Whites Surf PI schematic

[joop]

800 Hz is more than sufficient, no need to change it!

[daverave]

800 pps seems a bit low....i thought small rings are found better with higher frequency...i know whites tdi operates up to about 3000hz....im not sure if i should increase the frequency and the tx pulse on time...would it give better proformance on rings and better depth...or should i leave the detector as designed ????

[starmoml]

help

Hello Friend
my circuit have no sound and no reaction to the metal
2 ohm coil resistance

[kt315]

what is the actual pulse frequency of this unit

Eric Foster answers you, Dave... please visit his PI TECHNOLOGY forum... http://www.findmall.com/list.php?34

The metal detector is one of the primary workhorses of the treasure hunter, particularly of the hobbyist THer. There are three primary types of detectors. Frequency shift designs include beat frequency oscillator (BFO), phase-locked loop (PLL), and off-resonance. Induction balance (IB) encompasses transmit-receive (TR) and very low frequency (VLF) detectors, as well as two-box detectors that are sometimes referred to as RF (radio-frequency). Finally, there are pulse induction (PI) designs.
PULSE WIDTH. The width of each individual transmitter pulse. Depending on the detector and its intended application, the pulse width can vary between 50 microseconds (uS) and 1000uS. 50 to 150uS is usually the width for ring and coin size objects while wider pulses suit detectors designed for locating larger objects. A boat towed PI designed to look for cannons would likely use 1000uS. Examples are:- Whites Surfmaster 50uS, Deepstar 100uS, Aquapulse 300uS, Superscan and Aquapulse towed 1000uS.
PULSE FREQUENCY or PULSE REPETITION RATE. The number of times the transmitter pulse is repeated every second. The frequency affects the response speed, power consumption and interference rejection, although all of these are influenced by many other factors in the circuit design. Examples are:- Surfmaster 800 pulses per second (p.p.s.) Deepstar 3000 p.p.s. Aquapulse 170 p.p.s. Superscan 66 p.p.s.

[Mohamed Ghitas]

Surf Pi

Hello every one
i come back again
now i made new surf pi long surf pi by DIRCEU
but when i plug power nothing happens JUST silence
any help ??

[daverave]

i have completed the surf pi detector and just wanted to know what is the actual pulse frequency of this unit...also how would i increase power to the coil...what component would i change ????

[Falcon]

hi Falcon
from where did you get this PCB design ??
if you can post it here r send it to me in message i will be gratful
thanks in advance
Regards
Mohamed ghitas


Notes : i have your same prblem in distance and i cant solve it
see this from Geo

"Hello.
Today i finished the Suf on a pcb ordered from Silverdog.
The detector worked from first time but the sensitivity was not good. After a fine adjusting to delay and offset trimers it had the ability to detect a coin at 12.. 13 cm only. I saw that there was not response when i changed the tune potentiometer. So the problem was near it...
After some time i saw that with the resistors that Silverdog gives must use 100k potentiometer. BUT Silverdog writes at part list for surf at his site that the potentiometer must be 10K. I replaced it with 100k and all OK. Another very good PI detector for underwater detecting.

Regards"

it didnt work for me

Hi Mohamed Ghitas,
This PCB is available here in the forum, at the link below:

http://www.geotech1.com/forums/showthread.php?13810-Whites-Surf-PI-schematic/page21

Is in the post - 509 (page - 21) provided by Dirceu.
I will test the 100K pot.
Besides detecting little (2cm coins) can not silence, always a Beeepp ... continuous with a lower sound.
Your PCB is Silverdog?

[daverave]

maybe i will have to remove more turns...do you think at 20 turns i will run into problems ??? im not sure what type of resin i have...i just bought it from ebay some time ago..are they labelled as slow or fast curing ????

[Qiaozhi]

if i were to use 30 turns would i loose depth ???? seeing the coil is 8 ohms maybe the back emf would be smaller so sampling would be quicker ??? i want the coil to be sensitive so would i be better using 20 turns as you stated ???

The 30 turn coil will be slower because of the higher inductance and inter-winding capacitance. If you want a fast coil, then use 16 turns.

i have now 20 turns of 30 swg wire and the inductance i think is around 500 mH...i have used spiral wrap and the scotch shielding....is the shielding wrapped all around the full diameter of the coil apart from the usual 2" gap ???? also can anyone pls advise me on the resin that i put into the coil....will it warp the plastic coil housing as it cures...also how much hardner do i mix into the resin...i know very little about all this....im frightened to ruin my coil if i make a mistake.

I think you meant to say 500uH. A 500mH air-cored coil would be enormous.
Since you've already made the 20-turn coil, test this first to see if it's fast enough for your particular purpose.

Wrap the shield around the coil leaving a small gap (say 5mm) and connect the shield to GND. If you do not leave a gap, eddy currents can flow around the loop and completely destroy the sensitivity of the detector.

You can use resin to pot the coil, but make sure it's the slow curing type. Fast-curing epoxy will generate heat, as you found previously.

For initial testing of the coil, you can simply use hot glue.

[daverave]

i have now 20 turns of 30 swg wire and the inductance i think is around 500 mH...i have used spiral wrap and the scotch shielding....is the shielding wrapped all around the full diameter of the coil apart from the usual 2" gap ???? also can anyone pls advise me on the resin that i put into the coil....will it warp the plastic coil housing as it cures...also how much hardner do i mix into the resin...i know very little about all this....im frightened to ruin my coil if i make a mistake.

[Mohamed Ghitas]

Sorry for the delay
My motorcycle battery is 12V - 5 amp
My 20cm coil, 18 turns, 0.5 mm wire (24AWG) or 20cm, 18voltas wire 0.6 (23AWG) or 23.5 cm, 24 turns, 0.5 wire (24AWG). all with the same results.
5 ICL7660 pin voltage is equal to - 4.75V, and pin 8 is 5.1v +.
In NE555 pin 3 of the voltage is 11V (+ or -).
In 2N3906 between the collector and GND is "4.4V".
Adjusted the offset -> 0V on pin 6 of the NE5534 (as described in the forum) and remains so.
The tension in my coil is 0.56 V.
Do not know if it needs some more adjustment / setting / trick / secret, or some substitution of values, so I am sending a picture of how this my Surf Master at this time (with the updated values).[ATTACH]26266[/ATTACH][ATTACH]26267[/ATTACH]

hi Falcon
from where did you get this PCB design ??
if you can post it here r send it to me in message i will be gratful
thanks in advance
Regards
Mohamed ghitas


Notes : i have your same prblem in distance and i cant solve it
see this from Geo

"Hello.
Today i finished the Suf on a pcb ordered from Silverdog.
The detector worked from first time but the sensitivity was not good. After a fine adjusting to delay and offset trimers it had the ability to detect a coin at 12.. 13 cm only. I saw that there was not response when i changed the tune potentiometer. So the problem was near it...
After some time i saw that with the resistors that Silverdog gives must use 100k potentiometer. BUT Silverdog writes at part list for surf at his site that the potentiometer must be 10K. I replaced it with 100k and all OK. Another very good PI detector for underwater detecting.

Regards"

it didnt work for me

[daverave]

if i were to use 30 turns would i loose depth ???? seeing the coil is 8 ohms maybe the back emf would be smaller so sampling would be quicker ??? i want the coil to be sensitive so would i be better using 20 turns as you stated ??? also can you tell me if ordinary resin is good enough for potting the coil...i seem to remember many years ago when i was younger trying to make a detector coil and filling it with resin and the coil got hot throught the chemical process of the resin and warping the coil plastic...could you advise pls.

[Qiaozhi]

You can calculate coil induction if you stretch your coil to circle with coil calculator if you don't know if your LRC meter is malfunctioning... 30swg is 0.315mm
you need to input radius in metric (half diameter)
and no. of turns

www.geotech1.com/forums/attachment.php?attachmentid=13817&d=1290969584
extract and run coilcalc.htm

Actually there's a more accurate method than "bending" the elliptical coil into a circle. You can use the average of the two radii. Or simply add the two diameters together and divide by 4. In this case the answer is 6.75".

ive since wound a coil with 30 turns of 30swg wire the coil resistance is about 8ohms but my inductance meter i bought from china is a bit confusing...on the 200mH range it reads 01.1...and on the 20H range it reads 1.15 can anyone make sense of these readings ???? have i wound too many turns of wire ??? my coil is 15 x 12 inches dia.

For a coil radius of 6.75" (171.45mm) and 30 turns, the inductance should be 1.069mH, which is very close to what your inductance meter is measuring. I would recommend using between 16 and 20 turns. These two values will give 321uH and 492uH respectively.

[sdesic]

ive since wound a coil with 30 turns of 30swg wire the coil resistance is about 8ohms but my inductance meter i bought from china is a bit confusing...on the 200mH range it reads 01.1...and on the 20H range it reads 1.15 can anyone make sense of these readings ???? have i wound too many turns of wire ??? my coil is 15 x 12 inches dia.

You can calculate coil induction if you stretch your coil to circle with coil calculator if you don't know if your LRC meter is malfunctioning... 30swg is 0.315mm
you need to input radius in metric (half diameter)
and no. of turns

https://www.geotech1.com/forums/attachment.php?attachmentid=13817&d=1290969584

extract and run coilcalc.htm

[daverave]

ive since wound a coil with 30 turns of 30swg wire the coil resistance is about 8ohms but my inductance meter i bought from china is a bit confusing...on the 200mH range it reads 01.1...and on the 20H range it reads 1.15 can anyone make sense of these readings ???? have i wound too many turns of wire ??? my coil is 15 x 12 inches dia.