Surf PI Pro

[sdesic]

New start

[sdesic]

My MD doesn't detect nothing so there is something else... It would detect on 1 inch with good board or oscilating TLC555
358N or 358P is issue of depth.

[sdesic]

This looks like professional job, on boards and all together.

[au1]

My home-made Surf PI Pro.

[au1]

I tried a NE555 and it wouldn't work for me. And with a LM358P I had no sensitivity. Maybe don't scrap your old board just yet. I liked this detector so well I bought lots of parts and built a few boards. IM me if you have a problem sourcing parts.

[sdesic]

My parts order was originaly as on project, but my order was changed and I received these.
They say that it is OK for most projects ... maybe not this one.
I have etched new PCB and ready to start fresh.
Tonight I will drill al holes, tommorow I can look for parts.
China has New Year holiday's until 25th.

[au1]

IC's are CHN NE555N and LM358P

I hate to be the bearer of bad news, but thats your problem. You need a TLC555 instead of NE555. If you look at the data-sheet there is a big difference. If I recall correctly the TLC555 runs at 2.1 MHZ.
And the LM358P only has about half the gain as the LM358N. I have 50 LM358P here and trust me, they won't work. It took me about a week to figure this out.

[sdesic]

I made coil with 10 more turns and same thing, I know
I have none control in those pots. Volume works and trimmer 5k works for something.
IC's are CHN NE555N and LM358P

[au1]

From my experience I've found the coil to be very forgiving. And even with too many or too less windings it has still worked. Even inside with alot of interference. With the specs you posted I'd find it hard to imagine thats your problem.

And as a side note. If you hook the sensitivity pot up the way it shows then you would have to turn it counter-clockwise to increase.

Could you post the exact part numbers/letters for the 555 and 358.


Mine doesn't make any noise without the coil hooked up either. Simply twisting the coil wire to the coax didn't work for me. I had to solder it even for testing.

[sdesic]

With coil far away ... same thing
will try to make another coil ... more turns ... more ohms

[sdesic]

Chance PI with same problems

http://www.geotech1.com/forums/showthread.php?18079-Chance-Pi-problem-%BF%BF%BF&highlight=constant+sound

[sdesic]

PI Pro is not making sounds without coil... must be problem with metal close by or coil itself.
I'll try distancing coil from everything... meter or two.

Here is one similar problem on forum

http://www.geotech1.com/forums/showthread.php?18079-Chance-Pi-problem-%BF%BF%BF&highlight=constant+sound

[sdesic]

That is still not the way I interpret those two sheets. But, don't let me stop you - feel free to use either/or. Maybe I'm dyslexic and never knew it.


The greater point is, before installing a transistor in a new project it is wise to electrically check the various transistor pin-outs against the PCB layout.

(Like that's ever going to happen )

I was making mistakes with pinouts of transistors and lost few days and maybe more.

[sdesic]

Hey Sdesic,
Sorry to hear about your detector not working. Thats's a bummer! I can tell from your board you put forth a fair amount of effort. If the only difference between mine and yours is the MPSA13 then I'd lean towards that being the issue. You can't source them? Can you receive packages from china? If so, you can find most parts reasonable and free shipping. It might take 2 months or more to get them though.
Here's a couple things I found out about this layout. Due to the size, I replaced the electrolytic feeding the sound with a 220uf even though the 470uf worked ok. I also
used a 1/2 watt resistor for the 12 ohm. Everything works good.
About replacing R2 with a trimmer. I doubt thats going to help your problem. But it will definately help the sensitivity. It apparently applies more current to the coil, the lower the resistance. I'm running mine at about 2K. Got about 3 to 4 inches more reach. But at the cost of shorter battery life. I don't mind. Batteries aren't too expensive.
And by reducing R2 I also noted that I get some unusual noise that wasn't there before. I just turn the threshold up a bit. All is well.
I'd offer to send you a MPSA13 and a ICL7660 but I fear what the postage might be to Bosnia.

PS. I used 150 ohms for R34. But I doubt thats your problem.

Good Luck!

I can order from China bur as you say it would be month or more untill it arrives.
I am going to etch new PCB board this is gone... I think there is post about similar problem on forum, so I will search for it.
Friend of mine has inductance meter - I hope - so we can measure coil inductance.
Must try step by step ajustments for PI.
My coil is not connected by coax, I used two ordinary 20cm wires for testing.

[porkluvr]

I think you are wrong about that pinout
Siemens and Philips have same pinouts ... TO-92 housing
http://www.datasheetcatalog.net/de/d.../7/BC879.shtml

That is still not the way I interpret those two sheets. But, don't let me stop you - feel free to use either/or. Maybe I'm dyslexic and never knew it.


The greater point is, before installing a transistor in a new project it is wise to electrically check the various transistor pin-outs against the PCB layout.

(Like that's ever going to happen )