reversing the 2n2222

[bluebenz1]

I have just finishes fiddling with a newly built barra. I have changed to a tip127 and also swapped the metal 2n2222a coil for a plastic one.
With the plastic 2n2222a in the orientation on the board i could detect a leatherman penknife at about 500mm but could not detect a titanium ring (that i could previously detect). After much head scratching and twiddling of the 25k pots...I decided to invert the plastic 2n2222a set pi 6 on the ic to 0v as per usual...and now it WILL detect the titanium ring at about 8inches +- 200mm but the leatherman only gets detected at around 250mm.

So I have gained sensitivity but lost depth of large objets....Does this seem correct...?

[6666]

If you use ether a plastic or metal case 2222 the correct BCE connections are written on the PCB,

[bluebenz1]

Thanks, yes i see it now...

[Koala]

To your original question. Yes with the 2n2222 the wrong way round the detector behaves differently. I found that the detector still worked quite well if the volts were quite low otherwise the TIP got very hot. Also the detector discriminated iron quite well.

Yours sound like the delay was quite large explaining why large targets are deep but others are not detected

With the 2n2222 the correct way round detector requires much higher volts (obviously don't go past the max voltage of your regulator) and some readjusting to get some distance back but now you will find the TIP only get warm.

But I have lost the ability to discriminate iron


I have not experimented with different coils yet but suspect that with a bit of tuning that almost all lost performance can be regained.

[bluebenz1]

that all makes sense...thanks....the letter markings on the board are correct but the half moon graphic is incorrect....!!!....I have tried 12v and 10.8v on this board but there seems to be no difference in its ability to detect. I am hopefully going as a guest on a day out with a detecting club this coming wednesday.....very curious to see what it does...hopefully something !!!!