Nautilus revisited

[dbanner]

Looks good I assume that you used glossy photo paper

Actually I ended up using low grade paper with minimal gloss. That's all that I could get.
But I pressed down hard with iron on maximum heat. I'm not ever going to go through such primitive method again. I will try more sophisticated method. It is called "order from China PCB"

[dbanner]

Dbanner,
I will be happy to see the actual completion of the project. Keep me informed.
Melbeta

I will. Thanks

[rickb]

This is how it is on the DMC-2B PCB, from which I reversed the scheme.

Understand this, I am not denigrating your efforts to get a working DMC-2B. I have read the pertinent posts several times, and understand the design decisions relating to detecting and recognizing the short phase and amplitude changes that make this detector different. However, the change to the input of the analog switch makes no sense. That's why I question the correctness of that part of the schematic

Are you working from the real thing or photos?

Anyone with facts is welcome to chime in.

[dbanner]

Understand this, I am not denigrating your efforts to get a working DMC-2B. I have read the pertinent posts several times, and understand the design decisions relating to detecting and recognizing the short phase and amplitude changes that make this detector different. However, the change to the input of the analog switch makes no sense. That's why I question the correctness of that part of the schematic

Are you working from the real thing or photos?

Anyone with facts is welcome to chime in.

The photos are absolutely unambiguous as to the arrangement of components at the 4066 inputs. It is high pass filter. I do not know the value of the capacitor. Therefore I cannot be sure as to cut-off frequency.
1nf gives 7.23khz,10nf gives 723hz,100nf gives 72hz.
Why implement high pass at inputs to gates is for expert to know, I am novice.
Maybe it gives detector a sharper response to targets.
If you see on photo(and other photos of foil side), it was no problem at all to trace this section of circuit board, so I am confident that it is correct.

[dbanner]

There they are, right next to red wire, and the two 22k right nearby.
If you care to look at foil side photos, you will see clearly that there is no doubt as to how they are connected.

[dbanner]

Maybe also this arrangement provides a small amount of phase shift. Perhaps this is the primary purpose and not high pass.
Experts, where are you?

[rickb]

The last thing you want is a high pass filter. Why accentuate the noise? The signal is a 14 Khz sine wave. Besides there is already an ac coupling cap at the output of the coil preamp. I can't see anything on the parts side to convince me. If anything I would say that the unknown caps go to ground to form a low pass filter, but I can't see enough from the 1 photo to say that.The series resistor, 4066, and .01 cap forms a sample and hold function to implement an envelope detector. The following 2 integrators and differentiator with the faster time constants is what provides the sharper response to small targets.
--------------------------------------------------------------------------------------
The above was written before I saw the backside of the board.

As far as the 22k res are concerned, they do appear to be grounded but I didn't trace out the series caps.
Phase shift? They did retard the control signal of the early versions lower switch, so maybe that's right.
If I wanted to duplicate the unique functionality, I would build Davor's IGSL and change some time constants. I might add the servos if necessary.

[Melbeta]

I am not an expert either, but John Earle was an expert on filters. So I will post what he once said in some technical documents. John Earle created the VariFilters for the Compass metal detector scanner models. This might give you the clue you need...
Melbeta

Quote:
"The basic difference in time response between target signals and ground signals can be thought of in terms of an alternating current frequency. The target signal are higher frequency, typically from 5 to 10 cycles per second (Hz), and the ground, for 'nice and proper' ground might be around 1 to 2 Hz."

"What we want a filter to do is typically reject the low frequency ground signal of 1 or 2 Hz and still pass the 55 to 10 Hz. target signal. In other words, we want a fairly steep side to the first filter in that it should pass the desired signal 100% of the time and reject any signal slightly lower in frequency with total rejection. A 2 filter section filter will not approach this kind of performance. A more sophisticated filter could give this kind of response but what happens is that another characteristic besides just frequency response enters the picture for steep sided filters, and that is the ringing characteristic of this kind of filter to continue pumping out signals after detection has ended. Early versions of motion detectors wanted to utilize the best and steepest filters (more than 4 filter sections) to make sure they got rid of ground signals. But, their ringing nature carries the signal on for a period of time that would indicate target presence over a distance of several feet!"

"An example of a very good filter, with steep sides and exhibiting high Q (remember 'Q' stands for quality of the filter) is a tuning fork or even a resonating pipe. When struck, these devices ring on for many cycles as the sound slowly dies away. They don't even need to be stuck, one can simply whistle or sing on exactly their resonant frequency and after several seconds they will be vibrating so that if the energizing whistle is stopped, then the tuning fork or pipe can be heard to continue on. This is a basic fact of all filters, electronic or even mechanical as illustrated."

"Relative to motion detection, the filter composed of just 2 simple RC filter sections will be adequate to remove moderate "nice and proper" ground signals and being what is called low Q, it will not ring noticeably so that targets are well defined, similar to our X100 in 'Sharp' mode. The disadvantage is that severe ground signals, especially if the ground is nasty and has sudden changes in mineral concentrations (not 'nice and proper'), will get through the filter and add to or subtract from the target signal. The result will be that sweeping in one direction it may decide it is a good target and totally reject it in the others direction."

"Adding more filter sections to make a 3 section filter increases the filters ability to get rid of the ground and it is the preferred characteristic in heavier ground iron areas. But, target definition will not be as precise because the higher Q and longer ringing of this type o filter will cause a signal trailing that will cause two close targets to appear to be one, but the chances of them being detected is much better than the simpler 2 section filter scheme. Thus we provide the operator with a choice, depending upon the performance he desires."

"Scanner Filters
The Scanner filter system consists of more than 2 section filters for better ground elimination than other "turn on and go" machines that almost exclusively use the 2 filter section type of simple filter. But, Compass has some additional proprietary electronic processing that eliminates the ringing that normally results from a higher Q filter. Therefore, the Scanner gives better ground elimination while maintaining good close target definition in the motion mode or Trashout mode. Compass refers to this electronically modified filter system as the 'Vari-Filter'."

[pustareka]

dbanner privet Nautilus rezult OK ? Redy for gold serch ? Katuska Nautilus https://www.geotech1.com/pages/metde.../US4293816.pdf now-how [/img]http://vash-ru.net/anker/b_tehnolog/datchik/andron/02.jpg[/img]

[dbanner]

Never completed the project, it was a bit too much and I decided it wasn't worth the effort. Maybe one day I will revisit it, but not anytime soon.

[homefire]

I have a OLD Decrepit Unit if anyone wants one REAL BAD . Some what beat up but was suppose to be functional when I received it. Make Offer. Nothing of value . LOL

[pustareka]

Never completed the project, it was a bit too much and I decided it wasn't worth the effort. Maybe one day I will revisit it, but not anytime soon.

Thank you !