In The Ever lasting Chain Of Experiments The Next Project, ultrasonic anti-fouling for boats.
Part 11, dry testing
Made a small test-board (PIC out of programmer now), and wound a test transformer. This one is way too small (the EI core is still on its way), so .. expected problems.
The one I found in the junkbox already had the secondary, looked like some more turns than I needed, but anyways, connected it, and that ozone smell, OK, turn voltage down, pile of smoke.
Removed secondary winding, must have a been a thousand turns or so, was the one I used to test some PMT HV for 2 kV.. well, say 2000 turns, only needed 120 for this test, so got about 11 kV, OK that enamel isolation you know.
The primary was difficult as it would not fit, settled for 2 x 6 turns. wound the 120 turns secondary:
Already wound the 1:50 current transformer, you can see it here at the bottom of the board (ringcore), for cycle by cycle current limiting using the PIC comparator, works great:
Managed to put 600 Vpp into the transducer at 20 kHz...
and that does not even take much power:
Will be even better with the right transformer and correct waveform...
But when I left the room for the kitchen to give myself a cookie for work well done, I could still hear that high pitched noise although I switched it off.
Note that the MOSFETs are not on a heatsink, those stay cold, just a few mOhm on. PIC has no problem whatsoever to drive these, even with the 5.6V zeners on the gate as protection. Tronix for the day.
Still hear that pitch.... Next time earplugs? Or does it come through the skull?