And so it begins...

[moorejl57]

Tried a spice simulation. middle trace(fast coil, critical damped, avalanched) bottom trace(fast coil, overdamped, reduced Rd to eliminate avalanche) top trace(added capacitance to make slow coil, same Rd as bottom trace, critical damped, no avalanche) slow coil critical damped decays faster than fast coil overdamped with same Rd.

The LT Spice simulations look very interesting. I have used it in the past, but not for such a complex scenario, just a two pole LP filter for converting PWM to audio from a PIC. I will need to learn how to simulate simple front ends and targets, looks like a fun efficient way to test ideas.

[moorejl57]

Don't have a MPP so I'm guessing, looks like copper tape might be acting as a target. Not avalanching, maybe overdamped a little? Does the ringing damp out? How many micro seconds to damp out?

The hot lead insulation monitoring is a neat trick. I needed to add a thin layer of Kapton tape to the lead since the voltage seemed to be arcing through intermittently. As a test, I decreased the TX frequency to 250pps and increased the TX pulse width to about 300us and the spike trace still didn't get flat at the top, so I guess I am not able to force an avalanche condition with the combined 5.3ohm series resistance (3.3 + 2.0). I don't have ability right now to adjust the damping resistor, but is does look a little overdamped based on your examples. I will try some different values on Monday.

Below are the hot lead insulation spike at 300us and the TP3 signal that looks like ringing. It seems to be outside interference since it changes a lot by moving the coil.

[green]

One of the spice simulations I like playing with. Don't know what is causing the noise, I would start looking at the power supplies with the scope. Maybe someone else has a suggestion.

[moorejl57]

One of the spice simulations I like playing with. Don't know what is causing the noise, I would start looking at the power supplies with the scope. Maybe someone else has a suggestion.

Thank you for you help and suggestions. I will give the sim a look on Monday.

[moorejl57]

You get a direct ratio of the voltage IE: a 700 volt peak will give you 7 volts on the scope, so you dont blow your scope

The voltage divider method works brilliantly. I put two 10K in a breadboard and measured 1/2 of the flyback voltage at 216V after increasing TX pulse width to get the maximum. This confirms that the MOSFET is not going into avalanche given the max voltage of ~ 432V. This also puts me at ease knowing I am no exceeding the 300V input spec of my scope.

[6666]

The voltage divider method works brilliantly. I put two 10K in a breadboard and measured 1/2 of the flyback voltage at 216V after increasing TX pulse width to get the maximum. This confirms that the MOSFET is not going into avalanche given the max voltage of ~ 432V. This also puts me at ease knowing I am no exceeding the 300V input spec of my scope.

[ATTACH]46385[/ATTACH]

[green]

The hot lead insulation monitoring is a neat trick. I needed to add a thin layer of Kapton tape to the lead since the voltage seemed to be arcing through intermittently. As a test, I decreased the TX frequency to 250pps and increased the TX pulse width to about 300us and the spike trace still didn't get flat at the top, so I guess I am not able to force an avalanche condition with the combined 5.3ohm series resistance (3.3 + 2.0). I don't have ability right now to adjust the damping resistor, but is does look a little overdamped based on your examples. I will try some different values on Monday.

Below are the hot lead insulation spike at 300us and the TP3 signal that looks like ringing. It seems to be outside interference since it changes a lot by moving the coil.

[ATTACH]46382[/ATTACH] [ATTACH]46383[/ATTACH]

Some scope traces of my bench circuit. Not MPP, different gain and bandwidth. My scope trace with cfl bulb on looks same as yours, you get 5cycles/100us(50kHz). I recorded 50us/div and get 2.5cycles/div(50kHz). Wondering if a clf bulb is causing your noise. I calculate MPP amplifier should have about 25mvP-P noise with Rx input shorted. Wondering if you could measure with your scope sometime. Remove jumper Tx pin 2 to Rx pin 2 and jumper Rx pin 2 to Rx pin 3.

[moorejl57]

Some scope traces of my bench circuit. Not MPP, different gain and bandwidth. My scope trace with cfl bulb on looks same as yours, you get 5cycles/100us(50kHz). I recorded 50us/div and get 2.5cycles/div(50kHz). Wondering if a clf bulb is causing your noise. I calculate MPP amplifier should have about 25mvP-P noise with Rx input shorted. Wondering if you could measure with your scope sometime. Remove jumper Tx pin 2 to Rx pin 2 and jumper Rx pin 2 to Rx pin 3.

Thanks for the info and analysis. I am in a veritable sea of CLF and LED lighting and I measured it at 50 kHz as well, good detective work

[moorejl57]

I succumbed to 3DSS coil fever and made a attempt at making a coil based on the howto instructions. I made a 3D printed form and started winding. Unfortunately, I got distracted by my wife around layer 4 and kind of lost count. Sadly, it only measures at 40uH lol. In any case, I have a good understanding of how to make one. I attached the stl and gcode files for anyone would like to try printing the form.

Basket Coil Form 195mm.zip

[6666]

BIG THANKS FOR STL FILE, I am printing it now on my crappy ender 3, this is the biggest print I have done so will very interesting to see how it comes out

[moorejl57]

BIG THANKS FOR STL FILE, I am printing it now on my crappy ender 3, this is the biggest print I have done so will very interesting to see how it comes out

Should work good, the ender is a Prusa clone and I printed on a Prusa MK3. The slots are 2mm by 4mm, so if your wire dia requires longer slots, I can post a modified stl.

[6666]

Should work good, the ender is a Prusa clone and I printed on a Prusa MK3. The slots are 2mm by 4mm, so if your wire dia requires longer slots, I can post a modified stl.

Thanks for the offer would it be possible to have a stl with longer slots PLEASE ?
what software do you use ?

[moorejl57]

Thanks for the offer would it be possible to have a stl with longer slots PLEASE ?
what software do you use ?

I use OnShape: https://cad.onshape.com/documents/e4...0d237219a2b305

All you have to do is copy and open the document online and edit the length of the dimension slots, then export as stl.

Coil Form 5mm Slot.zip

[6666]

Thanks for the new file, will print it to, just waiting for last print to cool down looks good
is onshape a pay only site ?

[moorejl57]

It's free for a public account and is easy to learn.