surf pi 1.2 problem

[porkluvr]

It's simple to do.... but it's difficult to describe. I am working on writing instruction so that we can all know that we are all reading from the same page (so to speak).

Unfortunately you guys appear to be using two different PCB designs which doesn't help, but this is not rocket science. Before proceeding, must make sure everybody know which direction is up, down, and sideways...

Tomorrow is another day. G'night, all.

[porkluvr]

Geoscash1 your wiring is greatly simplified by only having two wires. Holding the pot facing you with the terminals facing upward, you should have the wires going to the center and left terminals. Doesn't matter which wire is which, so long as you use the correct terminals on the pot. As you rotate the dial from CCW to CW, resistance between those terminals should go from ~100kΩ to ~0Ω.

I am still working on kalaka's problem. Silverdog apparently did not realize that he could have reduced the number of wires going to P3 and he probably left correct wiring up to his customers ability. So, assuming the center wire would go to the right place, any non-electronics type person would have about 50% probability of getting the other two wires to be good.

edit 1: removed "greatly" from before the word "simplified".
edit 2: put it back

[porkluvr]

I don't have Surf PI but I assume that it is normally for P3 would be wired so that CCW (counter-clockwise) is shortest delay and CW is longest. If you must turn P3 CW to detect gold, I think maybe P3 is wired backwards because gold should be detected with the shortest delay selected. (?)

Ouch, whoever wrote that needs to learn to proof-read his work more better! What an idiot! ar ar

[porkluvr]

Big problem figuring out how Silverdog's PCB can work at all:

On the Surf PI schematic, U4 pin-9 is connected to C11 and R28. On the Surf PI 1.2 PCB wiring diagram that I have, pin-9 goes NOWHERE.

That is a severe discrepancy. I can be of little assistance until this is resolved.

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For some odd reason I am unable to upload a 50kb jpg image. I have never had this problem before.

Admin, what is going on?

[6666]

On my bare board U4 pin 9 is connected to large trace on TOP of pcb, which on the latest schematic is U+

[porkluvr]

On my bare board U4 pin 9 is connected to large trace on TOP of pcb, which on the latest schematic is U+

Absolutely. Thank you.

I already had figured out that that's what had to happen, pin-swap for pins 8 and 9. Process of elimination. (I could not see the V+ trace on a photo of a populated board but it had to be there.)

I have this figured out but it will have to wait until morning so I don't write hastily and say something really dumb.

[kalaka]

friends thank for your help!
i buy today wire 0.80.i make new coil.I believe to make a good coil now.
photo for wire and my pcb.

[porkluvr]

That's wrong kind of wire in my opinion.

I have a long letter all written up describing the wire you should use, but I have it saved for after we make sure that your potentiometer is wired correctly. When you are in over your head, it is good to solve ONE problem at a time...

Stranded wire is best, and there is more to be said, but like I said, one. thing. at. a. time. Also, I think you're better off with the same gauge wire you had used previously, 0.45mm is best because with it, you could easily construct a coil with the correct inductance an also correct resistance. Build a coil with 0.8mm wire and your resistance will be too low. That does make a difference in how your system reacts.

I still need to find out why I was unable to make a photo image attachment to my previous post. I am still unable to load images this morning.

[porkluvr]

About our P3, I would like to post a photo but I am unable to. Therefore I will have to describe in words what to do.

Hold the potentiometer so that it is facing you and with the terminals upward. (You should not be looking at the backside of the pot, you look at the front). REMOVE the wire on the right-most terminal, you don't need it... you should use only the center and left terminals on the potentiometer

On the back of the board, locate the P3 trace that is connected to U4 pin-8 (U4-8 ) and C9. One wire goes to that trace. Only one. Use either open hole you choose. Use either wire, it makes no difference

The other wire goes to the P3 PCB trace that is connecting to resistor R25. Unfortunately, Silverdog has apparently rewired the PCB slightly diffrently from what my schematic suggests but that is not going to cause a malfunction in and of itself, it just makes things a little more confusing.

As you rotate the potentiometer dial from CCW to CW, resistance between the two used terminals should go from ~100kΩ to ~0Ω.

If you have understood me and complied with my directions, P3 will now be wired so that CCW is minimum delay and CW is maximum delay.

Now you can worry about the coil....


edit: Kalaka, I see you have removed the panel pot and installed a trim-pot in its place.
You just wasted my time. I have yard work to do.

[kalaka]

i install again a trim-pot why this pot was in the silverdog kit packet.

[geoscash1]

Thanks porkluver for the great explanation.... kalaka, hope you can get yours working well soon.

Mine was obviously a simple one to understand and figure out or change, I just don't have any use of the
pot beyond 20% of the way, the rest of the way (clockwise) does nothing, I'm thinking it may be because I am
using a 10k pot (based on parts list and pcb image) so maybe I'll swap it for a 100k pot and see what that does.

p.s.
I had 3 different threads open last night when I replied and ended up posting in kalakas thread instead of the sm pro
one I was reading, dont ask me, just to many things goin on at once and ended up in the wrong place with basically
the same issue but opposite of kalakas so it fit here I guess.

[porkluvr]

i install again a trim-pot why this pot was in the silverdog kit packet.

Ok, then talking to you is like talking to a brick wall.

[kalaka]

porkluvr why do you say that for me?both pot work exactly the same.clockwise detect gold very good (20-25cm medium gold ring),counterclockwise dont detect gold.

[porkluvr]

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]

porkluvr why do you say that for me?both pot work exactly the same.clockwise detect gold very good (20-25cm medium gold ring),counterclockwise dont detect gold.

I was trying to eliminate the possibility that your P3 was wired backwards. Having P3 wired in reverse would make it difficult to analyze some other problem that you may have.