DSRD pulse generator

[Peterae]

Nice work Itsu.

Grumpy is the Avalanche expert, we did quiet a bit with it at one point

I built a Marx Avalanche stack, add more stacks and you get higher voltage/ Energy dumped, very easy to build.

http://www.overunityresearch.com/index.php?topic=307.msg9605#msg9605

Looks like i am getting a fall rate of about 18nS for the 1K load @ 740V pulse

I have never tried driving a HHO cell but still have the electronics that i built  

Peter

[ion]

Itsu:

The local power supply bypass capacitor 0.1 uF shown on the schematic is an important part of the original circuit.

I don't see a local power supply bypass capacitor on your ground plane board. As it is now, your power supply leads will contribute some inductance, and you should not get a perfect pulse. This should be a good quality film type of 0.1 uF or tantalum may also work well or other low esr cap.

Scope ground leads will also have some inductance, so best to use a direct BNC to BNC connection to the scope.

Spiral trimmed resistors also could add some inductance to the output circuit. The output 50 ohm would best be a carbon slug rather than carbon film or metal film spiral trimmed types.

This may or may not improve the pulse, there are other variables. You might also try a short length of coax as the storage capacitor for a more square pulse.

[Grumage]

Nice work Itsu.

Grumpy is the Avalanche expert, we did quiet a bit with it at one point

I built a Marx Avalanche stack, add more stacks and you get higher voltage/ Energy dumped, very easy to build.

http://www.overunityresearch.com/index.php?topic=307.msg9605#msg9605

I have never tried driving a HHO cell but still have the electronics that i built  

Peter

Dear Peter.

I have a multi cell device I built a number of years back just waiting for some electronics ! !  

With the huge amount of " FUEL " that has fallen lately, Bank Holiday weather!!    Perhaps we can come to some arrangement?

Cheers Graham.

[Peterae]

Hi Grumage

Indeed dont we always get loads of fuel on Bank Holidays 

Sounds good i will dig it out and check it is OK, you can have it for tests  

Cheers
Peter

[Itsu]

Nice work Itsu.

Grumpy is the Avalanche expert, we did quiet a bit with it at one point

I built a Marx Avalanche stack, add more stacks and you get higher voltage/ Energy dumped, very easy to build.

http://www.overunityresearch.com/index.php?topic=307.msg9605#msg9605

I have never tried driving a HHO cell but still have the electronics that i built  

Peter

Thanks Peter, 

lots of good info in that thread.     I will order some of those 2N5551, they are really cheap     (and some extra 2n2369's      )

Regards Itsu

[Itsu]

Itsu:

The local power supply bypass capacitor 0.1 uF shown on the schematic is an important part of the original circuit.

I don't see a local power supply bypass capacitor on your ground plane board. As it is now, your power supply leads will contribute some inductance, and you should not get a perfect pulse. This should be a good quality film type of 0.1 uF or tantalum may also work well or other low esr cap.

Scope ground leads will also have some inductance, so best to use a direct BNC to BNC connection to the scope.

Spiral trimmed resistors also could add some inductance to the output circuit. The output 50 ohm would best be a carbon slug rather than carbon film or metal film spiral trimmed types.

This may or may not improve the pulse, there are other variables. You might also try a short length of coax as the storage capacitor for a more square pulse.

Good tips ION   as always.

especially the  short length of coax as the storage capacitor  is a good one.


Regards Itsu

[Itsu]

Ok,  slowly getting there, using the groundplane pcb with the components shortly soldered to each other and as storage cap a 20cm long open ended piece of RG-316 coax cable.

And also very important...... remove the bandwidth limitation from the scope    

Closing in to the 1ns pulse width, see screenshot.


Still using the normal probe, when using a piece of 50 Ohm coax directly to the a scope port set to 50 Ohm shows an even smaller pulse, but the signal is to strong as in this 50 Ohm setting, the scope can only handle max. 5V RMS, so i need an attenuator.


Regards Itsu

[ion]

Itsu:

You can form a voltage divider as part of the 50 ohm load for the scope input and still use the direct BNC to BNC to the scope.

[Itsu]

ION, 


like changing the present one 56 Ohm emitter resistor to two resistors in series, one 47, the other 4.7 Ohm, and measuring across the 4.7 Ohm resistor?


Regards Itsu

[ion]

ION, 


like changing the present one 56 Ohm emitter resistor to two resistors in series, one 47, the other 4.7 Ohm, and measuring across the 4.7 Ohm resistor?


Regards Itsu

Yes, that should give you 11 times divider. A potentiometer in place of the 50 ohm would allow adjustment to exactly 10 to one or any divider ratio you choose.

Properly terminating the cable at each end would also be helpful. Right now the scope end is terminated in meg ohms. I sometimes use a tee coupler at the scope with a 50 ohm terminator inserted when working with a low impedance line to subdue reflections and standing waves.

[Grumpy]

Nice work Itsu.

Grumpy is the Avalanche expert, we did quiet a bit with it at one point

I built a Marx Avalanche stack, add more stacks and you get higher voltage/ Energy dumped, very easy to build.

http://www.overunityresearch.com/index.php?topic=307.msg9605#msg9605

I have never tried driving a HHO cell but still have the electronics that i built  

Peter

I'm not an expert, but I have built several avalanche stacks using the 2N5551's and other transistors and diodes.

I use the calculator at hyperphysics to generate resistor values for voltage dividers to scope the pulses.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/voldiv.html

I use metal oxide resistors mounted on a piece of acrylic or polyethylene sheet.

I have dividers for 1000:1, and 100:1

[Itsu]

Thanks for the info guys, i made a 10:1 voltage divider (47:4.7 Ohm) using carbon resistors and measure across the 4.7 Ohm resistor with a coax cable directly attached to the ch. 4,  set to 50 Ohm.

The coax cable storage cap was replaced by a high quality trimmer as the coax cable was very sensitive to the surroundings.

A pulse width of less then 1ns was achieved with rise and fall times around half a ns, see screenshot.

I guess still some improvement could be possible by using metal oxide resistors, using different transistors and/or putting the circuit in a shielded box with proper connectors

Video here:  https://www.youtube.com/watch?v=0_2Ea8_9o5k&feature=youtu.be


Regards Itsu

[poynt99]

 

[Grumpy]

what is Afro?

[Peterae]

G I have never noticed before, it looks like there is an error in the smiley set we use 
but i think we all know what a thumb up means 

[Itsu]

I received some 2n5551's, but they do not pulse in the circuit i used, see below.
I went up till 400V dc bias, but no pulse was seen.
Any idea why?

Regards Itsu

[MenofFather]

"...Any idea why this 2n2369 is so special in this case?
Any suggestions for an other (better) one...?"
Because it have frenquency 500 Mhz.
Better is mosfets, I think. And I think, that 50 ns pulse is good on 50 omhs load. Ruslan also say, that it have 50 ns pulse duration...

[MenofFather]

Itsu, that you get voltage of pulse in this picture?
http://www.overunityresearch.com/index.php?action=dlattach;topic=1556.0;attach=14738;image

[Itsu]

Hi menofFather,

yes, that pulse was made with my nanopulser using a 2n2369 transistor.
The amplitude (2.3V) is 1/11 of the real amplitude (28V) because i use a 1/10 voltage divider to measure this pulse.

Regards Itsu

[Itsu]

I made some improvements to the nanopulser and it now rightfully can be called a picopulser.
I used metal oxide resistors for the avalanche transistor base resistor and the emitter load/voltage divider resistors and put this avalanche part in a copper sheet box using proper bnc plugs.

Not sure why the negative pulse is so strong now (please compare with earlier screenshot above), most inductance should be gone.

When my BNC attenuator plugs arrive i could measure the real output for amplitude and width.

Video here:  https://www.youtube.com/watch?v=Vqgof8zgZZc&feature=youtu.be


Regards Itsu

[muDped]

Beautiful screenshot Itsu.

It exemplifies the extreme difficulty of getting
"clean" pulses at picoSecond pulse widths.

Even very tiny distributed capacitance and
inductance is able to form a resonant circuit
of sorts.  It is also possible that the metallic
circuit enclosure is beginning to operate as a
resonant cavity.

You're getting on up there in frequencies
approaching microwaves!

[Grumpy]

Nice to see avalanche pulses!

How are you setting the pulse width and what are you using for a load?

[Itsu]

Beautiful screenshot Itsu.

It exemplifies the extreme difficulty of getting
"clean" pulses at picoSecond pulse widths.

Even very tiny distributed capacitance and
inductance is able to form a resonant circuit
of sorts.  It is also possible that the metallic
circuit enclosure is beginning to operate as a
resonant cavity.



You're getting on up there in frequencies
approaching microwaves!

Thanks muDped,

yes, that copper sheet box could act as a wave guide, good observation.
How do i counteract that, i bigger box?

Regards Itsu

[Itsu]

Nice to see avalanche pulses!

How are you setting the pulse width and what are you using for a load?

The pulse width is set by the 2-7pF trimmer capacitor, but manipulating the load (here a 50 Ohm terminator plug) also has influence

The load at the time of the above screenshot was the 50 Ohm terminator plug.
But when using a 56 Ohm metal oxide resistor in series with a red led increased the pulse width / fall time to about 800ps producing a faint glow in the led.

(using the following pdf circuit on page 1108 as a guide:   http://academic.reed.edu/physics/courses/Physics332.s12/pdf/LED%20Luminescence%20Decay.pdf )
 
Regards Itsu

[ion]

Both ends of your BNC signal cable (scope end and driven end) should be terminated with 50 ohms or whatever the cable impedance is to prevent unwanted reflections and ringing.

The virtual open end at the scope is probably causing reflections.

This might require that your attenuator be re-arranged a bit, but not at all difficult to do.

The LED in series with the terminator resistor is not a good idea, as the line is virtually open until the threshold voltage is met, and definitely open in the reverse direction. The terminator impedance will drastically change with the series LED.