good going Bryan

If you find even a little choke that uses a ferrite core, you might be lucky and
get the sort of result I got (a straight line then increasing steepness).
Don't worry if your results look different to mine.

Ferrite cores are way different to the very thin laminated Iron core that you are testing now.

I just tested a large Aerosharp choke with 6 turns.
the current curve looks just like yours.
The Purple trace is voltage and it drops 3 volts, down from the 12V start point
during the pulse.

Well decided against taking the choke out of my inverter as down the track I will be building another Madboard and they can be tested then.

Awhile I played with one of those Temu induction heaters where I did manage to let the magic smoke out with my copper coil mod's  

Anyway decided back then to build my own which became one of those projects to finish and went into somewhere in the shed  

Found the toroid I made for the project so decided to give it a test.





This is the 210us pulse which works out to 10.5uf and 240A





The 310us pulse which works out to 12.45uf and 300A




The 400us pulse which drops to 2.4uf and 205A



So may be time to get the second one made and revisit this project.

Regards Bryan

It looks like your capacitor bank is running out of charge after 50µS with such a low inductance.
To get a better look at what that inductor is doing perhaps reduce the pulse width to 50µS and set the scope time base to 10 or 20µS/Div.
Edited 2026-07-01 12:01 by phil99

Rather than use this thread for my testing it may be better to start a new thread for this Induction Tester.

I have in my build notes a comment by Poida that if the input voltage is going to be more than 85V, R6 should be changed from 2K7 to 1K5 or 1K. Does this mean that if I do so, I should no longer operate at 85V? ie., should R6 be no greater than 1K5?

R6 appears to part of a voltage divider for measuring the Solar array voltage.

If your solar voltage is above 85V, change the value to 1k5, or you may need 1k if the voltage even higher.

If the resistor value is incorrect, you won't be able to adjust/calibrate the Solar voltage setting in the menu for the correct solar input voltage.

Ideally you want to be able to see the VOC "open circuit voltage" on the LCD.

Look up the VOC data for the panel, add them together for each series panel, two panels in series will likely be between 72v and 98v VOC.

If unsure, fit a 1k and see if you can calibrate the menu setting to display the correct voltage.

I'm sure someone who has one of these running will help with the values they used for their solar panel voltage.
.
Edited 2026-07-08 14:01 by KeepIS