I need Help with Surf PI 1.2

[yako84]

Hope you experts can help me. I have built the Surf PI circuit and 4 diferents coils.
Don´t detect metal, doesn´t do anything, but if I touch with hands, do a constant noise, no matter if I put coil or not. Please help.

[Luuk]

I would suggest you start with this thread.
http://www.geotech1.com/forums/showt...i-kit-no-sound

[6666]

Do the power supply voltages measure OK?

[yako84]

Yes, the voltage it´s ok

[Tepco]

Hope you experts can help me. I have built the Surf PI circuit and 4 diferents coils.
Don´t detect metal, doesn´t do anything, but if I touch with hands, do a constant noise, no matter if I put coil or not. Please help.

What type of “noise” you have, normal audio or something else, and what you touched?
Measure current consumption with and without coil, check if you can adjust offset at pin 6, 5534 (assuming + and -5V is OK.)

[yako84]

I don´t have any noise, but if a touch the board with hand, de beep is very high. I adjust the offset pin 6 , 5534 in 0volt with and without coil.
I tried with diferent coils, but doesn´t detect nothing.

[Tepco]

Measure current consumption from battery, how many mA, with and without coil, to see if TX drive to coil is OK.

[yako84]

How I measure that? thank you

[Tepco]

Disconnect batery + from pcb, set multimeter to 200mA range, connect between battery + terminal and surf board + connection and measure.

[yako84]

-01,8 with coil and -01,3 without coil.
Can it be?

[Tepco]

Check again, multimeter range and correct terminals on multimeter used, on many, current ranges are measured with common, and dedicated terminal for mA ranges, different from one used for volts or ohms. Expect around 60mA with coil, slightly less, around 1\3 of that without, detector must still make sound, to be sure you connected multimeter properly. If current is about same with and without coil, TX pulse is missing, if this is about normal, then something else...

[yako84]

the multimeter range is correct, in 200mA range. And I connect between battery + terminal and surf board +. The measure is:
1.8 with coil
1.4 without coil
How is wrong? Thank you

[Tepco]

Somehow, it is dead wrong. Current must flow from battery, thru multimeter, on correct range and connected to proper terminals, to surf board to power it, board must still produce sound when touched. Check connection again, if everything is correct, maybe blown fuse for mA range inside multimeter, switch to 10A range and recheck.


Anyway, assuming this is correct, next check voltage on U3B, pin 7, (integrator output) check if it changes in presence of larger metal near the coil, also vary delay pot and observe if it affect measurement. Check pin 5 and 6 too.

[Qiaozhi]

If you put on some headphones and place your head near the search coil (with the circuit turned on, of course) do you hear a weak audio tone? Note - the headphone should be completely disconnected from the circuit. If the TX circuit is running, the coil will inductively couple to the headphones, and you will be able to literally hear it working.

[yako84]

Sorry, before I put the multimeter in switch 20A range in 200m position (because in 200mv doesn´t do anything, I think that is blown fuse) and the measure is this:
1.8 with coil
1.4 without coil
And when I touch with multimeter do a litle beep.

I check voltage on U3, pin 7 and Measure is: 0.00 doens´t change is y put larger metal near the coil
Pin 5: 0.01
Pin 6: 0.01
Pin 8: 4,92

Ey, if a put some headphones and place my head near the coil y hear some weak tone!
(sorry becouse and don´t speak english well, I try)
thank you