Surf Pro Kit

[kt315]

Can I use copper braid from high quality coax as my shield? Been reading lot about shielding on the forum but no real answers. Some say this some say that. People say to use graphite powder and other day munu's only use it to cut on cost and that there is way better shielding material to use

yes, if you do low speed coil. not, if you do high speed coil. choice what coil you do.

[Tibuck19]

Can I use copper braid from high quality coax as my shield? Been reading lot about shielding on the forum but no real answers. Some say this some say that. People say to use graphite powder and other day munu's only use it to cut on cost and that there is way better shielding material to use

If you used 26AWG to bigger, there is no need for shielding the coil. unless you plan on detecting near homes, that has a lot EMI interference, besides, The surf Pi is more of a beach detector anyways right!

[dime196604]

Can I use copper braid from high quality coax as my shield? Been reading lot about shielding on the forum but no real answers. Some say this some say that. People say to use graphite powder and other day munu's only use it to cut on cost and that there is way better shielding material to use

[dime196604]

So, started this post and detector almost two years ago. Well life got busy and i got sick of messing with the surf pi. It sat back of the closet for a little over a year now, pulled it out last week ti give it another go. Originally i made a basket coil, that would only detect steel about 4in. Any coins was only 1in if i was lucky. So thats why i thought the detector was not working proper. So last week i threw together a cheap wire bundle coil about 220uh I used stranded wire about 3X as think as the inner strands of phone wire. Thought this wire would be too think. BUT the detector is alive now. I can detect a US penny at about 14in air test. US quarter at 15 and my gold wedding band at 12in. So needless to say the detector is alive and i am very happy with the outcome so far. Still gotta tune the damping to the coil yet but so far results are good. All this trouble shooting i did so long ago was for nothing. All it was, a crapy coil. If only i would have made one a year ago.

[Tibuck19]

Use an adjustable damping resistor tool:
10k pot in series with a 200R resistor, and a 2k resistor in parallel with both the pot and resistor. This will give you an adjustment range from 181R to 1672R.
Attach the one good channel of your oscilloscope to the output of the preamp, and adjust the pot until you achieve critical damping. Disconnect the adjustment tool and measure the final resistance. Replace with a fixed resistor that has the closest value.

THANK YOU loll

[Koala]

That's helpful advice. is there a extreme where I don't want to go with the delay? I have read here on the forum that u can make the MD not work by adjusting the delay wrong

If it's the same as the barracuda then yes there is enough adjustment in the delay to make the detector not work at all.

i wave a gold ring over the coil turn the delay one way until it starts to loose a lot o depth then the other way until it starts to chirp an not work too good your compromise setting will be somewhere between the two

[6666]

Here is an example of the type of targets you eliminate as you increase the delay.

[dime196604]

Delay is a tricky one as at one setting it is good for one type of target but useless on others. Make it best for the other types and those that were excellent are now useless.


As an example if I set the delay best for a gold ring its useless on a fibula. Get a selection of different targets you hope to find and adjust for best comprises.

Offset stays put on the Barracuda no need to re adjust.


Delay does alter with different coils.

That's helpful advice. is there a extreme where I don't want to go with the delay? I have read here on the forum that u can make the MD not work by adjusting the delay wrong

[Koala]

Now i have a question on sting the onboard delay trimmer. What is the best way to go about this. I have tried doing it by ear but i don't really hear a difference in signal strength. Is there another way to set the delay? Also after finding the perfect delay setting, should i go back and recheck the offset? Or will it stay the same once i have set the offset to 0v? I am close to being done with this project but not there yet.

Delay is a tricky one as at one setting it is good for one type of target but useless on others. Make it best for the other types and those that were excellent are now useless.


As an example if I set the delay best for a gold ring its useless on a fibula. Get a selection of different targets you hope to find and adjust for best comprises.

Offset stays put on the Barracuda no need to re adjust.


Delay does alter with different coils.

[dime196604]

ok thanks. I will have a look and keep u posted. Thanks for the help.

[FatBob]

Well if you look at my scope picture I have 2V vertical and 4us horizontal.

You could start with those settings and see if you can get something like my picture...

[dime196604]

I do not think I can tell the voltage range on my scope. So I could just have it on the wrong setting. The only thing I have used my scope for is setting modulation on AM transceivers. other then that I really don't have a clue how to use it. My scope it a old two channel 200Mhz tecktronics. only channel one works. Would you have any suggestions on what rang I should have my scope set it for adjusting the damping on my MD?

[FatBob]

Well if you miscounted and were at 2 instead of 6 you might get that picture.

Pin 6 being the output cannot go beyond the power supply rails. As you see in my
pic I have ~9V. I cannot tell the voltage range on your scope...

[dime196604]

You should be looking at the output of the first opamp and see something like this;
[ATTACH]36791[/ATTACH]

Bob, my scope pic was at pin six of ic NE5534. I'm not 100%, but i thought this was the output of the first opamp. Am i looking at the wrong place with my scope?

[FatBob]

You should be looking at the output of the first opamp and see something like this;