TGSL Tuning & troubleshooting

[dfbowers]

I have tried nulling and I have made 00,8 mV AC ... without power it says 00,6 mV AC
started from 300mV
it is good BUT I have detection range of 1-2 cm

While I was testing with RX coil off and voltmeter on about 2 minutes from start
detector went beep, beep, beep ...
3-4 times a second ... pots are not responding, when I changed position of coils then it stopped beeping.

Any help would be appreciated.
Is it coil or PCB ?
What do to next ?

That can be an indication of a dead battery. Also, make sure your speaker is far away from the coils.
Don't spend too much time on nulling, just find the deepest null, mechanically secure them and leave them alone. What type of cable are you using?
See post #5022 here: http://www.geotech1.com/forums/showt...-SABRE/page201

[sdesic]

I have tried nulling and I have made 00,8 mV AC ... without power it says 00,6 mV AC
started from 300mV
it is good BUT I have detection range of 1-2 cm

While I was testing with RX coil off and voltmeter on about 2 minutes from start
detector went beep, beep, beep ...
3-4 times a second ... pots are not responding, when I changed position of coils then it stopped beeping.

Any help would be appreciated.
Is it coil or PCB ?
What do to next ?

[sdesic]

TGSL EDU (from Silverdog kit) is finally all completed and assembled with coils
RX 26 ohm 6,62mH
TX 24,9 ohm 6,02mH
wound up on jig as described in manual
(isolated, than wraped in mylar - conductive side out (left 1-1,5 cm blank for break in faraday cage)
(maybe too much overlap - can it hurt ?)
and plain wire wound for shield connection for both coils and as finish one more layer of isolation tape)

connected two pots and switch
connected with usb cable to PCB folowing manual - grounded on coil and on PCB

tested on bench
I have max 8 cm on 1 EURO coin in air if I place coils together

when I switch to K2 i K3 connection I have no detection
tried pots at various positions

ballancing is not very clear for me
my voltmeter has scale for 200mV AC but I don't trust it ... no oscilloscope yet...

can someone please explain functions of switch K1,2,3 and pot DISK.
if switch is on disk pot works and if switch is on all switch is doing ...

[Davor]

If you want to get very precise just remove one turn to get below 6.5, as compacting the coil will increase inductance a bit.

[sdesic]

I am making coil for TGSL EDU.
Wound 107 turns on coil jig... standard dimensions from manual for TGSL Coil making
255x137 mm
0.25mm copper anameled wire
I have inductance of 6.53 mH and resistance of 27 ohms.
It is still on jig.
Is that OK ?
Can I remove it and get going with isolation and shielding ?

[o_shq]

HI DEAR
> PLZ IF U CAN HELP ME ABOUT SNIFFER XR 71 THAT I HAVE A PROBLEM WHEN I ASSEMBLAGE THE DEVICE
> I HAVE 3 PROBLEMS
> 1. WHEN I CONNECT THE LOOP THE FUSE BURN OUT I TRY TO FIND ANY SHORT I DIDN'T FIND ANY THING.
> 2. THEIR IS SEPARATION I DON'T KNOW THAT IN THE CCT. CARD OR IN J1 & J2 IT WORK Intermittently.
> 3. THE RANGE WITH 1 METER LOOP IS JUST 30 CM.
> I APPRECIATE UR RESPONSE SO MUCH & THANK YOU.
>

[Jerry]

Hi Jerry,, "my goal was to be able to set a steady background tone when searching for coins"

What do you get or need when you find a coin?



Is it personal preference that you want a tone on continuously in order to give the impression of working the machine right on the sens threshold ??
S

Hi Steve,

It is a personal preference which I think can give maximum depth out of a machine. However, since the TGSL is a motion only detector, just adding a threshold control did not give the desired results. I worked on it for quite a while last year until I happened on this old thread which showed that someone else had already tried this with about the same results. So I decided to give it a rest for a while.

http://www.geotech1.com/forums/showthread.php?14998-Silent-search-vs-threshold-tone

Jerry

[golfnut]

Hi Jerry,, "my goal was to be able to set a steady background tone when searching for coins"

What do you get or need when you find a coin?



Is it personal preference that you want a tone on continuously in order to give the impression of working the machine right on the sens threshold ??

S

[dfbowers]

I couldn't find the link to the latest, so here it is.
Don

[starmoml]

Hello. show me breakdown on the circuit schematic. PLEASE help me

[Jerry]

I happened upon this old thread started by Porkluvr in 2008 which sums up and sheds some light on what I was trying to do.

http://www.geotech1.com/forums/showthread.php?t=14998

It is interesting on how the same subject keep coming back from time to time.

Jerry

[Jerry]

Gee, you made a completely different approach. On the IGSL topic I replied to you with explanation about the TGSL opamp bias problem, and you already fixed that by the other approach. My suggestion was to go for FET input opamps instead. This works too - either the mountain comes to Muhammad or Muhammad goes to the mountain.

BTW, I found that replacing R43 with 680k works perfectly for me. Simulation says 750k would be even better, but I don't have any in my stash, and I cant buy any on my li'l island.

Sorry for the confusion. The above diagram (I will call it the Lobo Mod) was something that I had already done to my original TGSL which I was not completely happy with and was still looking for a better solution. Which is about the time you offered your thoughts.

I tried your suggestions on another TGSL and like the results. So now I have one TGSL with your mod and another one with the Lobo mod. I was hoping there would be some benefit of incorporating the two.

Both of these detectors are working very well, but I always am looking for things to tweak them a bit.

Thanks for the tip on R43. I will give that a try.

Jerry

[Davor]

Gee, you made a completely different approach. On the IGSL topic I replied to you with explanation about the TGSL opamp bias problem, and you already fixed that by the other approach. My suggestion was to go for FET input opamps instead. This works too - either the mountain comes to Muhammad or Muhammad goes to the mountain.

BTW, I found that replacing R43 with 680k works perfectly for me. Simulation says 750k would be even better, but I don't have any in my stash, and I cant buy any on my li'l island.

[Jerry]

Another thing I picked up on yesterday is my original attempt at the threshold modification to my original TGSL (Ivconic board) was actually working better than I realized. The picture below shows the change I made several months ago. This is the threshold circuit from other Tesoro products like the Lobo.

Originally, I was not happy with this mod because my goal was to be able to set a steady background tone when searching for coins. This is the reason why I proceeded to mod my second TGSL (EDU board) according to Davors suggestions.

What I accomplished with the EDU board is very nice Proportionate audio which is settable from a low volume to total saturation. However, there still is no background tone.

I took the original TGSL out to the test garden yesterday. By chance, I turned it on while the coil was about three feet off the ground and heard the very nice, stable background noise of the TGSL. No crackles or pops, just a nice tone. It took me a while, but I figured out the I had the threshold set to max and backing it off quieted the tone. However, when I lowered the coil to the ground, the tone also went away. The reason this was a surprise is I normally turn the detector on when the coil is close to the ground so had not heard that steady tone before. I thought my mod was not working.

I then learned that the area near the ground in which the tone would not be heard was controllable with the GEB setting, very similar to this video: http://www.youtube.com/watch?v=bhTtkGCisfQ

So my next step is to incorporate Davor's mods along with the threshold mode shown below. Hopefully this will combine the best of both detectors.

Jerry

[Jerry]

Try bobbing the coil over a real ground when fine tuning the ground balance. You'll be surprised how good it works.

So where is the catch?!

Easy. Ferrite has no conductivity, so a ground balance setting achieved using ferrite would be 90° sharp. Real ground has some conductivity, so it's vector is not exactly at 90° but a bit towards the real side, or more ohms on your GEB potentiometer. The biggest catch of all is that this vector angle will not change with elevation of a coil above ground, so bouncing the coil up and down will induce some voltage in a GEB channel if your ground balance is not zeroed against that particular soil. When you hit the bulls eye, your toy will be silent, and your targets just perfect.

That is what I normally do. I was just trying to give an indication of what direction I adjusted the GEB.

Jerry