SURF PI HELP

[geoscash1]

Thanks daverave, I've double checked all solder joints and I'll double check for mistakes to be sure and then swap out the IC's mentioned...Appreciate the reply..

[daverave]

daverave, were you able to sort out the pulsing in the audio? mine has that same issue, no steady threshold, just very erattic and very hard to distinguish signals beyond 6 inches at all with all the noise..

check for any solder shorts or mistakes....failing that replace the 4093 & 4066 ic's....that should cure the problem.

[geoscash1]

daverave, were you able to sort out the pulsing in the audio? mine has that same issue, no steady threshold, just very erattic and very hard to distinguish signals beyond 6 inches at all with all the noise..

[daverave]

my detector has a problem which i have to sort out...i was doing some wiring last night and now the audio is pulsing instead of steady...when i turn the delay control seems to get worst...hope i can fix it.

[kt315]

the inductance of the coil will be not something fantastic... it is ordinary classic for PI in 300-350uH range.

while main issue for us is to get an inductance of inner winding and an inductance of outer winding, being splitted one from another. second issue is damping resistor's value on inner winding. then we get all data we can right count the coil.

[daverave]

i had a friend visit me today and he bought with him his whites dual field pi...i was hoping to measure the inductance but pcb had plastic box around it which i could not open so i gave up....but i did take current measurement and was supprised to see that it only draws about 44 ma from the batteries....i compared the depth with my home made surf pi and there was very little difference...both detected old uk penny at 12" but on a thin section 9ct gold ring the dual field did about 8" which was about 1" more than my machine...but on a small thick 18ct gold ring only about 8-9" which i felt was dissapointing from the dual field...but noticed even small silver ring gave good depth compared to gold item of the same size.

[daverave]

i will have to use the 5 ohm coil as its already made but will make sure from what you have told me that the next coil i make will be low resistance...cheers for your help with my problem.
thanks Tepco.

[Tepco]

Use larger diameter wire for coil, resistance of 5R is too high, limiting peak pulse current, keep it below 2R, do not add any resistance in series. Normal consumption is around 50-60mA.

[daverave]

i was expecting around 14 - 16" on old uk penny...i get about 6" on a thin section gold ring (small) cause my coil is 5 ohm and the current is 37ma i feel maybe i should increase tx pulse to around 100ma...surely a pi detector should draw more than 37ma....what you think ????

[Qiaozhi]

i did some tests today on my surf pi and its drawing from the batteries only 37 ma with no signal present...seems a bit low to me...i think thats why im not getting the depth on some items...i can hear an english old penny at around 12"...what you think anyone ??

I would say that's a good result.
What depth were you expecting?

[WM6]

12" on penny is great result, low battery drain too.
Even more, such good result you can expect in soil too (not the same thing with VLF air tests).
Congratulations.

[daverave]

i did some tests today on my surf pi and its drawing from the batteries only 37 ma with no signal present...seems a bit low to me...i think thats why im not getting the depth on some items...i can hear an english old penny at around 12"...what you think anyone ??

[daverave]

thanks mate for that original spec...did the original surf pi work better than the modified version ???

[kt315]

...

Change out #Q2= TIP32C with a IRF9640
Replace the 220 ohm resistor with a 390 ohm resistor (1/4 watt)

When finished installing the components cut a piece of aluminum foil 3/4" square.
We will use this to adjust trimmer pot #R25 turning on the unit and adjusting
the threshold so you can just hear it, adjust R25 for best response when the
3/4" foil is passed by the coil. This should do it.

You can try removing diode #D3=1N4148 and installing a jumper in it's place.
This will allow a little finer adjustment of the threshold on the soft deep ones.

[porkluvr]

This has been doctored, but I think it is a pretty fair representation of the original drawing.