My Surf PI works - thanks Silverdog and ApBerg

[Comp]

What values ?
thanks

I'm still bothered by low sensitivity on mine, too,... I get the same 80mm or so on a gold wedding ring..... I am 'tweaking' the supply lines to get em nice and clean,..... I have put a small red led in the ground lead of the 75l05, this is fed from the 12V line by a 4.7K resistor,... serves two functions, it gives me an on/off indicator, it also 'upps' the 5V line to 6.5V, or so, & the same with the neg 5V line, to minus 6.5V. I am filtering the plus and minus supplies to each chip with 47 Ohm resistors, and 4.7microfarad tant caps, and 0.1mic bypass ones as well, supplies are nice and smooth and clean,....and plus and minus 6V or so at the chips,... I used these values cos I have plenty to hand!!!!!!!

I havent got it quite all back together, yet, I am rebuilding it on 'blob board',.. just in case I have 'leakage' problems on the original board......

I will keep you posted/updated,......


Cheers, Fred

[TH Jim]

Hi Sean,

Those results are very impressive - could you post a picture of the ring you used or tell us it's weight and dimensions please? Similarly details of any other targets you use when you perform your comparison test would be good know.

Look forward to seeing your results, thankyou for sharing with us. Happy new year!

Cheers, jim.

[silverdog]

Have you seen this ? an error has been found which when corrected should improve your detection range


"Remember to swap your R18 and R22 around - as typo on the silk screen.

Use details to improve depth as in the link

http://www.geotech1.com/forums/showthread.php?t=18445

PCB and Schematic were ok - just typo on the silk screen.. "

[Sean_Goddard]

Sadly, somthing came up and I was unable ot take pictures of the waveforms (actually I'm STILL working on MY SM) but my friend has had to go back to base for posting.

We too some measurements of the Whites Dual Field coil and here is what we found;

R = 2.4 Ohms
I = 253 uH (1KHz)

That's the best I could do for the moment. Sorry.

[woodbob123]

Thanks to all

finished my first surfPI thanks to all who have worked on design, nothing nicer than when when you put a project together and it works first time all the credit goes to you guys. Put together a nice coil and finish this one, hopefully the IGSL will go together as nice

THANKS TO ALL

[golfnut]

With the Surf Pi the de Q ing Resistor slugs the ringing following a Tx spike,

it also is wired across the Rx input - slugging the return from the coil!


With separate Tx and Rx coils - the Rx coil will not have the loss introduced from the D Q resistor.


How much better would this be .

What results are people getting on these Surfs?

Steve

[Sean_Goddard]

Anyone thought if using an IGBT for this application?

[maxfly]

Hi all,

I have just completed my Surf PI board and have been testing it.
I also have low sensitivity, probably due to the fact that I can't get any response when adjusting the delay pot (makes no difference across whole range of adjustment). Pot tests okay, are there some simple test I can do with a multimeter to eliminate causes?

[6666]

Maxfly "Remember to check your R18 and R22 are in the right position - as typo on the silk screen." gives low sens if wrong

Use details to improve depth as in the link

http://www.geotech1.com/forums/showthread.php?t=18445

[maxfly]

Thanks 6666,

I have checked that out already, but will double check again.
My tune pot works fine, just no response from delay pot!!

[Brian Deese]

I also think that building the board and leaving the trimmers off until LAST allows you to soak the board in CLEAN isopropyl alcohol for half an hour or so to remove ALL contaminants, then coating the board with conformal sealer goes a LONG way to making the Surfmaster a LOT more sensitive.
Quote from Sean Goddard:

Is that only if the board is socketed? You cant put an IC under alcohol can you? I need to clean mine,it has low sens also,and the solder side looks dirty where I have handled it.I can only get about 4" on a us quarter.That has to be corrected.

[ApBerg]

I also think that building the board and leaving the trimmers off until LAST allows you to soak the board in CLEAN isopropyl alcohol for half an hour or so to remove ALL contaminants, then coating the board with conformal sealer goes a LONG way to making the Surfmaster a LOT more sensitive.
Quote from Sean Goddard:

Is that only if the board is socketed? You cant put an IC under alcohol can you? I need to clean mine,it has low sens also,and the solder side looks dirty where I have handled it.I can only get about 4" on a us quarter.That has to be corrected.

Hello Brain and other friends,

What I do is as follows...

Take a old toothbrush dip it in a bottle with Isoproponol alcohol, so that there is lots alcohol on the brush. Brush this over the copper side from the pcb.
If this is done take a sheet kitchen cleaning paper and put this over the sill wet pcb.
Now brush over the kitchen paper so that it picks up the dirty alcohol that is on the pcb. If not clean the first time than repeat this again. Watch for clean teeth between the ic's
I always do a last time cleaning without the paper.. so I can see it is really clean.

Regards.

Ap

[Davor]

Some 20 years ago we used canned freon to do that, and it worked miracles. Just spray it liberally and watch it bubbling dirt away. Too bad it is ruining atmosphere.

[Brian Deese]

Hello Brain and other friends,

What I do is as follows...

Take a old toothbrush dip it in a bottle with Isoproponol alcohol, so that there is lots alcohol on the brush. Brush this over the copper side from the pcb.
If this is done take a sheet kitchen cleaning paper and put this over the sill wet pcb.
Now brush over the kitchen paper so that it picks up the dirty alcohol that is on the pcb. If not clean the first time than repeat this again. Watch for clean teeth between the ic's
I always do a last time cleaning without the paper.. so I can see it is really clean.

Regards.

Ap

So I am looking to remove the oil from my hands,and the hard glass like flux from around the solder joints? And alcohol will dissolve the flux? I have heard of washing boards in warm water also?What does the flux add capacitance between pins?

[chemelec]

So I am looking to remove the oil from my hands,and the hard glass like flux from around the solder joints? And alcohol will dissolve the flux? I have heard of washing boards in warm water also?What does the flux add capacitance between pins?

Depending on Humidity, Solder Flux adds Resistance between Traces.
And this Flux will be on BOTH SIDES of the board as It goes through the Holes when Soldering.

I use a Kester 331 Solder. It is a Tin/Lead solder and it contains a Water Based Flux.
So to clean the board you just put it under a Warm Water Tap and rince it off good on BOTH Sides.

I wash my boards with ALL IC's and Trimpots on the board, than DRY it Good, before applying Power. (MOST parts are OK with Water)