PI-1 build

[raygdunn]

Hi Ray
because the PI-1 has no EF cancel , do you get a beep at the end of each sweep ?

Hi 6666

I was unfamiliar with the swing effect, when I recently built the Barracuda.

My best guess is a lower level of sensitivity. I spent three hours with both yesterday and was somewhat surprised at what the PI-1 failed to detect.

Ray

[raygdunn]

hello ray

if you want to build a pinpointer use pi-4 Project
right size

i dig out the pi-1 and will see what i can do
cant imagnine that i am to stupid to get this working

can you say what depth you reach with pi-1
so i can imagine the performance

Hi Bernte,

Gosh I lose track. It would appear that I breadboarded the PI-5. Pulled out the back end and converted it to a PI-4, which is what's still on the breadboard. So it would be the Pl-4 I had sensitivity trouble with and yes it seems suitable for the pointer. Once I've figured out the coil and robust case for same.

The Pl-1 coin range is debatable. With a 10" coil (149uF, ~0.7ohms, 300pF, which sounds all wrong. I made it before I could test inductance, etc.) For a UK Victorian penny, air range really is only about 8cm for a good beep. But extreme limit on a headset for a hint of something is around 30cm. The practical in field detection level be somewhere in between and with the coil I have, much would be buried by ground noise. Maybe I should go back to a regular coil. I first used a regular 16cm coil and assumed the current larger coil had more depth.

With a year more knowledge, perhaps I should be looking at this again...

Ray

[geoscash1]

Hi Ray
because the PI-1 has no EF cancel , do you get a beep at the end of each sweep ?

Ok now that I have a bit more info, I need to know since I am not familiar with the term or finding what EF means? I assumed it was electro magnetic interference or ground interference but am seeing that called different terminology. I know that may be a dumb question but I really don't know.

[6666]

Ok now that I have a bit more info, I need to know since I am not familiar with the term or finding what EF means? I assumed it was electro magnetic interference or ground interference but am seeing that called different terminology. I know that may be a dumb question but I really don't know.

EF is the earth field, basicly the earth has magnetic lines of force around it, when you wave a coil back and forth through the lines of force you will induce a small voltage/current into the coil and that will be interpreted by your MD as a target unless you have a second sample to cancel the EF from the target, thats why the surf / bara etc has 2 samples, you can simulate the effect by waving a non metallic magnet in front of the coil IE: fridge magnet.
You dont need the second sample if you can put up with the beep at the end of each sweep.

[geoscash1]

Thanks 6666, much appreciate the explanation. I had assumed it had something to do with the ground or some magnetic/electrical interference
but wasn't to sure on the subject so thanks for setting me straight on it...

[geoscash1]

Diode D3

Question, on the PI 1 schematic, there is a marking for a diode next to the Q3 2N3819, is this a typo or is the diode missing from the schematic, I noticed there is another place on the schematic where a diode is marked D3 next to R5...

[Qiaozhi]

Question, on the PI 1 schematic, there is a marking for a diode next to the Q3 2N3819, is this a typo or is the diode missing from the schematic, I noticed there is another place on the schematic where a diode is marked D3 next to R5...

[ATTACH]35991[/ATTACH]

If you're referring to the arrow at the gate of the 2N3819 ..... that is part of the FET symbol. It's not a diode.
I'm not sure what you're asking about D3.

[geoscash1]

If you're referring to the arrow at the gate of the 2N3819 ..... that is part of the FET symbol. It's not a diode.
I'm not sure what you're asking about D3.

If you look at the cropped pic I added in the previous post, it shows a "D3" just to the left of the trace (gate line) to the Q3 2N3819, is the D3 just referencing the gate arrow or is there supposed to be a diode on that trace going to the gate? Reason I ask is there is already a D3 diode on the schematic next to R5 just above to the right of the mosfet.

New pic -

[rickb]

The "D3" next to the fet on the PI-1 is also present in the 2nd edition, but is removed from the schematics of the PI 2 and 3. Looks like another entry for the errata.

Rick

[Qiaozhi]

If you look at the cropped pic I added in the previous post, it shows a "D3" just to the left of the trace (gate line) to the Q3 2N3819, is the D3 just referencing the gate arrow or is there supposed to be a diode on that trace going to the gate? Reason I ask is there is already a D3 diode on the schematic next to R5 just above to the right of the mosfet.

New pic -
[ATTACH]35992[/ATTACH]

OK - thanks - I see what you mean now.

The "D3" next to the fet on the PI-1 is also present in the 2nd edition, but is removed from the schematics of the PI 2 and 3. Looks like another entry for the errata.

Rick

Yes, it's some random text that appears to be in both editions.
That's the first time anyone has noticed it.

[geoscash1]

OK - thanks - I see what you mean now.


Yes, it's some random text that appears to be in both editions.
That's the first time anyone has noticed it.

Ah, good. was going to add a diode to that trace until I saw there was a D3 elsewhere, so glad to be of assistance....


p.s. I'm doing a bit of modifying to this, hopefully it will work out.

[Carl-NC]

That's the first time anyone has noticed it.

First time I've noticed it, too.