Full m/lab SD2000 schematics

[pustareka]

https://en.wikipedia.org/wiki/Johnso...3Nyquist_noise

охлаждение неутрино датчика = neutrino sensor cooling

[pustareka]

pcb 2000 ?

[pustareka]

NET PCB !

GAME OVAR !

[Andi68]

Whats up?

[kt315]

NET PCB !

GAME OVAR !

daverave has Goldscan 5. try ask him to give pisc of board. http://www.geotech1.com/forums/showt...ESHOLD-PROBLEM
we need new winter project of seeking gold nugget detector.

[Andi68]

We urgently need such a winter project

[bernte_one]

while thinking of the next problematical pi design, make any thoughts about a multifrequency detector and signal processing via µcontroller
this is a real next step in diy world

[au1]

earth field trimmers

A couple questions. I'm attempting to adjust the earth field trimmers and found the photo below in one of the SD threads which I think was posted by Mechanic.



Since my board isn't laid out the same I need to know the value of the resistor and it's connections. Do the trimmers affect only the sensitivity to earth field or do they also effect the overall sensitivity?

Another question. There is a 65pf capacitor in the TX section connected to pin 2 of the 4093 and GRND. Does this capacitor have any control over the point at which the front end receive fets turn on? If so, would there be any advantage to using a variable cap ?

Thanks!

[Mechanic]

Forget that picture.
Just use a ferrite magnet, I use a magnet from a small speaker about 2" diameter. Remove all metal from the magnet!

Bob it up and down in the center of your coil.

Cheers Mick

[au1]

IRF710

Thanks! Worked great. I'm in the process of installing the boards in a Hammond enclosure and found this picture on MLM's showing the irf710 mounted to the enclosure.




Apparently from what I can gather, the fet tab is isolated from the housing and the wire. I'm curious why they did it this way instead of either using a heat sink or laying it on the board. Does the wire just ground the enclosure?
Because of the foul weather here and the impracticality of moving 2 boards, a battery, headphones and a coil outside all my testing has been inside until I get it housed.
I have very good sensitivity but have noticed that the closer I get a target to the coil the detector screams. And oscillates a few times. I contribute this to being around a lot of emi ? But, if I touch the heat sink and repeat, the oscillations never happen. Smooth and quiet. Is it possible by mounting the fet as they did that does something similar to what my finger did? Any ideas?
Thanks

[waltr]

Thanks! Worked great. I'm in the process of installing the boards in a Hammond enclosure and found this picture on MLM's showing the irf710 mounted to the enclosure.

[ATTACH]45009[/ATTACH]


Apparently from what I can gather, the fet tab is isolated from the housing and the wire. I'm curious why they did it this way instead of either using a heat sink or laying it on the board. Does the wire just ground the enclosure?
Because of the foul weather here and the impracticality of moving 2 boards, a battery, headphones and a coil outside all my testing has been inside until I get it housed.
I have very good sensitivity but have noticed that the closer I get a target to the coil the detector screams. And oscillates a few times. I contribute this to being around a lot of emi ? But, if I touch the heat sink and repeat, the oscillations never happen. Smooth and quiet. Is it possible by mounting the fet as they did that does something similar to what my finger did? Any ideas?
Thanks

I will GUESS that they simply used the MOSFET mounting screw to also attach the Case grounding wire (from the PCB).
Unknown if this was the best place electrically to attach PCB ground to case or if just the most convenient and using one screw for two purposes (saving the cost of second screw & labor to install).

[Mechanic]

The fet is screwed to the case for a heatsink. You don't want to dissipate the heat on the board as it will cause problems.
And the tab needs to be insulated as it should have 180v on it.
As for where to ground, Well the 2000 took ground from the power input, the F1A4 from the audio board, the gp series took it from coil ground at the coil plug and the gpx series from the power input again.
At the end of the day as long as everything is reliably grounded, it should be ok.

Cheers Mick

[au1]

Hi Mick,
I removed the heat sink and found the noise level dropped, so my thinking is to isolate the heat sink and ground it. I found these ->
https://www.mouser.com/ProductDetail...afZweAbw%3d%3d
and ordered a couple.
I resized my board packing everything tight as I could and when I receive the enclosure the boards should slide right in leaving about 3/4" on each end so as not to interfere with my pots and switches. When I made the latest board I added some ground holes in various places thinking they might be useful.



Just to the lower right of the 710 I have 2 ground holes. One to ground the heat sink and the other to ground the enclosure.
The fet tab shows 179.7 +volts. It gets hot but not so much I can't keep my fingers on it.
Is there any info available as to how they "recycled" the power from the fet back to the battery on the later models? I'm thinking a HS/HV diode and a regulator
maybe.

Thanks for your help!

[Mechanic]

Make sure there is a plastic insulator for the screw hole too. It doesn't look like there is one in that kit.

Consider mounting the fet off the board and use some wires to connect it to the board. That way the boa4rd can move a bit and it wont break the fet or pads.

In the later models they have a switching power supply circuit that converts the +180v back to -15v and feeds it to the tank for the -15v tx.

[pustareka]

SD2000 CortanaZed 2007 г.