surf pi 1.2 problem

[geoscash1]

Thanks for the message porkluvr,

You were correct in that it (mine) was backwards so I fixed it by moving the wire to the right of center pin, so now it reads correctly, when in full clockwise it reads 22.07 (my mistake, it was 22k pot, not 10k), full counterclockwise reads 00.00. So technically I have the exact same issue (if its an issue at all) that kalaka has, it detects great (coins and gold/silver) in full clockwise position (100%) and backed off to about 80% dial. Beyond that (decreasing to counterclockwise) it doesnt detect anything especially gold. I'll get a faint and very slow to rise signal at about one inch with the delay in full counterclockwise position up to 80% dial with a pair of pliers but nothing else.


So I assume it acts somewhat like a descriminator in that as you decrease or shorten the delay it will eliminate objects/depth. I was under the assumption though that it should be opposite in that it should work well (good detection/depth) in the full counterclockwise (shortest delay) versus full clockwise (longest delay) .... So with that being said, it must have an issue somewhere If my thinking is correct...


Dam I'm so confused with this thing....lol....


Kalaka, I feel ya brother, its the little things that can drive ya to drink...

[porkluvr]

Kalaka, I apologize for getting snappy with you earlier, and also apologize that my original "solution" was totally wrong. Bad form, to say the least.

I have already said this, but let me say it again:

If using a panel mounted pot for P3, it becomes necessary to know that the pot is wired correctly before an analysis can be made on the issue of does your coil want improving (unless you have an oscilloscope to help you).

Here is how you could easily ascertain the correct wiring:

Turn the P3 dial counter-clockwise (CCW). Leave it there for the next few steps.
Place one meter lead on the center terminal.
Using the other meter lead, measure resistance from center terminal, to each of the other two terminals, in turn.

Make a note of which two terminals measure ~0 ohms between them. Solder two wires, one wire to each of those two terminals. Solder the other ends of those wires to the PCB. Take notice that one of the traces for P3 has holes for more than one wire and please make sure to not solder both wires together on that single trace! It makes absolutely no difference which wire goes where, just so long as you use the correct two P3 terminals and the correct holes on the PCB.

If you get that right, then it will be a whole lot easier to determine if a coil has good sensitivity or bad. Without that information, and without test equipment, you will have more questions than anybody can easily supply answers for.

If you choose to use the trim-pot that was supplied with the kit, you can simply ignore this.

Why would Silverdog supply a trim-pot instead of a panel pot.... hmm I don't have a clue. $$$$

edit: I won't beat this horse any more, I think it is dead.

[kalaka]

Both you guys, I made a big mistake telling how to connect P3.

Use the two terminals that give you minimum resistance (as measured with ohmmeter) with the dial rotated fully counter-clockwise, and maximum resistance with the dial rotated clock-wise. I think those are going to be the center and the one on the right (with the dial facing you and the terminals probably facing up.

Pfft. Sorry about any confusion. I had it exactly backwards.

For minimum delay the pot should read zero ohms, and should be fully CCW. I hope you have a multimeter and can do this for yourself. It is really very simple.

edit: let me say this again, turn the dial fully CCW. Measure from the center terminal of P3 to the other two terminals, one by one. The two terminals that measure near zero are what you should use.

I slept on the problem and then came back with the wrong answer, how about that!! (not good)

porkluvr i made the test with multimeter on P3.fully clockwise give 0.0ohm and fully counterclockwise give 33,8ohm.

[porkluvr]

porkluvr i made the test with multimeter on P3.fully clockwise give 0.0ohm and fully counterclockwise give 33,8ohm.

Let me go real s-l-o-w so that I won't make another dumb m-i-s-t-a-k-e.

When dial is set CCW I believe you should have minimum ohms (near zero), and when rotated fully CW you should have maximum ohms, so what you wrote seems to indicate that things are reversed.

Simple fix:
Leave one wire on the P3 center post and move the other wire to the opposite post from where it is. If it is on left, move it over to the right. If it is on the right, move it over to the left.

That should make P3 wiring correct and makes it easier to determine what (if anything) needs to be done with your coil.

[kalaka]

porkluvr i test it again and i upload photo.
i have trim pot (silverdog kit).in post 37 i have photo my pcb.
in 0ohm i detect gold very good,is this correct?

[porkluvr]

Good is good.

edit: What you need to do now is to take the machine outdoors and make sure that operation remains stable.

One other thing... I forgot to mention in one of my previous posts that using multi-stranded wire is superior to using single stranded wire. That is because a high frequency pulse encounters less power loss when using stranded wire (all other thing being equal).

Furthermore, tin plating rather than silver plating, is superior (mind you, this is my opinion and I hesitate to state this as fact) because, well, a proper Litz wire would be the best option and tinned stranded wire is about the next best thing. At pulse frequencies, silver plated multi-stranded wire ("stranded wire", for all you English speaking folk) acts like a single strand of wire more so than it acts like multiple strands.

Also, using larger gauge wire is not necessarily going to give improved performance because if you turn off the FET before the coil current has had enough time to stabilize, then the flyback pulse has to overcome forward inertia (for lack of better words) before it can start collapsing. Lower values of coil resistance mean that it might take longer for the coil current to reach its peak value.

Mind you, this is not my brainstorm here, these are ideas I have gleaned from reading some of Ferric Toes' posts and he is generally assumed to know what he is talking about.

[kalaka]

porkluvr thank you.
I will make new coil with stranded wire and I posting the test results.