Getting ready to build the MPP

[baum7154]

Best of luck on your coil build!
If you have not already done so, take a look at the COILS forum 'CHANCE PI COIL' thread as it is the original source of build info and development of these '3DSS' (3 Dimensional winding pattern/Self Shielding) type of coils derived from a very old crystal radio antenna of the 1930's.

Dan

[KRinAZ]

Thanks Dan, I will built a coil with the recommended wire in the same way Kyle did and see if it makes a difference. Defenitely worth trying.

I agree with Dan, the thicker 600V PTFE wire jacket makes a big difference in reducing capacitance. I would also add that I have discovered some wire manufacturers (e.g. Phoenix Wire & Cable) have different thicknesses for 600V wire - Phoenix has 3 different thicknesses for a given AWG size all for 600V rating - so you may want to watch for the jacket thickness. Good luck with your coil build! As Dan suggested the Chance PI Coil forum is an excellent resource for buildind 3DSS coils - it's how I got started...

[KRinAZ]

--------------------------------------Looking at the AWG tables... going to 24awg will give about a 37% reduction in resistance. 22awg will give about a 60% reduction in resistance compared to 26awg. Keep in mind that the larger gauges will increase interwinding capacitance in the coil and twisted feed, increase weight, increase eddy currents, and fill the slots of the coil form more quickly.That said, I believe 24awg is the best wire choice in optimization of my 3DSS monocoils.Regarding the audio response between lead/gold and copper jacketed bullets they are unmistakeable on the CHANCE PI too. The longer copper jacket response of the bullet easily overwhelms the short response of lead or gold bits.Good luck!Dan

OK thanks for that info Dan, I may try 22AWG & see if the tradeoff between the lower resistance & higher interwinding capacitance makes a good balance. I will still be over 1 ohm though (I'm estimating the resistance will be 1.28 ohms) & I still wonder how Minelab & Coiltek manage to build their coils with sub 1 ohm resistance & yet keep their capacitance very low...still 1.28 ohms is a big improvement over 3.2 ohms...

[localbug]

Adding a resistor in parallel to lower the resistance and add a capacitor in series to lower capitance of a coil. Will it work that way??

[CAS]

Adding a resistor in parallel to lower the resistance and add a capacitor in series to lower capitance of a coil. Will it work that way??

Unfortunately no. The internal resistance and capacitance of the coil create an inductive and capacitive reactance within the coil which cant be altered by external components.

[homefire]

Short Long Story. Yes a outside circuit would see the coil as you describe but for our purposes the coil would still be acting as it truly is.

[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.

[WM6]

Hi Quiaozhi

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

What is your proposed two coil MPP circuit solution?

[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.

[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.

[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]

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]

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

[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]

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 ?