Led output for Surf PI

[ApBerg]

Hello Friends,
Made another version from the Surf PI, it is the long print version in a ‘dive’housing. The new option is the led indication as signal for find indication.
Not so hard to make, not a speaker as output but a hi bright led or even a luxeon type for even more light will work. The threshold works just like with a speaker, with the volume pot you can adjust the 20 mA for a normal led or even some more power for a luxeon type look at the max for the mpsa 13 and take care for the heat from that led. If you made the long print version you can cut the track that is coming from the 4066 to make the audio sound to the mpsa13. ( not that it is must )
You can dive this way without cables for audio….
Best regards.
Ap

[sm876]

Hello ApBerg,

very good job !!!

Did you make this modification on your Surf PI Vers. 1.2 ?
Do you know where I can find info on calibrate the MD
in particular about the 4 trimmer ?

Thanks
Stefano

[DIRCEU]

Hi! ApBerg


Well done. Congratulations.

What kind of battery have inside the detector?


Dirceu

[ApBerg]

Hello,

Stefano, Indeed I made this mods on the 1.2 long print, it is not hard to make, take te audio output and connect a led on it. Can only be done in two way's , if it not working... reverse te wire's, pherhaps connecting a resister from 8 to 22 Ohm in serie's ....
Dirceu, I use 8 batt's from 1.2V- 800mA accu's, in time I can make some detail photo's...

Best regards !

Ap

[sm876]

Hello,

Stefano, Indeed I made this mods on the 1.2 long print, it is not hard to make, take te audio output and connect a led on it. Can only be done in two way's , if it not working... reverse te wire's, pherhaps connecting a resister from 8 to 22 Ohm in serie's ....
Dirceu, I use 8 batt's from 1.2V- 800mA accu's, in time I can make some detail photo's...

Best regards !

Ap

thanks
I understand the mods for the led.
I have build the MD but I have very low result,
Probably I'm wrong on how to calibrate the trimmer and the pots (exclude audio!)
Could you please give me some hints on them ...

Reguards
Stefano

[ApBerg]

Hello Stefano,

1. The coil, wire around 0.5mm and for 20 cm coil some 18-20 turns, do not use to thin wire.

2. The offset adjustment , look at the dc opamp out, this has to be (no signal) dc zero.

3. The delay adjust, set it to reject thin gold, then set it just to detect gold again ! this is the best point for adjusting if you have "normal'' ground ( I think )

4. Use the IRF 9640 for power fet

5. The damping resistor some 390 ohms

6. Look at the total mA that the circuit is using, at no signal must be around 50mA.


What board have you made ? and what is the detection depth for a 1 Euro size coin (normal must be some 25 cm)

Best regards.

Ap

ps. Look at the posts that are (on this great forum) about the Surf master, lots more info !

[Esteban]

Appie, very nice design!

[sm876]

Hello ApBerg,

I've red the posts on Surf PI, but you give me more info to understand better the MD,
in particular I never found info un trimmer as you write.

I used 1 mm wire for the coil, with 356uH and 0.8 ohm,
so one problem could be in the coil.

I used a FQP12P20 instead of IRF9640 because I had it and because has similar parameter.
Now I try also irf9640.

Since normally use Kicad as ECAD, I re-draw the schematic and PCB version of your Surf PI 1.2,
which can be seen here http://thunting.com/smf/pi_designs_d...-t2838.60.html

Now I do not know if I can post here in the forum the same things,
if it were possible I would be happy to do it ... someone please let me know ...

The detection depth is very bad for me, abaut 12/15 cm with 20cent Euro.
Now I will try to make the change you suggest.

Thanks again.

Regards
Stefano

[hobbes_lives]

Stefano,

The stock Surf PI coil is 230uH, 1.37 ohms. ApBerg's coil recommendation of, "wire around 0.5mm and for 20 cm coil some 18-20 turns", is correct. I built an 11" coil (10.5" ID) for the Surf PI using 19 turns of 24AWG wire. It measured 226uH, 1.4 ohms.

With your coil parameters of 356uH, 0.8 ohms, you will likely not be able to sample at 15us. The decay curve will likely extend well past that point. Also, how did you shield the coil? Did you leave a gap in the shield?

The FQP12P20 seems like a good substitute, although some of the parameters indicate that it may be a little bit slower than the IRF9640.

I'd suggest to try another coil with the proper parameters, then try the adjustments as ApBerg has indicated.

BTW, do you have an oscilloscope?

[ApBerg]

Hello Friends,

Thanks Esteban ! In the past I made some more experiments with led's, with poor results. Now there are the Luxeon leds that have very strong results ( take care for your eyes !!) If you place a colored led in white nylon you can even see signal at sunny daylight. Minor point.. they can get hot if to must power is added.
Thanks Hobbes for helping, this is a nice forum !

Good luck all.

Ap

[sm876]

Hello hobbes_lives and ApBerg,

Now I will try to build a coil with the appropriate parameters you suggest me.
I'm sorry but I am beginning with the MD so
I don't understand the meaning of your questions about
"if I shield the coil and if I leave a gap in the shield?"
Could you please be more clear,
or could you please tell me where I can find info abaout that?
I made a classic coil (posted below) with a diameter of 23 cm,
then I attached the coil with 2 short cables directly to the PCB,
just for testing.

I have a question:
I read the posts in the forum, and I saw that everyone has a coil resistance much greater than mine, as is it possible?
Have I got to solder an extra resistor in serial with the coil?

Yes I have a digital oscilloscope, and I have test the output of the FQP12P20 (DRAIN) and I saw un impulse at 638 Hz of frequenzy.

I'm glad of this forum, all you are helping me a lot to understand the MD.

Thank you very much.

Regards
Stefano

[hobbes_lives]

Stefano,

You should definitely read the following article by bbsailor, it's an excellent article about coil building. You'll learn about the important coil parameters and shielding.

http://www.geotech1.com/pages/metdet...s/FastCoil.pdf

Regarding the resistance of your coil, reducing the gauge of the wire will increase the resistance. The parameters that ApBerg and I provided in the previous posts should get you there.

[sm876]

Stefano,

You should definitely read the following article by bbsailor, it's an excellent article about coil building. You'll learn about the important coil parameters and shielding.

http://www.geotech1.com/pages/metdet...s/FastCoil.pdf

Regarding the resistance of your coil, reducing the gauge of the wire will increase the resistance. The parameters that ApBerg and I provided in the previous posts should get you there.

Thanks for the info, i'm going to study the coil article ... i hope to understand ...
after I'll post the new result ...

Regards
Stefano

[ossamaussama]

white surf master

i try the led instead of speaker it work fine

and i found that the there is saturation opamp problem

so i put opamp offset adjustment in the last stage

dc stage
also i am thinking of gain control like surfmaster II

iam working now for convert the surfmaster to work like delta pulse

that is VCO using 555 timer

[ant]

Hi ApBerg and everyone

I'm new here but love what I've seen so far.

I'm waiting for a couple of kits from Silverdog, and in the meantime looking around for ideas on the housing. I love the design you have come up with here, but am wondering how you got the coil in there?

Did you cut the pvc? Wound the coil by feeding it thru? Sorry if this is a basic question, I'm quite new to it all. Also, How did you bend the PVC, with heat?

Thanks,
Ant.