SD2000 Front end

[external9]

sd2000

hello Would explore how useful this is the metal detector?

[eclipse]

At least we know the schematic is correct, which is good ...

[1843]

1843 did you use the same components as those on the schematic
some of them like LT1057 have very good parameters and if you use
alternative the circuit could suffer from noises from such components
I also want to build the it, but I am novice, don't know if i could do it.
I am making board for it, 3 days just the power supply part ready

No! As I said the mine had many difference.... I used an LT1054 for power supply,
LF356 instead of LT1057... etc.

Best regards,
1843

[eclipse]

1843 did you use the same components as those on the schematic
some of them like LT1057 have very good parameters and if you use
alternative the circuit could suffer from noises from such components
I also want to build the it, but I am novice, don't know if i could do it.
I am making board for it, 3 days just the power supply part ready

[gef12]

Ye roger that .. I would have more benefit with motion mode as it gives me a good idea of where small targets lie .. especially nuggets... just cant visuallize how a non-motion would work or in what scenario ... have only used motion md's
thanks anyways

[1843]

hi
I dont suppose there is a sd2000 pcb in the making ...
Good try at the sd2000 on breadboard ..now i know I shouldnt try it as yet..
Have you try shielding the front end stage ?? or anything else ??
Anyways thanks

Hi,
No, I didn't shield anything. In fact when I saw it works in motion mode, didn't try anymore on it... I like non-motion MDs...

Best regards,
1843

[putrechigi]

hi

hi at all
see this video peraps is intresting for you

http://www.youtube.com/watch?v=XCKThqg7h5E

best reguards

[Aziz]

this one looks like 3 in parallel,

in one package, very low noise,

very high capacitance, very large die.

http://www.interfet.com/pdf/P_NJ3600L.pdf

Thanks JC1,



so we can reduce the input resistors + pre-amp resistors to lower the resistor noises.

I will start soon making some noise analysis on:
- different power supplies
- pre-amps
- coils and coil shieldings

I will also take milliWatt®™ PI coil pulses into account to reduce inherent noise and mineral soil magnetization.

Aziz

3

this one looks like 3 in parallel,

in one package, very low noise,

very high capacitance, very large die.

http://www.interfet.com/pdf/P_NJ3600L.pdf

links

Here are some links on IntraFet low noise devices.

notice the different noise, capacitance and die sizes.

now to get lower noise than the lowest one here you

would need to start paralleling them.

http://www.interfet.com/pdf/P_NJ450L.pdf

http://www.interfet.com/pdf/P_NJ903L.pdf

yes

I have one more goody for you and others:

A Low Noise Amplifier for Phase Noise Measurements

http://www.wenzel.com/pdffiles1/pdfs/lowamp.pdf

Almost same principle. But here using two fets parallel to reduce noise. This could be even better.


Aziz

Hi Aziz,

Yes two or more of the same type in parallel will reduce noise.

Over one of the same type.

If you check the data sheets on FETs you will find that the

lower noise devices generally have higher gate capacitance Cgs.

why? because they are physically larger dies in the package,

i.e. in effect multiple FETs in parallel just made as one large one.

now the silicon can also be thicker and thinner also causing a change

in capacitance but in general you will find what I said to be the case.

The drain current required is also usually higher as well just as you would

need to double the current through a single drain resistor to use two FETs.

[ZED]

Caps

At a risk of saying the obvious.

Dont forget to put bypass caps on all the chips,especially the preamps.

Zed

[Aziz]

Hi Aziz,

Yet another good find Aziz,

good work, and your coil stuff

is good too.

I have one more goody for you and others:

A Low Noise Amplifier for Phase Noise Measurements

http://www.wenzel.com/pdffiles1/pdfs/lowamp.pdf

Almost same principle. But here using two fets parallel to reduce noise. This could be even better.


Aziz

[gef12]

Hi gef,

I completed the my SD2000.... It works very unstable because of the breadboard and internal noises... it detects a gold ring at 12cm...
This machine must be made on pcb to get the best performance.

Regards,
1843

hi
I dont suppose there is a sd2000 pcb in the making ...
Good try at the sd2000 on breadboard ..now i know I shouldnt try it as yet..
Have you try shielding the front end stage ?? or anything else ??
Anyways thanks

good find

Hi Aziz,

Yet another good find Aziz,

good work, and your coil stuff

is good too.