Getting ready to build the MPP

[KRinAZ]

To rehash the template discussions, seems like pretty much everyone has run into problems with the wire slot width, in my case the inner slots becoming filled faster than the outer. I will make a revised version of the template with the inner slots at .55" depth, leaving the outer slots as they are at .4" depth - as on my builds the outers are still anchored well where the inners are just past their limit - I believe this should yield a coil that is equally balanced for anchoring on inner and outer slots.

The next set of templates will be hopefully posted this eve...

[KRinAZ]

Hi KRinAZ, do you have a plan for a coil housing for your new oval coil? I haven't worked with Lexan. Do you think it would work for a housing?
Hey Chet, yes, I do have a plan! I've discussed this coil with Don Bowers and suggested that if a number of us build these coils and would like a housing he could make housings for us. Currently it looks like the housing would be about 8.25" x 10.25" x 1", could be any mount we all agree on (he usually uses the 19mm Whites/Tesoro/Minelab mount tabs unless otherwise specified) We will need to get the cost per housing from him when we are ready, it appears they would be around $15 each (US Dollars) - price seems good to me!
On the Lexan, it seems to be pretty heat resistant and not as well suited to heat/vacuum forming as ABS. Don uses ABS sheets, can be either black or white, I'm told black is UV resistant, white is not.

If we have some made I can make a cool graphic to stick on top of it! Name for the coil, anyone?

.

[KRinAZ]

I have an idea for name - more practical than flashy - BWM800 and BWM810 for Basket Weave Mono 8" & 8"x10", can put the flashy in the graphics...folks like SharpDots.com (I have no affiliation with them) and maybe even the local office supply stores with business printing capability can I believe make stick on vinyl decals from an image...

[KRinAZ]

Question on that high speed, high voltage diode used to lower TX circuit resonant frequency - if someone didn't have any diodes on hand and was going to get some diodes specifically for this - would the MUR460 be recommended or is there another diode that would be even better/faster?

[Silver Dollar]

BWM800 and BWM810 for Basket Weave Mono 8" & 8"x10",

I got the shoes;

I would a 10" coil with the Litz tonight. I'll test it out tomorrow or Saturday..


I found some MUR460's in old TV sets. I'm planning on using those...

[johnandles]

I have an idea for name - more practical than flashy ...... I believe make stick on vinyl decals from an image...

OB1 (oval basket 1)...may the force be with you...
lol

[KRinAZ]

OB1 (oval basket 1)...may the force be with you...
lol
Haha that's good!

.

[KRinAZ]

I got the shoes; [ATTACH]31595[/ATTACH]
How 'bout the car/motorcycle to match lol?

I would a 10" coil with the Litz tonight. I'll test it out tomorrow or Saturday..
[ATTACH]31596[/ATTACH]
Cool, interested in it's specs & how it performs

I found some MUR460's in old TV sets. I'm planning on using those...
Hmmm, good tip...maybe I should pickup some old TV's - they're free on craigslist...

.

[KRinAZ]

On post #76, "...seems like pretty much everyone has run into problems with the wire slot width..." I meant wire slot depth. The wire slot width of 1/8" seems fine...

[KRinAZ]

OB1 (oval basket 1)...may the force be with you...
lol
and may the Schwarz be with you

.

[KRinAZ]

Interesting note on Step 6 - I am able to adjust the main sample delay (the pulse on TP5) down to a minimum of 5.25uS - cool! Now, for a TX circuit & coil that fast!...

I set it back to 20uS for now to be able to follow the build doc. Once MPP is operational I will go right to the mods and this will be set to probably 7.5uS

[KRinAZ]

Well I'm having a problem with Step 8 - Second Integrator. Build manual says I should see a +5 to -5 VDC swing at TP9 as I turn the threshold pot. I get a +.017 to -.017 VDC swing (on my scope). The build doc says I should see a voltage change when a target is near but I see no change.

Step 7 went fine and I have a nice voltage increase at TP4 (which feeds into the Second Integrator) with target near coil.

I verified all the resistor values and ohm'd the circuit and no shorts, all resistances what they should be. I verified C15 & C18 are good, no shorts, and they are the right value (with my meter). I do have a +5 to -5 VDC swing at the middle pin of the threshold pot as I turn the pot.

TP 9 looks the same whether U9 (TL071)(which drives TP9) is in or out of the circuit. Made sure + & - VCC at pins 4 & 7 of U9 are good.

I checked everything I can think of, it's as if U9 is dead. It couldn't be, right!?! Of course I don't have another to swap with it - would have to get one online (unless someone knows some gear that usually has them that I can rob).

Anyone know of a way to verify the TL071 is functional (other than swapping it)?

Otherwise, if anyone has something I should check or other ideas I would sure love to hear them! Guess I'm stuck right here...

[KRinAZ]

I have updated the basket weave coil templates for the increase in the inner wire slot depths from .4" to .55" to balance the wire anchoring in the slots. I have also added a version number to the templates in the lower right corner so you can know if you have the latest. The latest 8"x10" elliptical is v5, the latest 8" round is v2.

8 inch Coil Form v2.pdf
8" Round v2
8x10 Coil Form v5.pdf
8"x10" Ellipse v5

These are intended to be used with 32 turns (6 layers + 2 turns) (or less) of wire with OD up to 1.5mm, yielding about 324uH and around 3 ohms at 32 turns, depending on the wire you use. Smaller OD wire will allow even more turns and higher inductance.

As always, let me know if you discover any issues with these templates, and enjoy!

[green]

[ I get a +.017 to -.017 VDC swing (on my scope).]

I calculate .17 volts with U9 removed. If you are getting .017 I would keep looking.

[Qiaozhi]

Well I'm having a problem with Step 8 - Second Integrator. Build manual says I should see a +5 to -5 VDC swing at TP9 as I turn the threshold pot. I get a +.017 to -.017 VDC swing (on my scope).

The voltage swing at TP9 should be [more or less] +/-5V as you adjust the Audio (threshold) pot.