Whites Surf PI schematic

[daverave]

I need some advice on my surf XX board.. Ive made an 11" coil with approximate inductance of 500uH, it had good depth but not stable at the beach, always causes false signal. i need to swing very very slow to avoid falses.. i'm using aluminium tape for shielding. if damping resistor is the problem, can anyone give tips for tuning the damping resistor correctly. ? thanks..

if you want to get the damping resistor correct then use a pot of around 1k 3 watt in place of your 390 ohm resistor and adjust until you get clean waveform without ringing then measure the resistance of adjusted 1k pot then replace with fixed resistor of the same value...the false signal could be caused by the detector responding to the wet sand....you may need to make the sample delay later so adjust the preset on the pcb....and make sure you fully screen the pcb with aluminium foil making sure the foil does not touch the pcb and connect the foil to ground via a wire to the ground connection on the pcb...use paper clip to connect wire to the foil.

[daverave]

was my info ok as no comment seen

[sukri01]

sorry dave, i couldnt try it now, father just passed away, ill report back when ive settled things around, many thanks for your help.

[daverave]

very sorry to hear about your father passing away....i know how your feeling as i lost my mother about 3 years ago and i still havent got over it and i guess that i never will...take care mate.

[farafero]

hi
http://www.geotech1.com/forums/attac...8&d=1389296508
Can I use other transistors instead BC337 and BC 556 ?

[daverave]

i guess you can as long that you get the transistor pin outs correct

[paku]

i have finish make spiral coil how to shiled this coil any one know

[bernte_one]

hello paku
well done

mix clear laquer or paint (acrylic or epoxi base) with graphit powder and use this as shield

if you dont want to by clear paint
use acetone mix this with styrofoam ( search Q-dope) and add graghit powder (you can measure resistor with meter around 200K setting)

[paku]

hello paku
well done

mix clear laquer or paint (acrylic or epoxi base) with graphit powder and use this as shield

if you dont want to by clear paint
use acetone mix this with styrofoam ( search Q-dope) and add graghit powder (you can measure resistor with meter around 200K setting)

allright thanks bernte_one
Best Regards, Paku

[paku]

how to make sound loud with this board

[Davor]

You can use a transformer from an old transistor receiver, and make sure to connect a speaker to a low impedance end. Works for me in another project.

[paku]

You can use a transformer from an old transistor receiver, and make sure to connect a speaker to a low impedance end. Works for me in another project.

can you show me some sample of picture

[Davor]

No problem, seek a transformer like the one in the picture, and measure windings resistance. The winding with lower resistance goes to the speaker, and the other one is connected to your machine instead of a speaker. In effect you get a speaker of a larger impedance, and because it is driven with current, it will be louder.
Alternatively you can seek a 50ohm loudspeaker and use it without a transformer.

[paku]

ok Thanks davor i will try find that transformer

[daverave]

with my surf pi detector i used two piezo elements in some ear defenders which i used as headphones and really loud volume without need of any transformer...nice sharp audio.