MMP saga continues

[Tibuck19]

That's the problem ... "hooked to a bench power supply".
If your scope and the bench power supply both have their common line connected to mains Earth, then they're shorted together. Since the MPP uses battery positive as 0V, you are shorting the supply lines via earth.
I've just checked continuity from my scope's ground to earth, and there's a connection (as expected), but my my bench power supply has outputs that are isolated from earth. Therefore I am able to use my scope on the MPP with a bench supply.
So, either connect your MPP to a battery pack, or buy a better bench supply, and the problem should go away.

That was indeed the problem also if Homefire and yourself remembers the Noise on the tail end of the Oscope reading , it was also cause by noise in the power supply .
With power Supply


With battery pack.

[homefire]

Cool.

[Tibuck19]

Not built it as of this time . Have two PCB and all parts set up to go. I would try a basket coil on that thing. This is a 5" I'm playing with for the Barracuda. Pretty much same requirements.

5 inch form
24 SWG copper
Unknown Turns
410uH
1.4 Ohms


[ATTACH]39970[/ATTACH][ATTACH]39971[/ATTACH]

After changing that Bad 555ic and the bad 78L05 which got the MMP working well again, I started to re-visit a 6" spider coil I had started a while back ago, I think the rule of thumb of width = depth applies, im getting a Good whisper at 8 inches and a very solid signal at 6 inches on all Canadian and American coins and the some on a 1906 usd V nickel lol my best find to date but depth doesn't change, coins to a big pair of scissors and pliers Does that seem right to you guys? . I think its going to make a good trashy area coil pin pointing with it seems to be really good , im printing the coil housing and other parts now So in 10 hours or so lol I might have a fully finish coil to test.

[homefire]

Tried a Spider type like that with unimpressive results. The Stacked type works quite a bit better for depth.

[Tibuck19]

Tried a Spider type like that with unimpressive results. The Stacked type works quite a bit better for depth. [ATTACH]39987[/ATTACH]

What is the depth are you getting ? Does that kind of coil need shielding ? or because it made with 22-26 gauge wire it doesn't need like mono loops don't?

[homefire]

Yes shield is still needed for Ground Signal. Only way is Graphite in housing. No big deal. With this 5" the Barracuda running about 15uSec Delay sings at 7"-8" on a Nickel most well. I'm looking for less then 10uSec delay on my MMP build.

This one:
2 x 24guage
10 turns
5inch form
1.4 Ohm
420uH

[Tibuck19]

Yes shield is still needed for Ground Signal. Only way is Graphite in housing. No big deal. With this 5" the Barracuda running about 15uSec Delay sings at 7"-8" on a Nickel most well. I'm looking for less then 10uSec delay on my MMP build.

This one:
2 x 24guage
10 turns
5inch form
1.4 Ohm
420uH

[ATTACH]39988[/ATTACH][ATTACH]39989[/ATTACH]

That does look nice indeed I finally finish that coil I was talking about , after putting the minipulse back in its case and hooking up the headphones I can say for sure at 9 inches everything from a USA and Canadian penny to a toonie is a clear signal and Really beeps in hard at 6.5 inch, but from 6.5 to 9 inches you can defiantly hear there is something there. Also there is no false beeping without coil shielding, when coil is swung. I must say it will be handy in a park I like to go , its full of targets and with my 10Inch I end up digging 8 inch wide holes lol this one is very pin pointing capable. If anyone wants the STL to print their own , I am more then happy to share the files.

[homefire]

What Size is that shell? I assume they can be scaled up or down in size some what ?

[Tibuck19]

What Size is that shell? I assume they can be scaled up or down in size some what ?

You mean coil housing ? it is 185mm X 185 mm 16mm high, yes it can scales up to any size you would need by modifying the cad, but anything pass this size has to be cut to fit the printer bed dimensions which most printers is 200mm X 200, but that is not a problem ,1/2 or 1/4 parts are easy to glue back with abs mix and joints are easily sanded away

[Tibuck19]

What Size is that shell? I assume they can be scaled up or down in size some what ?

keep the Homefire buring lol I had a thought , If you look at the photo's you will see because of the spider coil "bobbin" I had to use more resin to fill which makes it heavier, But in you case if you take a Top photo and give me the distance of opposing points And total height, I can use it as a reference in the cad software , maybe I could find spots to made bigger cavities to cut back on the amount of resin hens cutting back on weight.

[homefire]

Actually that's exactly what the Handle is about. At one time it was Homefires ! The walls on your housing look quite thick. Could it be done thinner or would that cause issues ?

[Tibuck19]

They are only 2.8MM thick they could be shaved 2mm with out much issue, but I like having a nice Curve Aka Fillet to the top and you need some thickness to pull it off, I do chamfer the inside which adds some thinkness in the joints, but with this coil I couldn't really do it, but trust me its not the extra 0.8 mm that adds a lot weight, the abs is rather a light material. nonetheless, in theory, it could be done with two passes of a normal nozzle which is 0.4 making it a 0.8 wall, but the problem would be with the heat generated from the curing stage of the resin, it would surely warp a thin wall of 0.8mm , I always made the coils this way and I haven't broke one yet, I bang them around in rocks when detecting on riversides. lol the old saying if it an t broke don't fix it hahahah. but weight Vs weight this one is the same as my 10 inch coil. 1 pound 450G.

[geoscash1]

Personally, I'd go with a 3dss and use litz wire, either 175/44 or 240/44 at 7-1/2" form to fit an 8 in housing and staying between 300 and 325uh. After many tests and lots of wasted wire, this has turned out to be the best so far especially with any mods. My particular units will pick a us nickel at 10 inches easily and 5/6 in for 1 gram nuggets.