Yet another Surf PI in the fleet :)

[brucester]

Hi all,

Just soldered up my surf pi kit, plugged in the batteries and it worked first time. Havent touched the pots or anything so still need to learn how to tune it. But i get 12cm on a small coin and 30cm on an aliminium can using a 10cm test coil. That is around 3 times better than the Russian Pirate

Quick thanks to the people who made the surf pi possible. Very professional kit, simple and easy and works first time.
I didnt clean the board or tune it so results may improve.

Poor video quality from my mobile phone :P Turn your volume down, this thing is 29 times louder than the russian pirate :P

[joop]

It is a great detector, finished mine yesterday evening...

Make a bigger coil, the one you are using looks rather small. It will give you a lot more depth.

[brucester]

Will do Joop, thats just my test coil

Anyone have any recomendations on what is optimial size and inductace for coin hunting on the beach?

I'm guessing 250-300uH at around 11" diameter?

Cheers

[ApBerg]

Nice if there is succes !

Both are after electronic designs from White's, very efficient ..parts/result.. !!

Power consumption is low ( ca 50mA ), if you look at other disigns ... most eat 2 time's more current (100mA ).

It is a nice tought to make a good sensetive PI detector for a 9V batt. that takes around 25-30 mA, I am looking for low current parts so that can be done
Also tray to find the best pulse rate and time on for the Transmiter Fet so power consumtion is low and has still has a good 'magnetic, effect.

Some advice.... keep it simple.. ?


Best regards.


Ap

[bernte_one]

Appies pcb design make ist perfect!

best one i have seen last weeks was the one from bravodenisou
look on yt 40cm in air for an €-coin (but with some little easy mods)

have fun

[6666]

the one from bravodenisou

Do you have any more details on this please ?

[N1PS]

Here is another Surf Pi, Silverdog version. See video link. I'm getting some noise that I cannot seem to get rid of. I have made a couple different coils, the last one a shielded type. Range is not what it should be I don't believe. I cannot completely quiet the audio. Looking at the garbage on the scope...its what I would expect. Functionally, the MD works. The offset pot adjusts correctly. The delay pot (I brought that out to the control panel) works as expected. I added a number of ferrite beads on the wiring around the board, except the pots. The case is aluminum.

It could be just noise pick-up by the search coil, which is a bunched coil type, about 350 uH. I wish to try another shielded coil using copper tape, but I don't have any at the moment.

Anyway, I would like some ideas from anyone who is pretty familiar with the design.

[brucester]

perhaps try it in a different room or a different house :P

[Qiaozhi]

Here is another Surf Pi, Silverdog version. See video link. I'm getting some noise that I cannot seem to get rid of. I have made a couple different coils, the last one a shielded type. Range is not what it should be I don't believe. I cannot completely quiet the audio. Looking at the garbage on the scope...its what I would expect. Functionally, the MD works. The offset pot adjusts correctly. The delay pot (I brought that out to the control panel) works as expected. I added a number of ferrite beads on the wiring around the board, except the pots. The case is aluminum.

It could be just noise pick-up by the search coil, which is a bunched coil type, about 350 uH. I wish to try another shielded coil using copper tape, but I don't have any at the moment.

Anyway, I would like some ideas from anyone who is pretty familiar with the design.

PIs are notoriously noisy when tested indoors, and the instability on your audio output sounds quite normal. If you re-orient the coil, you should notice the instability will change, indicating that this is external interference. When you use it outside you will see a big difference.

[N1PS]

TNX. The location is my radio shop in the basement...so...did expect some noise as it is a PI. When the snow melts I'll try it outside. Just got 3 ft of snow yesterday....so it'll be a while.

My first MD and its been fun. I made a crude shielded coil but will attempt a better model. But I think the noise is EM and not E field. Kind of curious what the noise is. I did notice the changes with re-orienting the coil as you noted. I ruled out common mode noise being picked up by the coax (RG8X). But I am a novice in respect to MDs. Have really enjoyed the forum and site. I bought this Surf Pi a couple years ago and finally had a chance to put it together.

Cheers...
Peter

[brucester]

A couple of years ago? :P You're patient. Mine was soldered up 2 hours after it came out of the mailbox :P

I am testing mine indoors next to my computer, tv, wireless router, microwave etc etc and dont get noise with an unshielded coil.

Do you run a generator or live near a power station? :P

Oh well, if u can wait 2 year then waiting for the snow to melt wont be a big deal :P

[bernte_one]

the one i mean
http://www.youtube.com/watch?v=-jsbQ11ZBQE

img191.imageshack.us/img191/3131/testsurfschematic.jpg

regards

[dfbowers]

TNX. The location is my radio shop in the basement...so...did expect some noise as it is a PI. When the snow melts I'll try it outside. Just got 3 ft of snow yesterday....so it'll be a while.

My first MD and its been fun. I made a crude shielded coil but will attempt a better model. But I think the noise is EM and not E field. Kind of curious what the noise is. I did notice the changes with re-orienting the coil as you noted. I ruled out common mode noise being picked up by the coax (RG8X). But I am a novice in respect to MDs. Have really enjoyed the forum and site. I bought this Surf Pi a couple years ago and finally had a chance to put it together.

Cheers...
Peter

Peter,

Yea, that's pretty typical of indoor testing. Just to prove that your noise is being picked up by the coil, wind a test coil and bend it into a figure "8". Almost all your noise should disappear.
Don

[N1PS]

b

A couple of years ago? :P You're patient. Mine was soldered up 2 hours after it came out of the mailbox :P
I am testing mine indoors next to my computer, tv, wireless router, microwave etc etc and dont get noise with an unshielded coil.

Do you run a generator or live near a power station? :P

Oh well, if u can wait 2 year then waiting for the snow to melt wont be a big deal :P

Yep....had some other projects in front of it and friends kept bringing me radios to work on.....actually power line noise is quite good here. I operate AM (ancient modulation) on HF on several freqs with the ham stations and have no issues with power line noise. Great on your noise-free location. I'm still not 100% sure my noise is not my fault!!!

Don....that is a good idea. I ran the output into a resistor actually....no noise. I did try shutting off most of the AC near the bench. I noted the florescent lighting contributed to it (shocking discovery ). The noise is rather random, unstable and at low frequencies. The amplitude is of a spike nature (short durations). I'm more curious than troubled by it. Don't plan to search for treasure in my basement however. One way to possibly limit the noise - if its not a layout issue - would be to filter the audio and convert to a DC level. Then use a VCO to control the audio like a 555 I have seen in some MDs. Kind of a limiter using longer time constants. May or may not work.

So maybe the PI will be good noise detector? More work to do....and the snow needs to go away.

TNX for the comments.

Peter

[dfbowers]

Noise is a frustrating problem when working on some of these projects. If you read some of the TGSL threads, Simon Baker actually went on a Quest to find a location to verify a theory on detector performance and noise. With the TGSL project noise can manifest itself by lack of detecton range. It was not until he took a drive deep into the countryside until he was able to prove it to himself..

I finished a pair of IDXs a short time ago and had trouble with all of my coils (so I thought).. I could not run the sensitivity higher than 25 percent or so.. Just wobbling the coil slightly would cause false signals even in my back yard. THEN.. I took the IDX to a large field far away from my house and to my amazement I could run it wide open and it was absolutely quiet and stable!! I don't worry too much about noise problems when building anymore as I'm tired of banging my head on the workbench trying to figure it out
Good luck with the Surf Pi Peter. It's a nice project.

Don..