Costinbuc's Ideas and Experiments

Hi Costinbuc,

It's okay, I see it now. Sorry, I thought it's missing.

About the +19.6 V, that is normal, it's the effect of the coil.

If you'll play with the frequency and duty-cycle from the signal generator you should be able to find the resonance frequency of your coil where Vpp (voltage point-to-point, your scope could display that too) will be at maximum and the waveform will show your coil is "ringing".

Take a look to my post here, I'm using 42.9 V very short pulses (duty-cycle set to 1%) as input and at its resonant frequency my coil is showing a "ringing" waveform with Vmax=460V, Vmin=-392V and Vpp=852V:

So the first thing is to set your scope to show the Vpp just like it's showing the other parameters now (Vmax, Vmin, Freq).

After that you need to find the resonant frequency of your coil, the matching frequency and duty-cycle on your signal generator where Vpp is at maximum. 

Then you'll see your scope will show a "ringing" waveform like in the image above and I'm pretty sure the Vmax will be much higher.

And as a note, no matter what coil you will be using, be careful that too high Vpp could destroy your protection diode. Its purpose is to protect the rest of your circuit against the BEMF (back electromagnetic field) produced by the coil. If the Vpp is too high (meaning the BEMF is too high too) your protection diode will not be able to handle it anymore and will break.

But for now I think the diode is safe, as you can see in my image above I have Vpp=852V and my protection diode is fine.

No worries, you'll learn all these things by experimenting, looking on internet for the meaning of the terms we're using here and when it's something not clear asking here to our team members which are very experienced and very advanced in electronics and physics. 

That's how I learned (and I'm still learning) too. Just like I did, sometimes during the experiments you'll break some components (diodes, MOSFETs, etc.), that's fine - it's a part of the learning process and understanding the devices we're experimenting with. If you'd know how many diodes and MOSFETs (some very expensive like the Cree MOSFETs) I broke during my experiments... 😁

Regards,

Fighter