Coil for Golden Scan 5

[popefreedom]

Hi everyone,
I posted this in another section of this forum, and it occurred to me that here is the right place to ask for help concerning my issue

My asking is this:

would anyone, please, give me some help concerning the coil for Golden Scan 5 ?
I mean where can I find its specifications: its diameter, the thickness and quality of the wires involved, and the number of the wire turns..etc

Please help me and be sure that I'm
thankful in advance to any reply

[kt315]

Popefreedom, have you GS5 in your hands? can you open the housing? can you cameradigit the pcbs inside? something you are able to share?

thank you

[Geo]

I have read that it is about the same with whites TDI. So search for coils for TDI.

[kt315]

Geo, a data is on schematic. I wait a reply. something is not passed from nothing. THIS IS THE RULE. russian constructor Koschkin did not make a tank T-34 from nothing at bare place. at first he went in US on meeting with american constructor Walter Christie, did learn his tank, would been back in USSR and then did T-34.
archive will be fill by new data and this is FIRST RULE MY FRIEND GEO

[Geo]

Hello KT315.
First... Happy Birthday .
Really i don't understand what you mean. Who is this that i have and don't give to you???


Regards

[Geo]

I have read that it is about the same with whites TDI. So search for coils for TDI.

KT315... this reply is for popefreedom, not for you



btw... would you like to see my notes for details of TDI coil???

[kt315]

thank you.

[popefreedom]

Hi Guru and everyone,
I'm so sorry for the long delay. I've been through a lot.
I hope you and the guys are still helpful.
In response to your reply to my last request, concerning the GS5 coil,
yes, I have GS5 in my hands, and here you are the photos of my device.
I tried to camera digit it from all angles.
Any inquiries, I'm ready.
I'm looking forward to seeing from you soon.
..............
You have my respect and best regards.

[kt315]

oohhh mama mija... thanks lots for real hi res pics, but this is not original GS5, this is DIY board using GS4 schematic.
this board is by guy 'master hunter' name. this guy certainly did never see GS5 in his life and not could to see.

[kt315]

Eric Foster's hard sweety dream... GS5's at makdonalds conveyor... like the hot dogs for everybody...

[greylourie]

This is not a Goldscan 5. This is a clone of the Goldscan 4. There is a pdf somewhere with the protel files (?) that were produced by a Vladimir ?.... This is his pcb layout. Think it ended up on some Turkish forum.

For coil data look in this thread http://www.geotech1.com/forums/showt...5479#post25479
Look for posts by the gurus who successfully built copies of this machine and coils. Alexismex, Jose' and Max.

[popefreedom]

Thanks. I appreciate your response.
Actually, A while ago I asked for the schematic for GS5, and it was sent to me electronically.
On the basis of this schematic I myself designed the device shown in the previous pics, and it worked.
You can't imagine how glad I am to finish this device. Anyway, whether the schematic shown in pics is for GS4 or GS5,
could you please help me out designing my coil for this device ?

[greylourie]

Thanks. I appreciate your response.
Actually, A while ago I asked for the schematic for GS5, and it was sent to me electronically.
On the basis of this schematic I myself designed the device shown in the previous pics, and it worked.
You can't imagine how glad I am to finish this device. Anyway, whether the schematic shown in pics is for GS4 or GS5,
could you please help me out designing my coil for this device ?

Look in the thread that I posted. Look at posts by Alexismex, Jose' and Max.

[kt315]

12345

PI Coil Lesson

Posted by: Eric Foster (---.ipt.aol.com)
Date: March 25, 2000 04:30PM

Hi All,
Below is a repost of an article I did a while back on my Tech forum.
"There are many factors that influence the design of a PI coil. However, let's decide on two starting parameters i.e. 100uS pulse width and 2kHz pulse rate. One very important factor is what the earliest sampling time is required to be, as this does have a major effect on the maximum useable coil inductance. The greater the inductance and the higher the current, the longer it takes to reduce the field to zero and the later the sample delay has to be. If you are designing a detector for beach and shallow water hunting a good minimum sample delay to aim for is 15uS. With the right components in the transmitter circuit you can then use a coil inductance of 300uH. I have found it best to wind the coil with 10/0.1 PVC insulated stranded wire (10 strand, 0.1mm strand diameter) as this minimises eddy currents generated in the wire cross section. For a 10in coil the winding resistance is about 4 ohms and with an additional 4.7 ohm 4W resistor in series (in the drive circuit) gives a coil time constant (L/R) of about 30uS. For a 100uS TX pulse width (3.3 times the coil TC) the current will have reached over 95% of its maximum value at switch off, which is a satisfactory situation.
Another important factor to decide at the outset is the type of battery and the required battery life. At 2kHz the current consumption with the above values will be about 250mA at 12V which really requires the use of 10 C cells as a minimum. You can of course design for less current and smaller batteries by using a shorter TX pulse, a higher inductance coil with higher series resistance but there will be some performance trade off. Some PI detectors, particularly earlier designs, do not use a series resistor in the coil circuit to limit the current. Is this case the pulse current is often limited by the coil inductance i.e. the current is switched off well before it has reached its final value which would be determined by the coil resistance. Alternatively, the pulse repetition rate can be lowered until the current is of an acceptable value. There are disadvantages to both of these techniques:- Inductance limiting results in the magnetic field still changing rapidly in a positive direction at the point of switch off. This can cause some signal loss due to switch on eddy currents cancelling those generated at switch off. In pulse frequency limiting, the response time and noise averaging of the detector may not be as good.
The shunt, or damping, resistor, will be determined by the resonant frequency of the coil plus stray and cable capacitance. Not being able to display formulae yet (hope to soon as scanner arrives on Monday) you could look up in a radio or electronic text book the formula for a critical damping resistor for an LC with a given resonant frequency. Or you could just try it experimentally. Start with 1k ohms and look at the receiver output on a scope. The receiver (again it depends what front end I.C. you use) should recover cleanly with no ringing before the point of sampling. Add more resistors in parallel until this is achieved. You should end up with maybe 500 ohms across the coil as described above. Use a good quality 0.5W metal film as the peak emf at switch off can reach several hundred volts and I have found that smaller wattage carbon film resistors can break down and go noisy. I have tried a cermet preset in series with a fixed resistor to give an easily variable adjustment but again the high voltage can cause burning at the wiper contact and eventual failure.
Eric.