Surf PI Pro

[sdesic]

I am thinking of 12 V battery for power tool or 10x 1.2V AA battery pack or something like battery from UPS 12 V 7 Ah (too much weight)
This pinpointer is possible on Surf PI PRO ?
You can experiment with it and then you can write about it here

Instruction Manual from Whiteselectronics
http://tinyurl.com/c98w8g8

[au1]

sdesic,
I used a 9volt battery because thats all I had available at the time.
I bought 8 AA 1.5V cells today. After powering it up, I see very little difference, if any, than using a 9 volt battery that was only producing 8.5 volts. Its good to know that this device will work efficiently down to that voltage. Out of curiosity I applied 4.5 volts just to see if it would still function. It does, but at about half the detection range.
I'm consistently detecting a coin at about 10 inches on the bench. Which is far better than any I've built so far. My friends White's 5000 won't do any better.
The fact that this unit will accept a varity of coil arrangements is a plus too. The coil's I've tested don't appear to need any shielding either.
So far with the coil configurations I've tried, none seem to be very sensitive to gold. I'm testing with an approximately 2 penny weight nugget. Detects at about 3 inches. Which really isn't bad, considering. Most likely need to test with smaller coils.
I'm curious to hear about your results, once you get your parts.

[sdesic]

That is about it... not bad for home made metal detector.
Can you specify what coin are your using at 10 inches, and if you can test with smaller and bigger coins.
Silver coin if you have one will also be interesting.
You should also try detecting a gold ring and than post results.

I have asembled averything except IC's and potentiometers.
Still to make coil and housing...

[andva]

Hi all!

I have finished building my Surf PI detector, the PCB was Surf XX which can be found in this forum. I tried using it on field, the results were good. Sensitivity to coins in air testing was about 20-27cm depending on coin size and material. When the detector was turned on in the house, with minimal treshold there was a little noise on the speaker because of electric devices. In outdoors, this noise was no more audible. The coil didn't detected the ground even without shielding, so I thought I've built a very good detector.

Then an accident happened.....

I used a poor quality wire that connected the PCB to the coax head cable connector, and somehow this crap wire broke and made the coil short - during operation.....
I removed this wire and built in a new one. When i turned the detector on the next time I realized that the sensitivity fell down about 1/2 of the original, so now the machine detects coins at about 10cm. The other bad thing what I found there is no more noise when I turn it on indoors. So the detector is still working, but it became very-very-very insensitive...
Which part could be damaged? I tried changing the IRF9640 FET, the 2200uF capacitor, 5534, 4066, 4093 and lm358 IC-s but it had no effect.
Does anyone have an idea how to repair? Should I change all the semicondutors including IC-s, diodes and transistors? I guess the resistors should not be broken.

Thank you for your attention and help, and sorry for my bad English!

[au1]

sdesic,
I'm getting 10 inches on american nickle,penny and quarter. I sold all my gold and silver last year when the price got up to about 1,800.00. But I do have a silver half dollar that I just tried. It detects at about 8 inches. And like I said before, I tried a small 2 penny weight gold nugget. The gold nugget detetcted at about 3 inches. I'm experimenting with a smaller coil.
Most places I search 4 inches is deep enough. When you get yours working you'll see what I mean about pinpointing. With the coil laying on the floor I can place an object in the middle of the coil. It will sing for a couple seconds and then stop.
You said you where in the process of making a coil housing. Can you go into detail what you're using? I'm in the process of acquiring a vacuum forming machine.

andva,
I don't know enough about electronics to be of much help. Wish I did. Due to my sloppy desoldering, I'd probably just etch another board and start over. Did you buy a kit or etch your own board? You might get some help here. Or..... you might not. I would suggest checking some other electronics forums. I've found a couple that are very helpful. Post a schematic and see what happens. I'm going to see a friend who is pretty good at electronics and I'll show him a schematic. Maybe he has an idea.

I'd check all the resistors first anyway.

[sdesic]

andva,

you should check your power source if it is 12 V and voltage on PCB 5 V around 78L05.
What is your power source ?
Also R6 390 Ohm 2 W ... look for burn marks.
You can probably send PM to one of guru's on this forum.

au1,
I woul'd be happy with that kind of depth.
Pinpointing can be done by detecting from multiple angles... you find your coin and change your direction of swinging
and make like a cross to pinpoint ... or you can build another smaller device (coil and surf PI)
or you can make another coil and switch between them if needed.
I don't know what happens when you switch coils while power is on.

Housing that I mentioned is for PI and battery, or two boxes.
Coil will be placed between two foam boards or two lids - nothing fancy.
I had one idea with some kind of plastic square but it is 16x16cm, will see about that when device is finished.

[au1]

Yes, I'm very happy with the sensitivity. I've found that by having the ability to adjust the delay on the fly helps detect gold versus copper clad coins. I might try a coil out of speaker wire as shown on the blog. But I think 8 to 10 inches seems to be the max. I showed the schematic and the pinpointing mod I posted from another thread on this forum to a friend this evening. After he looked at it he said there was no way that could possibly work. By following that diagram when the circuit was open there would be no sensitivity at all. One has to watch what people post. Guru simply means number of posts.

andva,
I had something very similar to your problem happen to me. I had a loose solder joint connecting the coil to the coax. It displayed exactly like what you described. You might check those connections.

[andva]

Thank you for your replies.
I use 10x1,2V 2100mAh cells and I measure 12,67V when detector is turned on. The power consumption is about 59mA with minimal volume or no sound, 114mA on maximal volume (this high only when beeping loudly).
The pulsewidth on the coil is about 34-35us. The damping resistor doesn't seem to be fried and the measured resistance is correct (i use a suitable potentiometer because I'm still experimenting with coils).
At 78l05 the voltage is +4,93V, at the output of 7660 is -4,2V. These values were the same when the detector worked well. I checked all the IC-s if they receive the +5V and -5V and they all get the values written above. So the voltages are correct in every places but it is insensitive even with new IC-s. The next thing will be replacing the transistors and diodes. I suspect the 2n3906 transistor might have got too high current.
The PCB is my own etched one. I don't think it's necessary to etch a new PCB but probably I will replace almost all the components....

[sdesic]

Andva,
you shoul'd check for bad soldering poins too
maybe it was mechanic stress
try bending PCB or taping solder points

[andva]

Hi!
I solved my Surf problems. There were some other crap wires that connected potentiometers with PCB. These had been replaced and detector now working well. Thank you all for your help and thank ApBerg for his great Surf XX design.
I wish everyone a merry christmas and very successful treasure hunting!

[sdesic]

Andva,
great work enjoy your Surf PI Pro.

Au1
Is this pinpointer good for you ?
http://www.easytreasure.co.uk/probe.htm
it is commercial but you can see what you need and find similar device.

[joop]

Just finished the build of my Surf PI. Sensitivity is incredible! Still have to do a bit of finetuning... I have used ApBerg's PCB design.

I could not get any pulses from Q1 when I first tested it. Somehow R17 and D4, which supply a clock signal to the ICL7660 forced Q1 into saturation. I have removed both components and connected 220 pF from ICL7660 pin 7 to ground. Found this solution in the data sheet. Anyone having problems feeding the clock signal from the 555 into the ICL7660?

[sdesic]

I have finaly made my Surf PI pro from J. Owen design and ApBerg's PCB.
Don't have any sound on speaker.
All pots are in middle position.

I had problems finding MPSA13 - got replacement BC879.
R34 is 22R from PCB design not 150R

Measured all voltages
Connected 12V from power adapter
7805 has 12V and 5 V
12V on pin4 and pin8 IC 555
12V on emitter of 2N3906
12V on S IRF9640
+5V on IC 7660 pin8
+1 V on IC 7660 pin5 (?)
+5V on IC 4093 pin 9
+5V on IC 4093 pin 1
+5V on IC 4093 pin 12
+5V on IC 4093 pin 5
+5V on IC ne5534 pin 7
-4.45V on IC ne5534 pin 4
R18 is connected to threshold pot 10k and on other end is -4V
Speaker is on + 12V and on pot 1k
on IC 4093 pin 14 +5V
on IC 4093 pin 7 -4.45V
on IC 358 pin 8 +5V
on IC 358 pin 8 -4.45V
on IC 4066 pin 14 +5V
on IC 4066 pin 7 -3.5V to 3.94V depending on POTS

[ApBerg]

You need around - 4.5 volt at the ICL7660A pin 5 ... so not good, see you use a icl7660 smd.. check if this can work with 12 volts some go only till 10.5 v !

Check also the pins from the bc879 and mps13, not the same I think.

Check also the current the circuit take's , without audio out around 50 mA

Succes

Ap

.....now I see you got -4.5 V on the needed points in the circuit ... so look again at 7660/5 must be ok !??

[sdesic]

ApBerg thak you for your fast reply.

Here is more data.
I have -4.31 V on pin 5 IC 7660
that 1V is on pin6 sorry
I used smd IC because I can't find normal one in Bosnia must check for that voltages ...

Pinout for darlinton's MPSA13 and my BC879 are diferent - both NPN
I think I got it ...
faced right MPSA13 has
C
B
E

BC879 faced right
E
C
B
i turned base to Base on PCB, middle one to top C and first from top to E


Current for device is about 60-70mA.