itsu, du you have time to test a 10K pot-meter as I described above?

GL.

Hi GL,   yes i can do that.

I will report back what i found,  but it takes some time (hours)

Regards Itsu
   
Newbie
*

Posts: 12
lost_bro,

How can we fix this? I think there is a fault in the circuit drawing. My best guess is that
the R6 and R8 should be a voltage divider (1/2) for the VREF so that pin 2 on the IC
will have 1/2 the VREF. Then we can adjust the pot-meter R11 and change the duty cycle.

OR is the other comparator overriding the first one because of no positive feedback via R7?

GL.  
Hi GL,

My simulation (still an ongoing process) showed exactly that. Pin 2 on tl494 has to have an additional 4.7 k resistor to ground for the pwm to work.

Cheers,

Black Bird
   
Sr. Member
****

Posts: 337
Hi GL,   yes i can do that.

I will report back what i found,  but it takes some time (hours)

Regards Itsu

Itsu,

Thanks. Looking forward to your test.

GL.
   
Sr. Member
****

Posts: 337
Hi GL,

My simulation (still an ongoing process) showed exactly that. Pin 2 on tl494 has to have an additional 4.7 k resistor to ground for the pwm to work.

Cheers,

Black Bird

Black Bird,

Thanks for doing simulations.
The extra resistor can easily be added to the PCB by soldering it on the underside of the PCB.

GL.
   

Hero Member
*****

Posts: 1130

Ok,  first tried Black_Birds solution by simple adding a 3.9K resistor from pin 2 to ground.
Indeed the voltage on pin 2 now halfs to 2.5V, but the 5K potmeter only reacts in the middle and is very touchy.
Duty cycle switches from 55% in a fraction of a turn to no signal (flat +12V) at all.
No way to set it inbetween (55 -> 1).

Then i tried GL's solution, by disconnecting R7 from the link to R5 (ground) and attaching there the middle tap of a (in my case ) 20K pot-meter.
The both ends of this pot-meter where connected to pin 14 (REF) and pin 7 (ground).
I see the voltage on this center tap (and thus on pin 15) vary between 5V and ground,  but no change in the duty cycle.   :(

Regards itsu

   
Sr. Member
****

Posts: 337
Ok,  first tried Black_Birds solution by simple adding a 3.9K resistor from pin 2 to ground.
Indeed the voltage on pin 2 now halfs to 2.5V, but the 5K potmeter only reacts in the middle and is very touchy.
Duty cycle switches from 55% in a fraction of a turn to no signal (flat +12V) at all.
No way to set it inbetween (55 -> 1).

Then i tried GL's solution, by disconnecting R7 from the link to R5 (ground) and attaching there the middle tap of a (in my case ) 20K pot-meter.
The both ends of this pot-meter where connected to pin 14 (REF) and pin 7 (ground).
I see the voltage on this center tap (and thus on pin 15) vary between 5V and ground,  but no change in the duty cycle.   :(

Regards itsu



Itsu,

Thank you for testing. Keep your 20K "current simulator" connected and try both, add the voltage divide
resistor and then try out different settings for the 20K and the duty cycle pot-meter.

GL.
   

Hero Member
*****

Posts: 1130
Itsu,

Thank you for testing. Keep your 20K "current simulator" connected and try both, add the voltage divide
resistor and then try out different settings for the 20K and the duty cycle pot-meter.

GL.

No problem,     ok,  both solutions together, 2.5V on pin 2 and variable voltage (5 - 0v) on pin 15, but it does not matter how i set this pin 15 voltage, the 5K pot-meter still shows this sudden switch from 55% dc to flat 12V.

Added,  this "switch" happens with exactly 2.5V on pin 1

Regards Itsu
   
Newbie
*

Posts: 12
Ok,  first tried Black_Birds solution by simple adding a 3.9K resistor from pin 2 to ground.
Indeed the voltage on pin 2 now halfs to 2.5V, but the 5K potmeter only reacts in the middle and is very touchy.
Duty cycle switches from 55% in a fraction of a turn to no signal (flat +12V) at all.
No way to set it inbetween (55 -> 1).

Then i tried GL's solution, by disconnecting R7 from the link to R5 (ground) and attaching there the middle tap of a (in my case ) 20K pot-meter.
The both ends of this pot-meter where connected to pin 14 (REF) and pin 7 (ground).
I see the voltage on this center tap (and thus on pin 15) vary between 5V and ground,  but no change in the duty cycle.   :(

Regards itsu
Hi Itsu,

Try to ground pin 15 directly, without the 270 ohm resistor. I'm having problems in the simulation when the 270 ohm is in place.

Cheers,

Black Bird.


   

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Posts: 1130
Black_Bird,  ok only your solution, but then with pin 15 grounded directly.
Still the same, at 2.5V on pin 1 it flips over from 55% dc to flat +12V

 

When i remove both solutions and short pins 2 and 3, then i can vary the dc between 65% and 95%

Ok enough for today, thanks for all your suggestions.


Regards Itsu
   
Sr. Member
****

Posts: 337
No problem,     ok,  both solutions together, 2.5V on pin 2 and variable voltage (5 - 0v) on pin 15, but it does not matter how i set this pin 15 voltage, the 5K pot-meter still shows this sudden switch from 55% dc to flat 12V.

Added,  this "switch" happens with exactly 2.5V on pin 1

Regards Itsu

Itsu,

OK, thanks for testing. We need at some point to sort out what changes to make
to get a correct duty cycle regulation both when tuning R11 and on the feed back
line through R7.

GL.
   
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Posts: 2106
Welcome also, FromOther Planet!
@all - good comments.
 
PS - Jean -- keep up those studies. 
   
Sr. Member
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Posts: 337
@All,

I think this is the solution to the duty cycle problem:

Do not use C2 and C3.
Do not use R5, R8 and R9.
Solder wire at C3 and R8.
Solder R15 standing vertically on the PCB connected to R13.
Solder wire from to of R15 to VREF on pin 14 on TL494.
Add 100nF capacitor from pin 1 to ground.

I referencing to the component labels on MY posted design, the one we are making PCB to.
After the modification the circuit will look like the attached drawing.

I have changed the layout for the experiment board posted one page back.

Comments.................???

GL.
   
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Posts: 246
Are you sure you want duty cycle variable ? can you explain why ? I think it is not needed, just frequency regulation is enough.
   
Sr. Member
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Posts: 337
Are you sure you want duty cycle variable ? can you explain why ? I think it is not needed, just frequency regulation is enough.

Hi Forest,

It is not about what I want, but about what Akyla0083 wanted when he designed his circuit.
So my first attempt to replicate this circuit will be using the same parts (or a close as possible)
on the PCB and see what happens. Later on we can change tings around.

GL.
   
Full Member
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Posts: 246
Do you have Multisim 12 or do you able to get it to test simulation ?  C.C
   

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Posts: 1130
I like what user MenofFather says on overunity.com here:

http://www.overunity.com/14378/akula0083-30-watt-self-running-generator/msg394343/#msg394343

He points out that this R5 (and C5) in the original diagram could be an automatic duty cycle adjuster depending on the load, he says
as a reaction on this post from T1000:

T1000
Quote
P.S> The function of C5 + R5 is still not clear to me in original circuit. Perhaps the intention was to manipulate duty cycle with this feedback path?

MenofFather:
Quote
How I understand, this function change duty cycle depending on load. Wihout load 0 precents duty cycle, with small load let say 20 precents, with big lload let say 60 precents.

So a changing voltage on pin 15 via R7 could/should vary the d.c.
And its an essential part of the circuit as it regulates depending on the current drawn.

Any thoughts?

Regards Itsu
   
Sr. Member
****

Posts: 337
I like what user MenofFather says on overunity.com here:

http://www.overunity.com/14378/akula0083-30-watt-self-running-generator/msg394343/#msg394343

He points out that this R5 (and C5) in the original diagram could be an automatic duty cycle adjuster depending on the load, he says
as a reaction on this post from T1000:

T1000
MenofFather:
So a changing voltage on pin 15 via R7 could/should vary the d.c.

Any thoughts?

Regards Itsu

Itsu,

Yes, that is also my understanding of the R5/C5. The voltage over C5 will be more positive
as the current through R5 increases. This positive voltage is feed back via R7 to the negative
input of the error amplifier 2. The positive pin of the error amplifier 2 is grounded.

Does your 20K pot-meter has any impact on the duty cycle if you wire up your circuit as
shown in my posted image above?

GL.
   

Hero Member
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Posts: 1130
Does your 20K pot-meter has any impact on the duty cycle if you wire up your circuit as
shown in my posted image above?

Well,  that's not that easily done, as it needs substantial (re)moving parts/connections on my tightly soldered print  :(
Perhaps its faster done in a simulator.

Would this feedback link to pin 15 not be more appropriate to be connected to pin 3 (feedback)?

Anyway, it will have to wait till tonight as i am at work right now.

Regards Itsu
 
   
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