Stan Resonance finally cracked! by Sebosfato

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Just wanted to show you, the circuit stability now, the fast prototype board is ok the problem i was having was with a potentiometer...


all the chips are running at 5v excluding the driver witch is running at 12v...


I didn't finished the pulse indicator yet, now i'm going to perform some tests and when i have the transformer working i will than regulate the feedback....


I made some modifications on the schematics..


I'm using the lm741, the ca3040 is good also but for having 100% duty cycle the potentiometer and resistors must be rethink. Anyway is good also cause you can regulate better in higher frequencies..


ANyway i'm using the 741 cause it give me full range and i didn't had any 339 or 393 available...


The wave form i presented mean that i learned how to mix up the signals using the nor gates and the inhibit pin. Now I can select the number of pulses that go in each burst and the frequency and duration of the bursts... All this being this pulses in direct response to the antenna so being able to catch up any signal and follow it automatically sustaining the resonance.


As you can see now i have a mean to measure the frequency, i'm using a program called visual analyzer, and a netbook i had here.. As the computer is new the oscilloscope now works much better than in the other old shitty computer... 

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Seb,
Yeah I know, I was just breaking your chops out of frustration.  I wish you all the success and will be following along...


your frequency meter is a nice touch.

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Thanks for the energy input bro.


I'm finishing the connections here... last touches.


I repaired an old yellow multimeter i had here, so now i have two bad multimeters to measure too =)


I will add a 1kohm resistor across the primary.. .


Also i have a diode in series with the mosfet between the primary and the mosfet.


I think now is a question of hours...
 

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Almost ready to put it to work, oh boy much anxiety. Just woke up, cause today is gonna be a big day.

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Did some tests, the circuit now is not working, it is singing =)

Unfortunately i'm not able to measure many things the multimeters i have are so bad that even the voltage in the tx5 coil i'm not able to measure, i think the high frequency mess around with the numbers and they keep oscillating   from 1v to 25 to 58 back to 1... I'm only controlling the amperage input even that goes crazy some times but i'm keeping under 2 amps cause my variac is 0 .- 250v 2 amps rated... The mosfet is getting hot at higher voltages. I added a 1kohm resistor across the primary... I thinking about taking the capacitor i added between the drain and source...not sure.. 

The circuit works very nicely anyway, and it works by subtracting pulses without changing the frequency, is very interesting the sounds that come out of it. I was able to drive it in harmonics of the line frequency and the sound was nice too.

The circuit is working pretty stable as i told you... Hope to make it sing today.

i think that the capacitance is too small thats why is being a bit hard to resonate...

In my resonance experiments i used to use >1mh coil and capacitors like more than 30nf   this capacitance 300pf complicate the things... I think that if i had a big cell with more water and tubes inside the capacitance would be bigger and would be easier to resonate. I thinking about buying an acrylic tube but is very expensive here and i don't know yet where to find...

Now is all about tuning bros.

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The 2ohm resistor between ground and the source is affecting somehow like a negative feedback and maybe is causing the driver to not drive the fet into the enhanced mode and during the turn off the voltage can go negative turning on the mosfet again...


I'm going to initially try reducing the driver impedance by leaving only a 20ohm resistor with the backward diode over it..


Well for many problems must come better solutions..

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hello


more problems here, i got my igbt module burned when the fuse fused. The variac caused a spike that destructed the igbt. AT first i didn't understood why than i tried the other and pushed and the fuse blowed and the igbt was destructed...




Don't know what to do. This is not acceptable. I'm afraid i have to go to the electronic engineer university next week and see if i find some help.




I was going to try more but i don't want to burn more components. The main problem is that i don't have the money to burn and replace transistor after another until i find a good design.


I will enjoy the night winding more turns in the primary, thats all i can do... 

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Nothing like a night without sleep to find the ideas you need.


I think that i understood what is going on I think that the diode across the primary is a must have, cause it reduce the dV/dT transient, cause by the interruption of the current, If the diode is not there the "charged primary" will suck down electrons thru the capacitance between the drain and source charging the drain and source capacitance to up to double the supply voltage, and all this very fast. .


So i'm going to add a snubber circuit in the mosfet and across the primary, across the primary i will have a diode and some resistors, and across the drain and source there will be a capacitor and a diode with a series capacitor so we can discharge the drain source capacitance tension to change slower... I though about adding a 1nf capacitor and a diode with a 10k resistor in series...   


http://www.cde.com/tech/design.pdf


I though a way to protect against the fuse blow too, i'm going to add a capacitor and a resistor in parallel with the fuse so if it fuses it wont destroy the mosfet again...