Whites Surf PI schematic

[Vadim18]

Interesting VCO sound. Not a bad modification at all. I suppose with some tweaking, it can be made to work better at the lower frequencies with weaker targets. Overall, quite a good effort.

Hi dbanner! Thanx for your comment!

Yes, vco is not bad addition and it also can produce 50% duty cycle output.
However today this addition produce more noise than clear tone, so probably i will put some RC filter to smooth control voltage.
I think also to check active clamp at SAT in the nearest future, hope it make response between big and small targets cleaner.

[dbanner]

Interesting VCO sound. Not a bad modification at all. I suppose with some tweaking, it can be made to work better at the lower frequencies with weaker targets. Overall, quite a good effort.

[Vadim18]

Here is some of my unit fotos. Was completed in almost 4 years ago.






Op-amp VCO tests
SurfPI_VCO-test.zip

[Vadim18]

More info on the VCO Please ?

Just simple voltage controled oscillator with integrator (OP3_A in my circuit) and comparator (OP3_B), with square wave output - thats not my design. It has close to linear frequency swep from zero to 800 Hz, i limit upper frequency by using 3v3 zener diode at OP2_B feedback and also did that by adjusting capacitor C8. Also VCO in my circuit need some more audible than 1-20 hz start frequency, to hear weak signals but in my locations with mineralised ground i lose nothing)

[homefire]

More info on the VCO Please ?

[Vadim18]

My Surf Pi modification's

[Vadim18]

Hi Vadim18, you have a good working project, always good to hear of success with the surf PI, if you have any circuits that you can post about your mods please do so, so we can all learn about your machine.

Thanx fo reply Guru, i will do that as soon as possible.

[6666]

Hi Vadim18, you have a good working project, always good to hear of success with the surf PI, if you have any circuits that you can post about your mods please do so, so we can all learn about your machine.

[Vadim18]

This is not a problem at all, I think they can be proud of being posted on this forum.

[Vadim18]

Hi to all!




Time to write my first post at this wonderful forum)
I will try to be useful.


I build my version of Surf PI in 2016, it was a great start point to dive in world of pulse induction machines.
First start was not succesfull and at second time coil was not so good.

Now, with 14.5 cm coil i can clearly detect 23mm coin (1mm thin allu-bronse alloy) at 27 cm, untill it reaches 30 cm distance.


My coil: 290 uH, 1 Ohm, 14.5 cm
Damping resistor: 390 Ohm


My mod's:


1. I limit the bandwidth with 3 pico cap in series with feedback resistor at main amplifier stage, to get more S/N rate.


2. Modified the SAT path by simly doublling the order of filter, as result i reduce a low frequency noise and get more stable treshold


at hight gain. This modification also help to cut a little bit ground noise - main problem in this machine...


3. Added, a conventional VCO on lm358, to get more audible information about target.


4. Pull up power to nearly 5.5 volts at positive and negative rails by adding bias diode to pin 2 of 78l05 (with catode to ground!)


The main problem still ground noise, but in our location the are places with low ground mineralisations to.
I already read some forum threads and hopely try to make some mods later.

[kt315]

I would have asked you ... better if you also delete the photos of the kids, I don't think he asked permission to the parents to publish them, I don't know how it works in Ukraine or Lithuania, but in the rest of the world it's a question of privacy, they are minors, better if you cancel them!

fill your account. we must see your country in your profile if you do statements related to the kids.

[plinio]

I have deleted the sniping. Please stop.

I would have asked you ... better if you also delete the photos of the kids, I don't think he asked permission to the parents to publish them, I don't know how it works in Ukraine or Lithuania, but in the rest of the world it's a question of privacy, they are minors, better if you cancel them!

[dbanner]

DB, i can give you torrent file and you can load all soviet magazines RADIO for whole time, 38 GB.
can you give me YOUR torrent file on your magazine?

All EleKtor magazines are available free for download from here: https://www.americanradiohistory.com/Elektor.htm
I would be interested in Russian magazines, but I don't see myself downloading a 35GB file. Maybe you could make a smaller file with a best collection of the Russian magazines. The ones you consider to be outstanding or useful to our hobby.

[Carl-NC]

I have deleted the sniping. Please stop.

[kt315]

KT315, I have entered my country in my profile.
Here is a very nice cover of this magazine. It would be nice to blow up into wall poster size.

DB, i can give you torrent file and you can load all soviet magazines RADIO for whole time, 38 GB.
can you give me YOUR torrent file on your magazine?