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Hi Guys, asking for help again!!!! I'm still struggling with my Surf PI 1.2 long board.It still seems low sensitivity to me,.. I have sorted out the R18 / R20 problem, (before that I could only detect a 2p to 2",... I can now spot it at 5" max... :-(
I've run a 'scope round a few points, trouble is, I dont know what should be where, (it is my first build, Guys!) I'll tell you what I have, & where, does anything seem out of order????
First off, the FET is running at roughly 615Hz, with an 'on' time of 57 microsecs,.. I guess this is about right??? Flyback pulse measures at 164V spike, which probably is not far off, either??
OK, the rise time seems fast, it gets back to 0V after 7 to 8 microsecs,... the sample pulse timing is adjustable with the delay pot, of course,.. the sample pulse on output of 14093 [pin 3, U4A] is about 40 microsecs wide, and the closest i can get it to the negative fall of the flyback pulse is 40 (ish) microsecs,... and the detector stops working when it gets closer than 42 Microsecs, or so.
does the above seem right??? I have tried a 390, 470, and 560 ohm damping resistor,.. coils ( I have wound 3) are a mix of straight coil, 22 turns, 10", 300 micro henry, and 'basketweave' types, same size, slightly less inductance. All give same sensitivity results. I have tried detector on a 12V Sealed lead acid 2Ah battery, and 2 different 11.1V Lipo's from my R/C heli's, same results.Can anyone with a Surf PI longboard tell me if any of the above are right, or wildy wrong????
Offset pot has set the opamp output at 0V, and 'tune' pot seems to do as it should, I set it to just start to 'burble' audio into the headphones....
I feel the sample is sampling a virtually 'flat' bit of the waveform, but is it because the sample is too late, or because the rise time is too fast, or are they about right, and I have a problem elsewhere???
TIA for any input, Cheers, Fred
I've run a 'scope round a few points, trouble is, I dont know what should be where, (it is my first build, Guys!) I'll tell you what I have, & where, does anything seem out of order????
First off, the FET is running at roughly 615Hz, with an 'on' time of 57 microsecs,.. I guess this is about right??? Flyback pulse measures at 164V spike, which probably is not far off, either??
OK, the rise time seems fast, it gets back to 0V after 7 to 8 microsecs,... the sample pulse timing is adjustable with the delay pot, of course,.. the sample pulse on output of 14093 [pin 3, U4A] is about 40 microsecs wide, and the closest i can get it to the negative fall of the flyback pulse is 40 (ish) microsecs,... and the detector stops working when it gets closer than 42 Microsecs, or so.
does the above seem right??? I have tried a 390, 470, and 560 ohm damping resistor,.. coils ( I have wound 3) are a mix of straight coil, 22 turns, 10", 300 micro henry, and 'basketweave' types, same size, slightly less inductance. All give same sensitivity results. I have tried detector on a 12V Sealed lead acid 2Ah battery, and 2 different 11.1V Lipo's from my R/C heli's, same results.Can anyone with a Surf PI longboard tell me if any of the above are right, or wildy wrong????
Offset pot has set the opamp output at 0V, and 'tune' pot seems to do as it should, I set it to just start to 'burble' audio into the headphones....
I feel the sample is sampling a virtually 'flat' bit of the waveform, but is it because the sample is too late, or because the rise time is too fast, or are they about right, and I have a problem elsewhere???
TIA for any input, Cheers, Fred
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