Ok, a high pass filter in the white noise generator output, that would be the both Pic's, and that would make the white noise pink, right?
VioletIndeed, now the big resistor can be removed and 41V put directly on the drains and whalla, crackling noise emitted from the coils.
Interesting. I have to analyze whether the superposition of two noise waveforms can cause these amplitudes. My intuition says "no" but I haven't factored in the reflections from the ends of your "bifilar transmision line" yet.
I put 2 GDT (Gas Discharge tubes) of 230V across the drain/source of the MOSFETs, but they seem not to light up allthough i measure >400V peaks on the drains.
Turn off all the lights including scopes, tape up all pilot lights and put some camera on long exposure. I bet you will see these GDT light up.
My bench PS seems to have difficulty supplying current quick enough as the current limiter (10A) even when set to max. kicks in frequently, also
om the 30V circuit supply part 
We can't have that current limiter acting up like this.
Perhaps a large capacitor bank bypassing the output of the power supply will help. If not, add a huge choke between the caps and the power supply.
What is the " 30V circuit supply part" ? (I haven't been following closely).
First screenshot shows the signal across 1 MOSFET drain/source, the second screenshot is from across the 50 Ohm resistor on the main loop.
I saw them. Interesting.
What I am missing is the baseline at a different scale , i.e. V and I of normal noise pulses visible when the cracking is not occurring.
This is for comparison between the usual and unusual.
I won't repeat Peter's suggestions only add some more:
1) Null experiment: Does the crackling still happen wit a copper wire of the same diameter arranged on an identical coil former the same way? AFAIK you are using iron wire now...
2) Is the crackling sensitive to the static magnetic field of the permanent magnets (orientation, distance, plurality, polarization) ?
3) Is the signal at MOSFET gate disturbed by anything more than the Miller's capacitance (C
D-G) ?
4) Keep the scope probes away from the coil (only their tips should approach it). That might not be possible to notice easily with the randomness of the phenomena.
I will start by putting in >600V rated MOSFETs as these 200V IRFP260N's will not survive for long.
Stronger MOSFETs and drivers are a good idea. We do not want some avalanche D-S breakdown to be responsible for the crackling.
As usual, keep the Source-Gate loop
area as small as possible.
By the way, these crackling pulses on the drains are very small, <100ns, see screenshot.
That's good! Does the static magnetic field affect their width ?
The shear between two MOSFETs and the reflections from the ends of a transmission line (your coil) can interfere constructively or destructively....but that much!?
Do show a long flat line before the pulse. It is significant.
Author
Topic: Controller No5 With Protection - Looking for Explosions (Read 231554 times)
