Getting ready to build the MPP

[Tibuck19]

Can someone explain how to test coil using this scope

https://www.youtube.com/watch?v=PXoKiEQ8qOY

[paku]

Can someone explain how to test coil using this scope

[Tibuck19]

The external Reject pot adjusts the main sample delay (TP5), and R6 sets the minimum value. If the Reject pot is set to zero, then R6 * C8 (100k * 220pF) = 22us. This is the maximum value possible for the minimum main sample delay.

The EFE sample delay (TP6) is set by R10 and C10. So R10 * C10 (10k * 10nF) = 100us.

The main sample (TP7) and EFE sample (TP8 ) pulse widths both need to be the same width, and are set by R11 and C11. In this case (due to the presence of D4 and D7) the pulse widths will be approximately R11 * C11 (22k * 2n2) = 48.4us.

None of the above are affected by whatever values you choose for R7 and R8.

Thank you once again. I learn quickly but I need to be re told often Kinda like a Dalmatian lol

[Qiaozhi]

Going back to the ref documentation, Main and pules widths EFE R11 on tp5 and tp7 it says MSD of 22us and, secondary EFE pulse R10 Tp6 and Tp8 at 100us and 58us, should they be those values regardless of how R7 and r8 values are ? hens the frequency I believe?

The external Reject pot adjusts the main sample delay (TP5), and R6 sets the minimum value. If the Reject pot is set to zero, then R6 * C8 (100k * 220pF) = 22us. This is the maximum value possible for the minimum main sample delay.

The EFE sample delay (TP6) is set by R10 and C10. So R10 * C10 (10k * 10nF) = 100us.

The main sample (TP7) and EFE sample (TP8 ) pulse widths both need to be the same width, and are set by R11 and C11. In this case (due to the presence of D4 and D7) the pulse widths will be approximately R11 * C11 (22k * 2n2) = 48.4us.

None of the above are affected by whatever values you choose for R7 and R8.

[Tibuck19]

Going back to the ref documentation, Main and pules widths EFE R11 on tp5 and tp7 it says MSD of 22us and, secondary EFE pulse R10 Tp6 and Tp8 at 100us and 58us, should they be those values regardless of how R7 and r8 values are ? hens the frequency I believe?

Update : I set them to those Values as stated in the Ref Manual and it seems to have solved the EFE coil bounce problem and I am still getting Good detection. But nonetheless is that the correct way of setting it up with the mod ? also worth noting, before I added Tripots to R7 R8 R10 and R11 with my working coil, I went from damping resistor value of, 660R to 480R to now 380R none of which were over damped at first till tweaking , if any has the patents to explain this to me, I would appreciate the knowledge

[Tibuck19]

When I tweak R10 and R11 which TP do I use and is the goal to set it at 0V something like the offset of the Surf Pi ?? I am getting good detection depth however EE is a problem now when I wave a magnet over the coil or swing the coil itself. do I increase or decrease the values ?

Going back to the ref documentation, Main and pules widths EFE R11 on tp5 and tp7 it says MSD of 22us and, secondary EFE pulse R10 Tp6 and Tp8 at 100us and 58us, should they be those values regardless of how R7 and r8 values are ? hens the frequency I believe?

[Tibuck19]

R10 adjusts the secondary (EFE) pulse delay, and R11 adjusts both the main and EFE sample pulse widths.
The signal at TP3 looks underdamped. Changing R10 and/or R11 should have no effect on this. You probably just need to tweak your damping resistor value.

When I tweak R10 and R11 which TP do I use and is the goal to set it at 0V something like the offset of the Surf Pi ?? I am getting good detection depth however EE is a problem now when I wave a magnet over the coil or swing the coil itself. do I increase or decrease the values ?

[WM6]

I've tested the balanced coil configuration using a Garrett Infinium LS Power DD coil.
The wiring details for a balanced coil is shown on page 14 of the Build Document.
For the Garrett coil it was only necessary to add a damping resistor on the TX winding, and I was able to sample at sub 10us.

Thanks Qiaozhi.
Need to put another look at Build Document.

[Tibuck19]

If you've changed R7 and R8, then you will have affected the parameters of the TX oscillator. This will quite likely mean that the damping resistor needs adjustment, especially if it was on the edge of being underdamped.

Perhaps so, They are still the same values and set to the same resistance as the others were but perhaps being different manufactures it maybe enough to cause it the first ones were recycled button pots and the new ones are bourns style from china of course . we will find out, I'll pull the Damping resister and tweak the value with my Damping-pot. Thanks for your advice and ill let u know how it works out. EDIT: Good call lol your the man! it was indeed the damping resistor ,Thank you

[Qiaozhi]

That's what's odd about , it's the same coil, with the same Damping resistor. I used to set it up the first time around, I've used the detector all summer long. the only changes I did since then was replacing the ( 5K R7 and a 40K R8 changed the first trimmers I originally put in, for new ones) and added trimmers to R10 and R11. Is it possible the bent over leg of the trimmer on R7 is touching R2 or perhaps R1 ? I did feel like a tight fit and its set in a little crooked.

If you've changed R7 and R8, then you will have affected the parameters of the TX oscillator. This will quite likely mean that the damping resistor needs adjustment, especially if it was on the edge of being underdamped.

[Tibuck19]

R10 adjusts the secondary (EFE) pulse delay, and R11 adjusts both the main and EFE sample pulse widths.
The signal at TP3 looks underdamped. Changing R10 and/or R11 should have no effect on this. You probably just need to tweak your damping resistor value.

That's what's odd about , it's the same coil, with the same Damping resistor. I used to set it up the first time around, I've used the detector all summer long. the only changes I did since then was replacing the ( 5K R7 and a 40K R8 changed the first trimmers I originally put in, for new ones) and added trimmers to R10 and R11. Is it possible the bent over leg of the trimmer on R7 is touching R2 or perhaps R1 ? I did feel like a tight fit and its set in a little crooked.

[Qiaozhi]

Hi Quiaozhi

Did you experiment with two coils (TX & RX) with MPP too?

What is your proposed two coil MPP circuit solution?

I've tested the balanced coil configuration using a Garrett Infinium LS Power DD coil.
The wiring details for a balanced coil is shown on page 14 of the Build Document.
For the Garrett coil it was only necessary to add a damping resistor on the TX winding, and I was able to sample at sub 10us.

[Qiaozhi]

Can someone help me out, I replaced R10 and R11 with trimpots and R29 with a pot what TP do I use to adjust the Sample pulse width and EFE (secondary) delay on? I fitted the trimpot as shown in the little drawing, is that how we replace resistors with trimmers? also something odd with TP3 the waveform it is not what it use to be, if anyone has an idea why? Everything still works I'm getting good detection still.

[ATTACH]42416[/ATTACH]

[ATTACH]42417[/ATTACH]

R10 adjusts the secondary (EFE) pulse delay, and R11 adjusts both the main and EFE sample pulse widths.
The signal at TP3 looks underdamped. Changing R10 and/or R11 should have no effect on this. You probably just need to tweak your damping resistor value.

[WM6]

Hi Quiaozhi

Did you experiment with two coils (TX & RX) with MPP too?

What is your proposed two coil MPP circuit solution?

[Tibuck19]

Can someone help me out, I replaced R10 and R11 with trimpots and R29 with a pot what TP do I use to adjust the Sample pulse width and EFE (secondary) delay on? I fitted the trimpot as shown in the little drawing, is that how we replace resistors with trimmers? also something odd with TP3 the waveform it is not what it use to be, if anyone has an idea why? Everything still works I'm getting good detection still.