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Hello to all reading this, I am writing this in good faith and it may even be right (well almost)
Regarding building a Surf PI 1.2 kit, winding a coil and getting nothing or poor results. Everything is starting to become clear, it seems that although the PCB is supplied with a 390R and the original Whites Surf PI uses a 360R, “you don’t want to use that” because it is to damp a specific coil (your very special individual coil, that you make for the kit will not match it, (it may however be very close), and once that the damping resistor is set somewhere between 150R and 1K with a scope attached and I have done that (my own coil wanted about 610R as the result) things will be better.
The info I picked up from help within the forum was to build a damping setup unit using two fixed resistors and a pot ("10k pot and a 200R in series" then paralleled with a 1K2) so the swing will be between 170R to 1K1 or thereabouts. Use a scope and monitor the ringing at the offset test point, make or fit a value both for R and W that is close to the tester value.
Wait we are still not out of the woods there is the delay to set and if it is too slow it will fail to run and if it is to fast it fails too. So another happy medium to find. There may be a scope point but where that is I do not know or I missed it, there is little information about, but someone knows.
I do hope this gets someone out of a hole as I have been in mine for a while.
One final point and that is; if you want to use another coil size, material, turns etc. you will need to re-tune the damping resistor and that explains why I have a box with several coils in it that appeared not to work.
What I would like to read is what others have done to get the best depth readings.
Regards.
Regarding building a Surf PI 1.2 kit, winding a coil and getting nothing or poor results. Everything is starting to become clear, it seems that although the PCB is supplied with a 390R and the original Whites Surf PI uses a 360R, “you don’t want to use that” because it is to damp a specific coil (your very special individual coil, that you make for the kit will not match it, (it may however be very close), and once that the damping resistor is set somewhere between 150R and 1K with a scope attached and I have done that (my own coil wanted about 610R as the result) things will be better.
The info I picked up from help within the forum was to build a damping setup unit using two fixed resistors and a pot ("10k pot and a 200R in series" then paralleled with a 1K2) so the swing will be between 170R to 1K1 or thereabouts. Use a scope and monitor the ringing at the offset test point, make or fit a value both for R and W that is close to the tester value.
Wait we are still not out of the woods there is the delay to set and if it is too slow it will fail to run and if it is to fast it fails too. So another happy medium to find. There may be a scope point but where that is I do not know or I missed it, there is little information about, but someone knows.
I do hope this gets someone out of a hole as I have been in mine for a while.
One final point and that is; if you want to use another coil size, material, turns etc. you will need to re-tune the damping resistor and that explains why I have a box with several coils in it that appeared not to work.
What I would like to read is what others have done to get the best depth readings.
Regards.
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