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Just been playing with the MPP and found an interesting issue. With the TX period set to 1khz (1000us), I get some sort of harmonic that creates a click noise in the speaker every 1 sec. If I change the period to say 800us or up to 1200us, the click disappears. Must be something in the workshop causing it. Our mains freq is 50hz so it may have something to do with that.
This is with original MPP specs (TX width, sample width etc) as well as other timings I have been playing with.
Another thing I have done as an experiment is to add cc circuitry ( only 2 components) and limit coil current to just over 1A. It achieves full current in approx. 26us. It doesnt appear to have made any difference to detection depth (air tests in workshop) but allows the FET to run a little cooler.
This is with original MPP specs (TX width, sample width etc) as well as other timings I have been playing with.
Another thing I have done as an experiment is to add cc circuitry ( only 2 components) and limit coil current to just over 1A. It achieves full current in approx. 26us. It doesnt appear to have made any difference to detection depth (air tests in workshop) but allows the FET to run a little cooler.