Project PI opt2

[seras]

anibody known if I can use a coil square of 70cmx70cm in pi1/opt2 project and what value I use for R11 and R12? and other modification?

Thanks best regards

[Reg]

Re: Project PI opt2

Hi Seras,

I haven't built a coil that large, but I just built one about 46 cm in diameter for my Goldquest clone and it worked fine, so I see no reason you couldn't build one for the PI project.

If the coil is built keeping the inductance the same as your standard coil, then you shouldn't have to change the value of any resistors.

You will probably have to use a longer delay to make the coil work, but this is because of the increased capacitance of the larger coil.

Just remember to try to keep the inductance the same for all of all coils you make for the detector and it should work.

You could use a larger inductance but this would also require a greater delay to make the coil work.

If you make a coil with less inductance, then most likely, the coil will oscillate and the damping resistor (R 11) will have to be reduced in value.

Reg

[Reg]

Re: I forgot to mention

Hi Seras,

I forgot to mention something that might be of value. If you build a larger coil and it does oscillate, you can add a resistor in the coil housing across the coil to dampen the oscillation, rather than change R 11 and/or R 12. Another way is to add an extra resistor across the coil in the coil cable plug.

Either method allows you to keep things the same on the pc board.

It is what I do and it works fine. I have altered the inductance on some of my coils and that did require I change the damping resistor.

In the case of the larger coil I mentioned in the previous post, I did lower the inductance a little which required the damping resistor be changed. I just added a resistor in the plug on this coil.

Hope this helps.

Reg

[Claude]

PI -1 opt2 is a Goldquest clone?

Hi Reg,
Sorry to interfere, but I see you talk about it as a Goldquest clone, is it true?
Claude

[Reg]

Re: PI -1 opt2 is a Goldquest clone?

I Claude,

My PI that I presently use is a modified Beachscan which I got from Eric Foster. So, it is not a PI-1, but the design is somewhat similar to the PI-1.

One of the big differences is the coil current and FET used. The PI-1 series will draw much more coil current which will make it harder to get the minimum delay as short as I have my GQ clone.

When I bought the Beachscan, I didn't know if it could be used for nugget hunting so it was a gamble. Through some mods, I was able to develop a very decent nugget hunting PI.

I refer to my PI as a GQ clone because it is much more like a GQ than the old Beachscan.

Reg