GOLDSCAN 5 SCHEMATIC QUESTION

[Orbit]

:лол:

[DonCaffeDelaSkobalj]

Hello Eric

You can contact me via e-mail if you want. We can talk about new input frontend with your time-code 12-4-4-4. All your designs are very good. We could improve input stage and rx stage, while keep your original design. About Rx at nano seconds time frame,OP slew rate and settling time are two opposite stuffs. I would point out for improving settling time, because we have deal with nanosecond pulses with very sharp front and back eadges and very fast transients.

Regards
Don

[DonCaffeDelaSkobalj]

Hi Don,
Goldscan5 was developed for nugget hunting as well as for beach hunting. Previous Goldscans had effective ground cancellation based on a development of mine in 1983 after a visit to Australia and which resulted in Goldscan 1. However, there are certain goldfield areas in Victoria, Australia, where the ground effect is particularly strong. Modifications were made along the line which culminated in Goldscan 5, A B, and C. with improved ground cancellation. The design was sold to Whites and continued with further upgrades to the TDi Pro and SL. and finally the TDi BeachHunter. I continued with Goldscan 6, which was a much more powerful detector designed for larger nuggets more deeply buried. Tests in the Victoria Goldfields were made and it proved to have a advantage over the competition in this respect. Introducing detectors in Australia that compete with home grown ones is an uphill struggle fraught with legal challenges, so the project was discontinued, although the methods I have used in cancelling viscous remanent magnetism (VRM) in the soil or rock predate any patents subsequently lodged for PI detecelopeoftors.

As to the detector I have that runs on the 12-4-4-4-4us ,timing, even if GB were added, would only be of use for fly spec nuggets. The range on the larger bits would be poor, as the Tx pulse is much too short and too small in amplitude. VRM has a different decay law to conductive targets and increases dramatically at short delays, and that could be a big problem. This proportional timing is useful though and has been used in a prototype nugget hunter where we have,say, a useful Tx of 50uS and upwards; and succeeding proportional delays and samples all under the control of a variable clock generator.

I agree that bi-polar pulse technology would be the way to go for future designs. It would also eliminate the small hysteresis effect that has been observed in some VRM studies.

Eric.

Thank you Eric.

There exist methods for improving amplitude of very short Tx pulse as is in 12-4-4-4 timing, for hunting larger bits of gold in Oz's soil. Not to complex modifications of Tx frontend will boost amplitude till 100 КWt in peak pulse power, ordinary at 50 ohms load or lower. Methods were widely used in particle accelerators.

Do you have envelope for VRM dacay law for golden areas in Victoria, Australia ? Variabile Tx pulse train inside main Tx pulse while keeping your inicial 12-4-4-4 timing code with super fast ns pulses integrated in main Tx pulse with properly set duty cycle. I think envelope of complex Tx excitastion curve, should follow inverse law of VRM decay curve, or maybe pseudo inverse. The best would be tests on a real Oz soil. Also amplitude boost should be controlled up or down to keep oversaturation of very small nuggets end eliminating soil hysteresis.

Regards
Don

[Ferric Toes]

Hi all

gScan_5 isn't definitely nugget hunting machine. Repetion rate is to low, Tx forward phase to long. Togetheer with non properly designed Tx stage AND non corectly choosen MOSFET is a main source of overheating damping resistor and great ammount of integrated noise in post-processing stages. Also a current consumptionis is to high for this class of PI machine.

As it was initially Eric design, i suggest newest Eric's TIME CODE 12-4-4-4-4 for the real NUGGET HUNTERS. It isn't an easy task.
Also GB timing must be tweaked on the highly mineralised ground. This all worth for mono pulse design. Further design for example gScan 6 should be bipolar nugget PI machine.

Regards
Don

Hi Don,
Goldscan5 was developed for nugget hunting as well as for beach hunting. Previous Goldscans had effective ground cancellation based on a development of mine in 1983 after a visit to Australia and which resulted in Goldscan 1. However, there are certain goldfield areas in Victoria, Australia, where the ground effect is particularly strong. Modifications were made along the line which culminated in Goldscan 5, A B, and C. with improved ground cancellation. The design was sold to Whites and continued with further upgrades to the TDi Pro and SL. and finally the TDi BeachHunter. I continued with Goldscan 6, which was a much more powerful detector designed for larger nuggets more deeply buried. Tests in the Victoria Goldfields were made and it proved to have a advantage over the competition in this respect. Introducing detectors in Australia that compete with home grown ones is an uphill struggle fraught with legal challenges, so the project was discontinued, although the methods I have used in cancelling viscous remanent magnetism (VRM) in the soil or rock predate any patents subsequently lodged for PI detectors.

As to the detector I have that runs on the 12-4-4-4-4us ,timing, even if GB were added, would only be of use for fly spec nuggets. The range on the larger bits would be poor, as the Tx pulse is much too short and too small in amplitude. VRM has a different decay law to conductive targets and increases dramatically at short delays, and that could be a big problem. This proportional timing is useful though and has been used in a prototype nugget hunter where we have,say, a useful Tx of 50uS and upwards; and succeeding proportional delays and samples all under the control of a variable clock generator.

I agree that bi-polar pulse technology would be the way to go for future designs. It would also eliminate the small hysteresis effect that has been observed in some VRM studies.

Eric.

[DonCaffeDelaSkobalj]

Hi all

gScan_5 isn't definitely nugget hunting machine. Repetion rate is to low, Tx forward phase to long. Togetheer with non properly designed Tx stage AND non corectly choosen MOSFET is a main source of overheating damping resistor and great ammount of integrated noise in post-processing stages. Also a current consumptionis is to high for this class of PI machine.

As it was initially Eric design, i suggest newest Eric's TIME CODE 12-4-4-4-4 for the real NUGGET HUNTERS. It isn't an easy task.
Also GB timing must be tweaked on the highly mineralised ground. This all worth for mono pulse design. Further design for example gScan 6 should be bipolar nugget PI machine.

Regards
Don

[6666]

you dont need to increase the tx pulse...you will drain your batteries a lot quicker....i made a 12" & 14" coil and my 14" coil has already gained a few inches in depth without touching the tx pulse.

Hi Dave, I have a 2003 pound coin, what sort of distance would you get that coin with your 14 inch coil ? thanks.

[peyman 74]

pcb that abanner(v13) put here someone made it ? is it correct ?

[peyman 74]

have you a idea to increase the deep in device to work very well with large coil?

[daverave]

you dont need to increase the tx pulse...you will drain your batteries a lot quicker....i made a 12" & 14" coil and my 14" coil has already gained a few inches in depth without touching the tx pulse.

[peyman 74]

hello , if we increase the tx pulse with , is it possible to use a larger coil ?

[Jose]

My coils are all made at home.
I use the Cat5 cable and the Scotch 24 tape for the shield, in addition to separation with plastic tape.
The inductance is from 300 to 350 uH, the resistance is from 2 to 2.5 ohms approximately.

[ispanyol2]

What kind of coil do you use? What is coil resistance. Thanks to everyone who is in trouble to answer my questions

[Jose]

Your writing seems logical, jose. Do you use current limiters in the mosfet feed. Or just resistance. It is possible to describe this part as Drawing.

I do not use current limiter, only the resistance of 1 ohms.
The resistance of 1M, which is seen in the image you published, seems to be 220K, in the existing schemes.
I use 12V, on my detector.
I enclose the scheme for better reference.
In red circle I indicate the values of the components, as it is in my self-built GS5.

[ispanyol2]

Your writing seems logical, jose. Do you use current limiters in the mosfet feed. Or just resistance. It is possible to describe this part as Drawing.

[Jose]

The damping resistance takes a lot of temperature, I install two rersistors in series and they work well.
The 1M residence, I think it's 220k as you can see in the published schemes, seems to be part of the pre-amplifier's 0 volt configuration.
The 1k resistance at the preamp input, use 2.2k, can be seen on the GS5 images.
You get a good sensitivity, better adjustment of the damping resistance, and less noise, if you use 2.2k.