PopularFX
Home Help Search Login Register
Welcome,Guest. Please login or register.
2024-04-18, 20:53:13
News: Registration with the OUR forum is by admin approval.

Pages: 1 ... 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 [34] 35 36 37 38 39 40 41 42 43 44 45 46 47 48
Author Topic: Akula0083 30 watt self running generator.  (Read 930650 times)
Group: Guest
@Peterea  I'm not negative .... I was happy for new device...
   

Group: Moderator
Hero Member
*****

Posts: 2736


Buy me a cigar
Dear Peterae.

I agree with your sentiments 100%. I am learning quicker than I have ever done !!  It is with thanks to the members here at OUR, their patience akin to that of Job himself !!  :)

I am now going to tax them even further now !!

Dear Verpies, with reference to our conversation in chat last night. I have dismounted and checked each resistor in the potential divider, all are correct. I still am unable to lower the voltage.

Do you have any suggestions.  Please be aware that R 6 is still lifted on one side whilst these tests were carried out !!

Cheers Grum.


---------------------------
Nanny state ? Left at the gate !! :)
   
Group: Guest
@Peterea  I'm not negative .... I was happy for new device...

I'm interested in Akula's new device also.  If he posts schematic, definitely start thread for it.  O0
   
Group: Guest

@Happy

Thanks for trying the diode at R3. Listen man, it is too complicated for me to explain so while you guys work out the circuit end I will do it myself and prepare the tuning of the coils and set-up a procedure for testing and report back. This part, the hunting part is my specialty and I would have to be standing behind you to explain everything and even then the circuit frequency drive limitations would just drive me crazy. Better to work the output end with full control first, then to bring it into a stand alone. With the set-up below, if I hit a good effect I should be able to remove the battery and make it run even with the FG in place, the point would be made.


wattsup


@ Wottsup,

That's great man, thinking outside the box on the coil design might just do the trick. I look forward to your construction details for a self-running coil design. My setup is at the ready to try any suggested coil design, assuming full constructional details are provided. However, it would not be wise at this stage to assume that there is any error in Akula's schematics insofar as what is necessary for self-running, given a fit for purpose coil design. Its only the coil design details that have not been given to us.

Happy  :)
   
Group: Guest
I'm interested in Akula's new device also.  If he posts schematic, definitely start thread for it.  O0

Its what's inside that SMPS box that interests me.  ;)
   

Group: Administrator
Hero Member
*****

Posts: 3867


Buy me some coffee
Quote
I'm interested in Akula's new device also.  If he posts schematic, definitely start thread for it.  Afro
No problem guys, just PM me a title and i will start one when we need to.

Tutorial_FE thanks for clarifying your position  O0
   

Group: Professor
Hero Member
*****

Posts: 3359
Dear Verpies, with reference to our conversation in chat last night. I have dismounted and checked each resistor in the potential divider, all are correct. I still am unable to lower the voltage.  Do you have any suggestions.  
Check that R14 and R15 are connected according to the diagram below and have resistances that are written next to them on this diagram.
If still no luck, than make a high resolution photo (or scan) of the components and traces marked in red (put R14, R15 and R6 back into the board for the photo)

Component designations are in accordance with Groundloop's PCB.
« Last Edit: 2014-04-20, 18:52:36 by verpies »
   
Hero Member
*****

Posts: 520
The Sunday Akula Review - hahaha

@Itsu (but also @Grum - @Happy)

About the spikes, where is your copper strip grounded? On the diagram it shows the copper strip grounded at C3.  I don't know if that would make any difference when this strip will receive some static discharges from the the shock treatment of the Ecore.  Maybe we need to add something between the copper strip and ground to kill or attenuate the spike before it hits the ground since in essence this is a floating ground system? Or send the copper strip connection to a real ground off the circuit to see if the spike will go away. Don't know.

Also, in most of Akulas' devices he has the transformer off and away from the board. Maybe you need to extend your 5 transformer wires to place it further away from the board since maybe its air static from L1/L2 towards the L1 choke then feeding into the VR1. Or as you are pulsing, move the transformer to see if there are any angles that influence the spike. Or place a metal plate between the transformer and the board to see if more shielding makes a difference just to see if the source is the transformer via air.

Also, for all builders, please remind us what type of winding you have, T1000 or standard mode. It may be good to eventually make up a build model number that builders can include in each of their posts (or temporarily in their signature) so we always know the device type and not have to ask ourselves this question after a few more pages. hahaha Or put a URL in your signature where you have posted a build summary.

Maybe something like.........

Four letter model designation: AK30 - AK01 - AK??
Characters 1 and 2 for circuit board type: GL = @Groundloop - SH = Shark-01 - FB = Free board - others
Characters 3 and 4 for diagram type: ???????? to be determined by @verpies.
Characters 5 and 6 for transformer type: EC = Ecore - CC = Ccore SC = Straight core - others
Characters 7 and 8 for wind type: T2 = T1000 mode with two layers secondary below the primary - S1 = Standard mode - others to be determined.
Characters 9 to 12 for primary and secondary turns: 1545 would mean 15 turns primary and 45 turns secondary.

So if a builder uses AK30-GL-??-EC-T2-1554 we will know right away your build type and not have to remember this or ask you the same thing. Or maybe just summarize your build in your signature any way you want.

- Coil Winding Methods and Logic -

By the way the Akula circuit is working, seems to me the L2 has to react after the L1 pulse not at the pulse, then the winds must be Standard Mode so L2 can work on its own half of the core out of phase to L1.

In the T2 mode I cannot see why you want to have the L1 pulse hit the L2 two layers under L1 right away as L1 hits its half of the core, you are in essence hitting the L2 at the same time and both fluxs leave their center gap and will cancel out on the ecore ends if you have no coils on the ecore ends to pick it up. Does not make sense. I would want the L2 to be fully reactive to the Ecore movements and not mix it up by also being on the L1 side.

If L2 is over the gap -

If L1 is left of gap and L2 is right of gap, at most, I would say go with a T1 mode,  I would not wind more then one layer of L2 under L1 and wound from furthest left of L1 side to furthest right on L2 side then build up the rest of the L2 winds on the right. This way only one layer of L2 is exposed under the L1 pulse making it perfectly directional and not like it is now with two L2 layers pushing in two directions when L1 hits. The only other variable with one layer L2 from left is when you get to the gap, reverse direction and continue the L2 on the right side making it a first layer bucking mode that should keep the same direction even if moved from flux of two gap sides. That adds another variable to the build.

Just my opinion but I will be testing a standard tuning and wind method first.

@verpies

Thanks a heep. Now I know how it works. D6 R2 C4 is a voltage splitter (and virtual ground) sharing the output between L2 and the load. R3 is basically a recharge regulator. But I would still add a diode between R3/C11 and facing C11. I would not want any chance of R3 feeding into L2 in case D6 went into reverse threshold mode.

Also can R3 value be changed to pass more back to C11. Seems to me this should remain a major variable that needs to be tuned specifically to each device. If in Build 1 the L2 produces less recharge then in Build 2, then R3 should be able to let more pass to C11 in Build 1 then in Build 2.

The other variable I am seeing is this. D6 could also work if installed in reverse since with the Q1 short circuit, you can expect high voltages to forward pass D5 and possibly hitting the reverse threshold of D6 to fill L2 and (help) recharge C11 along with L2s regular output from L1 flux transfer.

@ALL

Reality Check:

Also, I took a close up shot of the original Akula30 circuit board to match his components to the diagram since I wanted to see this first before I set-up for my testing. I am very puzzled to see right away there is only one big diode there. How is that possible that on the circuit diagram there are two D5 and D6? I think it may be good to inspect the photo and try to trace the components to the diagram to see where the diagram is adding more components or diverging from the diagram.

Seems to me if Akula used his live board to make the self-runner and if the live board does not concord to the circuit diagram, and if Akula did not afterwards modify his live board to reflect the published diagram and then re-do his tests to make sure it is still self-running and all this done before publishing that diagram, then the diagram becomes an unproven variation of the original live board. That is not good because it means the diagram is not proven except by x_name41 who had to fake his demo when using that diagram. Just trying to cover all the bases. At this point I cannot trust Akula to be so forthcoming as to give exact details of his builds. He is probably getting a self-runner but when diagrams do not follow the actual build, we have to presume the inventor is playing a game of "I did it this way but you should try to do it that way and see if it works". I hate playing games when it comes to such matters, I would prefer to see exactly how Akula physically did it and not how he made his diagram. Diagrams do not produce OU.

You see, unfortunately we are caught in the middle of something that has varying interests. I am sure Akulas' main interest is to make some money with this, otherwise he would be more open and his diagrams would be 100% accurate and we would already have circuits coming out of China in container loads. But by the same token he needs the worldwide exposure to attract those money guys but he surely does not want to spill all the beans to keep control. So he shows an OU effect and puts down a diagram. Follow the diagram and good luck. If you need any direct assistance this increases demand for his direct intervention that could then be negotiated in his favor. OU forces melding with personal economic forces changes the game and puts the onus on us to try and see through the haze of interests. It is not easy when a guy sees this as a form of potential revenue for his family while trying to get exposure and not spill all the beans. The irony of all this is that our effort here is basically based on a non-proven diagram that we know had been faked by a second party.  This for Akula is a good situation. He says use 1 ohm for R3 but he probably knows that a better value is required based on the recharge potential. But if builders do not wise up on those notions because we "stick to the diagram and values", we could be here for a long time before a self-runner is on the plate.

@Peterae

Truth is never negative. Better to be aware of the counter forces then to rely on blind faith. Sometimes I spend hours on SM videos close up trying to find a new lead for @GK or my FTPU tests, each lead adds to the others. In this case all we have is one real photo and a host of diagrams that do not reflect the real photo. So somewhere, somehow we have to see through this and realize, this is not a replication but 1/4 replication and 1/4 re-creation and 1/2 pure R&D. That's what Akula expects us to do to make it work. That's the reality.

But I have such a good feeling about this because at least he put down the basic out-of-the-box principle and this can be tried in many ways, not only as per the diagrams. I could even try a more passive variation of this in the FTPU or in any other build. So it's still good but "no free lunch'". Akula is playing a very delicate balancing act and he is doing it very well. He probably learned from TKs demise. Show you're open but don't say it all to give it away. As long as we are wise to the game to realize the diagram is not 100% and changes will be required, we should be OK.

Sorry for long post. I'll put myself on voluntary mute mode so I won't distract you guys any more then I have already until I get my testing up so, back to the bench.

wattsup


---------------------------
   

Group: Moderator
Hero Member
*****

Posts: 2736


Buy me a cigar
Check that R14 and R15 are connected according to the diagram below and have resistances that are written next to them on this diagram.
If still no luck, than make a high resolution photo (or scan) of the components and traces marked in red (put R14, R15 and R6 back into the board for the photo)

Component designations are in accordance with Groundloop's PCB.

Dear Verpies.

Thanks for the info. I removed the TL 494 and expected to see between pins 1 and 16 a variable resistance of 2K up to 6.7 K instead I got a slowly rising resistance, rather like charging a cap, this does not compute !!  :) As I should see just the fixed 2K and the variable 4.7 K and nothing else. Am I correct in this assumption ?

Cheers Grum.


---------------------------
Nanny state ? Left at the gate !! :)
   
Sr. Member
****

Posts: 336
Dear Verpies.

Thanks for the info. I removed the TL 494 and expected to see between pins 1 and 16 a variable resistance of 2K up to 6.7 K instead I got a slowly rising resistance, rather like charging a cap, this does not compute !!  :) As I should see just the fixed 2K and the variable 4.7 K and nothing else. Am I correct in this assumption ?

Cheers Grum.

Grum,

Cold solder on socket pin 16?

GL.
   

Group: Professor
Hero Member
*****

Posts: 3359
Thanks for the info. I removed the TL 494 and expected to see between pins 1 and 16 a variable resistance of 2K up to 6.7 K instead I got a slowly rising resistance, rather like charging a cap, this does not compute !!  :) As I should see just the fixed 2K and the variable 4.7 K and nothing else. Am I correct in this assumption ?
You are correct.
There should not be any cap connected to pin 1 (even inadvertently)
   

Group: Moderator
Hero Member
*****

Posts: 2736


Buy me a cigar
Dear Verpies, Groundloop and all.

I think I have finally "Sussed" it !!  O0

It seems there is an error in the overlay drawing with regards to the GL schematic. The resistors are labelled as R14 (Nearest to duty pot) and R 15 above (R14), on overlay drawing. In fact the 12K resistor should be fitted closest to the duty pot (R15) and the 2K above!!

The upshot is that now I can bring up the voltage to 12 V and shut off the pule train with the duty pot !! HOORAY !!  :)  However I am not seeing a diminishing of pulse width ??  But I had not reconnected R6 !!

It has been a very busy day for me, feeding the 5000 !! I will resume testing tomorrow, once again thanks for all the input.  O0

Cheers Grum.


---------------------------
Nanny state ? Left at the gate !! :)
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 4092
The Sunday Akula Review - hahaha

@Itsu (but also @Grum - @Happy)

About the spikes, where is your copper strip grounded? On the diagram it shows the copper strip grounded at C3.  I don't know if that would make any difference when this strip will receive some static discharges from the the shock treatment of the Ecore.  Maybe we need to add something between the copper strip and ground to kill or attenuate the spike before it hits the ground since in essence this is a floating ground system? Or send the copper strip connection to a real ground off the circuit to see if the spike will go away. Don't know.

Also, in most of Akulas' devices he has the transformer off and away from the board. Maybe you need to extend your 5 transformer wires to place it further away from the board since maybe its air static from L1/L2 towards the L1 choke then feeding into the VR1. Or as you are pulsing, move the transformer to see if there are any angles that influence the spike. Or place a metal plate between the transformer and the board to see if more shielding makes a difference just to see if the source is the transformer via air.


Hi wattsup,

i was fighting these spikes this afternoon, but manipulating the copper strip does not seem to influence them.
I can remove the copper strip connection from the board and/or connect it to real ground, but the spikes remain.

Disconnecting 1 side of L1 (choke) clears these spikes.

I used some 0.1uF ceramic caps directly across pins11/12 to 7 of the TL494 and made a solid stranded wire directly from pin 7 to minus
Also a 0.1uF ceramic cap across the 7812 out and ground pins did not clear it up, so i guess i have some violations against the star ground concept.

This means i have to redo the whole ground system of my board, so i will leave it for the time being.
Hopefully the PCB's are better designed so you won't have these spikes.

Regards Itsu
« Last Edit: 2014-04-20, 21:40:22 by Itsu »
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 4092
You still have the L1 and L2 currents reaching maxima and zeros simultaneously.  That's a characteristic current transfer in a "normal transformer".  That transformer mode is wrong in my opinion.
For a "flyback transformer" mode (the correct one IMO), L2 should be reversed and these waveforms should look like this:



Ch1 (yellow) : Gate voltage in reference to ground
Ch2 (blue)    : Voltage across R1 (0.2 Ohm), with C2 removed (L1 Current)
Ch3 (green)  : Voltage across R3 (1 Ohm) (L2 Current)

OK,  i swapped L2 connections and redid the current measurements using R1 and R3 as CSR's (C2 disconnected).

Ch1 (yellow) gate signal,   groundless as the other to probes grounds are at +12V level, so its somewhat distorted and just for reference.
Ch2 (blue) = voltage across R1, with C2 removed (L1 Current)
Ch4 (green) = voltage across R3 (L2 current)

Regards Itsu
   
Sr. Member
****

Posts: 336
Dear Verpies, Groundloop and all.

I think I have finally "Sussed" it !!  O0

It seems there is an error in the overlay drawing with regards to the GL schematic. The resistors are labelled as R14 (Nearest to duty pot) and R 15 above (R14), on overlay drawing. In fact the 12K resistor should be fitted closest to the duty pot (R15) and the 2K above!!

The upshot is that now I can bring up the voltage to 12 V and shut off the pule train with the duty pot !! HOORAY !!  :)  However I am not seeing a diminishing of pulse width ??  But I had not reconnected R6 !!

It has been a very busy day for me, feeding the 5000 !! I will resume testing tomorrow, once again thanks for all the input.  O0

Cheers Grum.

Grum,

I have checked and there is no error in the component values.
R15 (12K) is closest to variable resistor. R14 (2K) above that.

The main reason that I did not include the component labeling at
the silk screen was to avoid just such problems. Sometimes EAGLE
display the component numbering all over the place and it is a lot
of work "smashing" the components and manually move the numbering
around for a better view. EAGLE CAD is a free downloadable program.
When you solder the board, then you use the program to see what
components to solder where. That was the main idea.

The symptoms you did discovered when using a Ohm meter at pin 1
on the socket to pin 16 was a "floating" value. So when you did re-solder
the resistors to the correct position, then you most probably did get
a good solder connection for the ground of R14.

But I'm glad that you solved your problem.

GL.
 
   

Group: Professor
Hero Member
*****

Posts: 3359
I have checked and there is no error in the component values.  R15 (12K) is closest to variable resistor. R14 (2K) above that.
...but on the image of the PCB, the designator R14 is closer to the 12k resistor ...and the designator R15 is closer to the 2k resistor.
Its not surprising that Grum (and one other person) had wrongly followed these designators according to their proximity to the resistor.

If 2 persons make the same mistake, then it is a good indicator that they were confused by the same issue during the assembly.
These designators need to be addressed in v2 of the PCB.
   

Group: Professor
Hero Member
*****

Posts: 3359
OK,  i swapped L2 connections and redid the current measurements using R1 and R3 as CSR's (C2 disconnected).
Ch1 (yellow) gate signal,   groundless as the other to probes grounds are at +12V level, so its somewhat distorted and just for reference.
Ch2 (blue) = voltage across R1, with C2 removed (L1 Current)
Ch4 (green) = voltage across R3 (L2 current)
Now the waveforms look well.  Note the flat tops and rising ramps in L2 current waveform at the ends of the OFF period.  They are significant.
The magnitude of L2 current and the length of an interval during which this current flows, is proportional to the energy that is being returned to C11 - treat it as your payback.

A video of these waveforms at different supply voltages and DTY pot settings with and without the LED load would be nice at this point.
If you want to generate more raw experimental data as food for thought, you can try temporarily substituting an automotive bulb in lieu of the LED bank.
I know this circuit is not designed to operate with resistive loads, but it will not break.

In theory, you should see some narrow strong negative "magic" pulses in L2 current (during the same scoping arrangement as here) when the circuit is correctly tweaked with its potentiometers and its transformer is constructed correctly (the most difficult part IMO).
« Last Edit: 2014-04-21, 01:14:02 by verpies »
   

Group: Professor
Hero Member
*****

Posts: 3359
I think I have finally "Sussed" it !!  
Good, now you can have the satisfaction of solving the problem for yourself and for others.  O0

The upshot is that now I can bring up the voltage to 12 V and shut off the pule train with the duty pot !! HOORAY !!  :)  However I am not seeing a diminishing of pulse width ??  But I had not reconnected R6 !!
You can reconnect R6 and the MOSFET's gate resistor now, but it will not make the DTY pot control the duty cycle like you expect.

Before you proceed further make sure that your L2 winding polarity is according to the dot convention in Fig.2 or such that you get L1 & L2 current waveforms like Itsu here.

The DTY pot controls the sensitivity of MOSFET's duty cycle reduction in response to the following events:
1) The C6 is overcharged by pulses coming from L2 via D6.  Not when C6 is overcharged by your external power supply!!!, or...
2) The L2 generates a negative pulse with a very steep falling edge ("negative" refers to the "down direction" on this scope shot of Ch4 ), or...
3) The negative pulse from L2 is so strong that it completely discharges C10 to zero ...or charges it negatively.

( Events described in pt.2 and pt.3 are brought into the TL494 by R6 ).


P.S.
On Akula's diagrams C6=C11 and C10=C3 and R6=R7.
The strong negative pulse generated by L2 is that "magic pulse" that is not predicted by conventional electronic engineering rules and transformer theory.

« Last Edit: 2014-04-21, 10:36:34 by verpies »
   
Sr. Member
****

Posts: 336
...but on the image of the PCB, the designator R14 is closer to the 12k resistor ...and the designator R15 is closer to the 2k resistor.
Its not surprising that Grum (and one other person) had wrongly followed these designators according to their proximity to the resistor.

If 2 persons make the same mistake, then it is a good indicator that they were confused by the same issue during the assembly.
These designators need to be addressed in v2 of the PCB.

These designators are now addressed in v2 of the PCB.
   
Sr. Member
****

Posts: 281
I did just that, but besides a cleaner drain voltage signal (nice square wave, so no more jump half way) no noticeable other effects are seen.

Regards Itsu

Good day Itsu,
Funny you should mention the change in the Drain waveform.....   So, changing position of C11 to the *opposite* side of  L3 (Choke number according to Verpies *new* schematic) diminished or eliminated the aberration that appeared about half-way thru the OFF pulse that was discussed by Verpies and I earlier?

Unfortunately, regarding resonant systems it is usually impossible to just throw one together with random values,(Inductive & Capacitive reactance) and expect it to be in resonance.  So it is not surprising that you noticed nothing out of the ordinary......

It really makes me wonder why the photo on the 30 watt Akula schematic does NOT depict ALL the parts that are listed on the same schematic.......

take care, peace
lost_bro
   
Group: Guest

It really makes me wonder why the photo on the 30 watt Akula schematic does NOT depict ALL the parts that are listed on the same schematic.......

take care, peace
lost_bro

Maybe to deepen the confusion.  :-\
   
Group: Guest
Maybe to deepen the confusion.  :-\

Akula's last video with the separate power supply is the same way.  When he takes the device outside and places it on the tree stump, he puts down a schematic first that clearly has three integrated circuits, but the board he is showing has only two.  I went through that video frame by frame and found a hex inverter chip, a PLL and a half bridge driver with a center-tapped transformer.  Maybe we will see a running demo of that device in the future.
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 4092
Now the waveforms look well.  Note the flat tops and rising ramps in L2 current waveform at the ends of the OFF period.  They are significant.
The magnitude of L2 current and the length of an interval during which this current flows, is proportional to the energy that is being returned to C11 - treat it as your payback.

A video of these waveforms at different supply voltages and DTY pot settings with and without the LED load would be nice at this point.
If you want to generate more raw experimental data as food for thought, you can try temporarily substituting an automotive bulb in lieu of the LED bank.
I know this circuit is not designed to operate with resistive loads, but it will not break.

In theory, you should see some narrow strong negative "magic" pulses in L2 current (during the same scoping arrangement as here) when the circuit is correctly tweaked with its potentiometers and its transformer is constructed correctly (the most difficult part IMO).

Ok, here some specifics on how i have the transformer constructed and connected, see picture and video:
https://www.youtube.com/watch?v=lJTxEPuNIlk&feature=youtu.be

Fine tuning still will be a problem as the high current prevents me from doing long ontime measurements.
yesterday i had it on to long while tuning the dty pot R11 (no change in the currents during that tuning), and thick smoke came up from C6 / VR1 area   :D

Anyway,  thanks for the guidance up till now,  its much appreciated.


Regards Itsu
   

Group: Elite Experimentalist
Hero Member
*****

Posts: 4092
Good day Itsu,
Funny you should mention the change in the Drain waveform.....   So, changing position of C11 to the *opposite* side of  L3 (Choke number according to Verpies *new* schematic) diminished or eliminated the aberration that appeared about half-way thru the OFF pulse that was discussed by Verpies and I earlier?

Unfortunately, regarding resonant systems it is usually impossible to just throw one together with random values,(Inductive & Capacitive reactance) and expect it to be in resonance.  So it is not surprising that you noticed nothing out of the ordinary......

It really makes me wonder why the photo on the 30 watt Akula schematic does NOT depict ALL the parts that are listed on the same schematic.......

take care, peace
lost_bro

Correct, the drain voltage now was as clean as the gate signal, nice square signal.
I did not take a screenshot, and i had to revert back to the normal C11 position to make these last current measurements, as with C11 at the other side of the choke,
the current measurements where skewed, probably because the ground leads also had to be moved to c11 (before the choke).

Regards itsu
   
Group: Elite
Hero Member
******

Posts: 3537
It's turtles all the way down
I cannot access the latest Akula video's as they now seem to be "private". Or is it something wrong on my end?

Hope someone saved them.


---------------------------
"Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy
   
Pages: 1 ... 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 [34] 35 36 37 38 39 40 41 42 43 44 45 46 47 48
« previous next »


 

Home Help Search Login Register
Theme © PopularFX | Based on PFX Ideas! | Scripts from iScript4u 2024-04-18, 20:53:13